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Dicentrine is preferentially antagonistic to rat aortic than splenic alpha 1-adrenoceptor stimulation

Mustafa MR, Achike FI

Acta Pharmacol Sin, 2000 Dec;21(12):1165-8.
PMID: 11603294

Dicentrine is a known alpha 1-adrenoceptor antagonist, but its alpha 1-adrenoceptor subtype selectivity has not yet been determined. We therefore, investigated the putative alpha 1-adrenoceptor subtype selectivity of this agent.

Matched MeSH terms: Aorta, Thoracic/drug effects*
Chronic treatment with flavonoids prevents endothelial dysfunction in spontaneously hypertensive rat aorta

Machha A, Mustafa MR

J Cardiovasc Pharmacol, 2005 Jul;46(1):36-40.
PMID: 15965352

Flavonoids are known to possess cardioprotective properties. Vascular endothelial function is a surrogate marker for cardiovascular diseases, including hypertension. We have studied the effects of chronic flavonoid treatment on vascular endothelial functions in spontaneously hypertensive rats (SHR). Starting from 6-7 weeks old, SHR were given flavonoids (baicalein, flavone, or quercetin) orally (10 mg/kg, once daily) to the SHRs for 4 weeks. Aortas from all the flavonoid-treated animals showed remarkably higher endothelium-dependent relaxations to acetylcholine, to a similar extent as those pretreated with the angiotensin-converting enzyme inhibitor, captopril. However, in contrast to other experimental groups, flavone pretreatment also enhanced the endothelium-independent relaxations to sodium nitroprusside. In addition, treatment with either flavone or quercetin induced a significant attenuation in systolic blood pressure of the hypertensive animals. The present results suggest that chronic treatment with the flavonoids (baicalein, flavone, and quercetin) preserves vascular endothelial functions in hypertensive animals through several possible actions, including increasing endothelial nitric oxide production and bioavailability and reduction in blood pressure.

Matched MeSH terms: Aorta, Thoracic/drug effects*
Vasodilator effect of Phlomis bracteosa constituents is mediated through dual endothelium-dependent and endothelium-independent pathways

Khan AU, Ullah R, Khan A, Mustafa MR, Hussain J, Murugan DD, et al.

Clin Exp Hypertens, 2012;34(2):132-9.
PMID: 21967029 DOI: 10.3109/10641963.2011.601383

This study describes the vasorelaxant potential of some pure compounds isolated from Phlomis bracteosa L. marrubiin, phlomeoic acid, and two new constituents labeled as RA and RB. In rat thoracic aortic rings denuded of endothelium, marrubiin, phlomeoic acid, RA, and RB caused relaxation of high K(+) (80 mM) and phenylephrine (1 μM)-induced contractions at the concentration range of 1.0-1000 μg/mL. Marrubiin, phlomeoic acid, RA, and RB concentration dependently (3.0-10 μg/mL) shifted the Ca(++) curves to the right obtained in Ca(++)-free medium. The vasodilator effect of marrubiin, phlomeoic acid, RA, and RB was partially blocked by N(ω)-nitro-L-arginine methyl ester in endothelium-intact aorta preparations. These results reveal that P. bracteosa constituents: marrubiin, phlomeoic acid, RA, and RB exhibit vasodilator action occurred via a combination of endothelium-independent Ca(++) antagonism and endothelium-dependent N(ω)-nitro-L-arginine methyl ester-sensitive nitric oxide-modulating mechanism.

Matched MeSH terms: Aorta, Thoracic/drug effects
Fulltext A Pharmacological Examination of the Cardiovascular Effects of Malayan Krait (Bungarus candidus) Venoms

Chaisakul J, Rusmili MR, Hodgson WC, Hatthachote P, Suwan K, Inchan A, et al.

Toxins (Basel), 2017 03 29;9(4).
PMID: 28353659 DOI: 10.3390/toxins9040122

Cardiovascular effects (e.g., tachycardia, hypo- and/or hypertension) are often clinical outcomes of snake envenoming. Malayan krait (Bungarus candidus) envenoming has been reported to cause cardiovascular effects that may be related to abnormalities in parasympathetic activity. However, the exact mechanism for this effect has yet to be determined. In the present study, we investigated thein vivoandin vitrocardiovascular effects ofB. candidusvenoms from Southern (BC-S) and Northeastern (BC-NE) Thailand. SDS-PAGE analysis of venoms showed some differences in the protein profile of the venoms.B. candidusvenoms (50 µg/kg-100 µg/kg, i.v.) caused dose-dependent hypotension in anaesthetised rats. The highest dose caused sudden hypotension (phase I) followed by a return of mean arterial pressure to baseline levels and a decrease in heart rate with transient hypertension (phase II) prior to a small decrease in blood pressure (phase III). Prior administration of monovalent antivenom significantly attenuated the hypotension induced by venoms (100 µg/kg, i.v.). The sudden hypotensive effect of BC-NE venom was abolished by prior administration of hexamethonium (10 mg/kg, i.v.) or atropine (5 mg/kg, i.v.). BC-S and BC-NE venoms (0.1 µg/kg-100 µg/ml) induced concentration-dependent relaxation (EC50= 8 ± 1 and 13 ± 3 µg/mL, respectively) in endothelium-intact aorta. The concentration-response curves were markedly shifted to the right by pre-incubation with L-NAME (0.2 mM), or removal of the endothelium, suggesting that endothelium-derived nitric oxide (NO) is likely to be responsible for venom-induced aortic relaxation. Our data indicate that the cardiovascular effects caused byB. candidusvenoms may be due to a combination of vascular mediators (i.e., NO) and autonomic adaptation via nicotinic and muscarinic acetylcholine receptors.

Matched MeSH terms: Aorta, Thoracic/drug effects
Vasorelaxant activities and the underlying pharmacological mechanisms of Gynura procumbens Merr. leaf extracts on rat thoracic aorta

Iqbal Z, Bello I, Asmawi MZ, Al-Mansoub MA, Ahmad A, Jabeen Q, et al.

Inflammopharmacology, 2019 Apr;27(2):421-431.
PMID: 29185178 DOI: 10.1007/s10787-017-0422-4

Previous studies have investigated the cardiovascular activity of Gynura procumbens Merr. single-solvent extracts. The objective of this study was to evaluate the in vitro vasorelaxant properties and the underlying pharmacological mechanisms of serial extracts and fractions of Gynura procumbens (GP). The leaves of GP were serially extracted with petroleum ether, chloroform, methanol and water using the maceration method. Suspended aortic ring preparations were pre-contracted with phenylephrine (PE 1 µM), followed by cumulative addition of GP extracts (0.25-3 mg/mL). The petroleum ether extract (GPPE) was the most potent among the four extracts. Pre-incubation of endothelium-intact aorta with atropine (1 µM), indomethacin (10 µM), methylene blue (10 µM), propranolol (1 µM) and potassium channel blockers such as TEA (1 µM), glibenclamide (10 µM), 4-aminopyridine (1 µM) and barium chloride (10 mM) had no effect on GPPE-induced vasorelaxation. The vasorelaxant effect of GPPE was partly diminished by pretreatment of aortic rings preparations with L-NAME (10 µM) and even more so in endothelium-denuded aortic rings, indicating a minimal involvement of endothelium-dependent pathway in GPPE-induced vasorelaxation. The calcium-induced vasocontractions were antagonized significantly and concentration-dependently by GPPE in calcium free and high potassium medium. These results illustrate that Ca2+ antagonizing actions of GPPE in rat isolated aorta are comparable to that of verapamil and may be mainly responsible for its vasodilation effect. The antioxidant activity of GPPE supports its vasorelaxant effect by attenuating the production of deleterious free radicals and reactive oxygen species in the vasculature.

Matched MeSH terms: Aorta, Thoracic/drug effects*
The effects of palm oil tocotrienol-rich fraction supplementation on biochemical parameters, oxidative stress and the vascular wall of streptozotocin-induced diabetic rats

Budin SB, Othman F, Louis SR, Bakar MA, Das S, Mohamed J

Clinics (Sao Paulo), 2009;64(3):235-44.
PMID: 19330251

OBJECTIVE: This study examined the effects of palm oil tocotrienol-rich fractions on streptozotocin-induced diabetic rats.
METHODS: Animals were divided into three groups: (i) normal non-diabetic (NDM), (ii) diabetic treated (tocotrienol-rich fractions - TRF) and (iii) diabetic untreated (non-TRF). The treatment group received oral administration of tocotrienol-rich fractions (200 mg/kg body weight) daily for eight weeks. The normal non-diabetic and the diabetic untreated groups were fed standard rat feed. Blood glucose and lipid profiles, oxidative stress markers and morphological changes of the thoracic aorta were evaluated.
RESULTS: Tocotrienol-rich fractions treatment reduced serum glucose and glycated hemoglobin concentrations. The tocotrienol-rich fractions group also showed significantly lower levels of plasma total cholesterol, low-density lipoprotein cholesterol, and triglyceride, as compared to the untreated group. The tocotrienol-rich fractions group had higher levels of high-density lipoprotein cholesterol, as compared to the untreated group. Superoxide dismutase activity and levels of vitamin C in plasma were increased in tocotrienol-rich fractions-treated rats. The levels of plasma and aorta malondealdehyde + 4-hydroxynonenal (MDA + 4-HNE) and oxidative DNA damage were significant following tocotrienol-rich fractions treatment. Electron microscopic examination showed that the normal morphology of the thoracic aorta was disrupted in STZ-diabetic rats. Tocotrienol-rich fractions supplementation resulted in a protective effect on the vessel wall.
CONCLUSION: These results show that tocotrienol-rich fractions lowers the blood glucose level and improves dyslipidemia. Levels of oxidative stress markers were also reduced by administration of tocotrienol-rich fractions. Vessel wall integrity was maintained due to the positive effects mediated by tocotrienol-rich fractions.

Matched MeSH terms: Aorta, Thoracic/drug effects*
The effects of heated vegetable oils on blood pressure in rats

Jaarin K, Mustafa MR, Leong XF

Clinics (Sao Paulo), 2011;66(12):2125-32.
PMID: 22189740

OBJECTIVES: The goal of this study was to determine the possible mechanism that is involved in the blood pressure-raising effect of heated vegetable oils.
METHODS: Adult male Sprague-Dawley rats were divided into 11 groups; the control group was fed with rat chow, and the other groups were fed with chow that was mixed with 15% weight/weight palm or soy oils, which were either in a fresh form or heated once, twice, five, or ten times. Blood pressures were measured at the baseline and throughout the 24-week study. Plasma nitric oxide levels were assessed prior to treatment and at the end of the study. Following 24 weeks, the rats were sacrificed to investigate their vascular reactivity using the thoracic aorta.
RESULTS: Palm and soy oils had no detrimental effects on blood pressure, and they significantly elevated the nitric oxide contents and reduced the contractile responses to phenylephrine. However, trials using palm and soy oils that were repeatedly heated showed an increase in blood pressure, enhanced phenylephrine-induced contractions, reduced acetylcholine- and sodium nitroprusside-induced relaxations relative to the control and rats that were fed fresh vegetable oils.
CONCLUSIONS: The blood pressure-raising effect of the heated vegetable cooking oils is associated with increased vascular reactivity and a reduction in nitric oxide levels. The chronic consumption of heated vegetable oils leads to disturbances in endogenous vascular regulatory substances, such as nitric oxide. The thermal oxidation of the cooking oils promotes the generation of free radicals and may play an important contributory role in the pathogenesis of hypertension in rats.

Matched MeSH terms: Aorta, Thoracic/drug effects*
Effects of ascorbic acid on impaired vascular reactivity in aortas isolated from age-matched hypertensive and diabetic rats

Ajay M, Mustafa MR

Vascul Pharmacol, 2006 Aug;45(2):127-33.
PMID: 16807125 DOI: 10.1016/j.vph.2006.05.001

Impaired vascular reactivity is a hallmark of several cardiovascular diseases that include hypertension and diabetes. This study compared the changes in vascular reactivity in age-matched experimental hypertension and diabetes, and, subsequently, tested whether these changes could be affected directly by ascorbic acid (10 microM). Endothelium-derived nitric oxide (NO) modulation of ascorbic acid effects was also investigated. All the experiments were performed in the presence of a cyclooxygenase inhibitor, indomethacin (10 microM). Results showed that the endothelium-dependent and -independent relaxations induced by acetylcholine (ACh) and sodium nitroprusside (SNP), respectively, were blunted to a similar extent in isolated aortic rings from age-matched spontaneously hypertensive (SHR) (R(max): ACh = 72.83+/-1.86%, SNP = 96.6+/-1.90%) and diabetic (Rmax: ACh = 64.09+/-5.14%, SNP = 95.84+/-1.41%) rats compared with aortic rings of normal rats (Rmax: ACh = 89%, SNP = 104.0+/-1.0%). The alpha1-receptor-mediated contractions induced by phenylephrine (PE) were augmented in diabetic (Cmax = 148.8+/-9.0%) rat aortic rings compared to both normal (Cmax = 127+/-6.9%) and SHR (Cmax = 118+/-4.5%) aortic rings. Ascorbic acid pretreatment was without any significant effects on the vascular responses to ACh, SNP and PE in aortic rings from normal rats. Ascorbic acid significantly improved ACh-induced relaxations in SHR (Rmax = 89.09+/-2.82%) aortic rings to a level similar to that observed in normal aortic rings, but this enhancement in ACh-induced relaxations was only partial in diabetic aortic rings. Ascorbic acid lacked any effects on SNP-induced relaxations in both SHR and diabetic aortic rings. Ascorbic acid markedly attenuated contractions induced by PE in aortic rings from both SHR (Cmax = 92.9+/-6.68%) and diabetic (Cmax = 116.9+/-9.4%) rats. Additionally, following inhibition of nitric oxide synthesis with l-NAME, ascorbic acid attenuated PE-induced contractions in all aortic ring types studied. These results suggest that (1) vascular hyper-responsiveness to alpha(1)-receptor agonists in diabetic arteries is independent of endothelial nitric oxide dysfunction; (2) ascorbic acid directly modulates contractile responses of hypertensive and diabetic rat aortas, likely through mechanisms in part independent of preservation of endothelium-derived nitric oxide.

Matched MeSH terms: Aorta, Thoracic/drug effects*
Des-aspartate angiotensin I (DAA-I) reduces endothelial dysfunction in the aorta of the spontaneously hypertensive rat through inhibition of angiotensin II-induced oxidative stress

Loh WM, Ling WC, Murugan DD, Lau YS, Achike FI, Vanhoutte PM, et al.

Vascul Pharmacol, 2015 Aug;71:151-8.
PMID: 25869508 DOI: 10.1016/j.vph.2015.03.011

Des-aspartate angiotensin I (DAA-I), an endogenous nonapeptide, counteracts several effects of angiotensin II on vascular tone. The aim of this study was to investigate the acute protective effect of DAA-I on endothelial function in the spontaneously hypertensive rat (SHR) as well as its effect on angiotensin II-induced contractions and oxidative stress. Aortic rings were incubated with DAA-I (0.1μM) for 30min prior to the assessment of angiotensin II-induced contractions (0.1nM-10μM) in WKY and SHR aortas. Total nitrate and nitrite levels were assessed using a colorimetric method and reactive oxygen species (ROS) were measured by dihydroethidium (DHE) fluorescence and lucigenin-enhanced chemiluminescence. The effect of DAA-I was also assessed against endothelium-dependent and -independent relaxations to acetylcholine and sodium nitroprusside, respectively. Angiotensin II-induced contractions were significantly reduced by DAA-I, losartan and tempol. Incubation with ODQ (soluble guanylyl cyclase inhibitor) and removal of the endothelium prevented the reduction of angiotensin II-induced contractions by DAA-I. Total nitrate and nitrite levels were increased in DAA-I, losartan and tempol treated-SHR tissues while ROS level was reduced by DAA-I and the latter inhibitors. In addition, DAA-I significantly improved the impaired acetylcholine-induced relaxation in SHR aortas whilst sodium nitroprusside-induced endothelium-independent relaxation remained unaffected. The present findings indicate that improvement of endothelial function by DAA-I in the SHR aorta is mediated through endothelium-dependent release of nitric oxide and inhibition of angiotensin II-induced oxidative stress.

Matched MeSH terms: Aorta, Thoracic/drug effects
Mechanisms underlining gender differences in Phenylephrine contraction of normoglycaemic and short-term Streptozotocin-induced diabetic WKY rat aorta

Aloysius UI, Achike FI, Mustafa MR

Vascul Pharmacol, 2012 Sep-Oct;57(2-4):81-90.
PMID: 22172524 DOI: 10.1016/j.vph.2011.11.009

The female gender reduces the risk, but succumbs more to cardiovascular disease. The hypothesis that short-term (8weeks) Streptozotocin-induced diabetes could produce greater female than male vascular tissue reactivity and the mechanistic basis were explored. Aortic ring responses to Phenylephrine were examined in age- and sex-matched normoglycaemic/diabetic rats. The normoglycaemic male tissue contracted significantly more than the normoglycaemic female and the male/female diabetic tissues. Endothelial-denudation, l-NAME or MB reversed these differences suggesting an EDNO-cGMP dependence. 17β-oestradiol exerted relaxant effect on all endothelium-denuded (and normoglycaemic endothelium-intact male) tissues, but not endothelium-intact normoglycaemic female. The greater male tissue contraction is attributable to absent 17β-oestradiol-modulated relaxation. Indomethacin blockade of COX attenuated male normoglycaemic and female diabetic tissue contraction (both reversed by l-NAME), but augmented diabetic male tissue contraction. These data are consistent with the raised contractile TXA(2) and PGE(2) in normoglycaemic male and diabetic female tissues, and the relaxant PGI(2) in diabetic male (and female). The higher levels of PGI(2) in the normoglycaemic and diabetic female perhaps explain their greater relaxant response to Acetylcholine compared to the respective male. In conclusion, there is an endothelium-dependent gender difference in the effect of short term diabetes on vascular tissue reactivity which is COX mediated.

Matched MeSH terms: Aorta, Thoracic/drug effects*
Fulltext Association of elevated blood pressure and impaired vasorelaxation in experimental Sprague-Dawley rats fed with heated vegetable oil

Leong XF, Mustafa MR, Das S, Jaarin K

Lipids Health Dis, 2010;9:66.
PMID: 20573259 DOI: 10.1186/1476-511X-9-66

Poor control of blood pressure leads to hypertension which is a major risk factor for development of cardiovascular disease. The present study aimed to explore possible mechanisms of elevation in blood pressure following consumption of heated vegetable oil.

Matched MeSH terms: Aorta, Thoracic/drug effects
Pharmacological mechanisms underlying the vascular activities of Loranthus ferrugineus Roxb. in rat thoracic aorta

Ameer OZ, Salman IM, Siddiqui MJ, Yam MF, Sriramaneni RN, Mohamed AJ, et al.

J Ethnopharmacol, 2010 Jan 8;127(1):19-25.
PMID: 19808083 DOI: 10.1016/j.jep.2009.09.057

The present study was aimed to investigate the pharmacological basis for the use of Loranthus ferrugineus in hypertension.

Matched MeSH terms: Aorta, Thoracic/drug effects*
Effect of alpha lipoic acid on oxidative stress and vascular wall of diabetic rats

Balkis Budin S, Othman F, Louis SR, Abu Bakar M, Radzi M, Osman K, et al.

Rom J Morphol Embryol, 2009;50(1):23-30.
PMID: 19221642

PREMISES AND OBJECTIVES: Antioxidant plays an important role in preventing the progression of diabetes mellitus (DM) complications. The aim of the present study was to investigate the effect of alpha lipoic acid (ALA) supplementation on plasma lipid, oxidative stress and vascular changes in diabetic rats.

Matched MeSH terms: Aorta, Thoracic/drug effects
Mechanisms underlying the antihypertensive effect of Alstonia scholaris

Bello I, Usman NS, Mahmud R, Asmawi MZ

J Ethnopharmacol, 2015 Dec 4;175:422-31.
PMID: 26429073 DOI: 10.1016/j.jep.2015.09.031

Alstonia scholaris has a long history of use in the Ayurveda traditional treatment of various ailments including hypertension. We have reported the blood pressure lowering activity of the extract of A. scholaris. The following research aim to delineate the pharmacological mechanism involve in the antihypertensive action.

Matched MeSH terms: Aorta, Thoracic/drug effects
Effects of flavonoids on vascular smooth muscle of the isolated rat thoracic aorta

Ajay M, Gilani AU, Mustafa MR

Life Sci, 2003 Dec 19;74(5):603-12.
PMID: 14623031

The potency, structure-activity relationship, and mechanism of vasorelaxation of a series of flavonoids, representing different subclasses (flavonols: fisetin, rutin, quercetin; flavones: chrysin, flavone, baicalein; flavanones: naringenin, naringin; isoflavones: diadzein and flavanes: epigallo catechin gallate), were examined in the isolated rat aorta. Most of the flavonoids tested showed concentration dependent relaxant effects against K+ (80 mM) and phenylephrine (PE, 0.1 microM)-induced contractions with a greater inhibition of the responses to the alpha1-adrenoceptor agonist. The relaxant effects of most of the flavonoids involve in part the release of nitric oxide and prostaglandins from the endothelium as pretreatment with L-NAME and indomethacin attenuated the responses. In addition, the relaxant action of the flavonoids includes inhibition of Ca+2 influx and release of Ca+2 from intracellular stores. A structure-activity relationship amongst the flavonoids was suggested.

Matched MeSH terms: Aorta, Thoracic/drug effects*
Fulltext Clinacanthus nutans Leaves Extract Reverts Endothelial Dysfunction in Type 2 Diabetes Rats by Improving Protein Expression of eNOS

Azemi AK, Mokhtar SS, Rasool AHG

Oxid Med Cell Longev, 2020;2020:7572892.
PMID: 32879653 DOI: 10.1155/2020/7572892

Diabetes mellitus is associated with endothelial dysfunction; it causes progressive vascular damage resulting from an impaired endothelium-dependent vasorelaxation. In the diabetes state, presence of hyperglycemia and insulin resistance predisposes to endothelial dysfunction. Clinacanthus nutans, widely used as a traditional medicine for diabetes is reported to have hypoglycemic, hypolipidemic, antioxidant, and anti-inflammatory properties. However, the possibility of C. nutans affecting the vascular endothelial function in diabetes remains unclear. This study was aimed at evaluating the effects of C. nutans methanolic leaves extract (CNME) on endothelial function in a type 2 diabetes (T2DM) rat model. Sixty male Sprague-Dawley rats were divided into five groups (n = 12 per group): nondiabetic control, nondiabetic treated with four weeks of CNME (500 mg/kg/daily), untreated diabetic rats, diabetic treated with metformin (300 mg/kg/daily), and diabetic treated with CNME (500 mg/kg/daily). T2DM was induced by a single intraperitoneal injection of low-dose streptozotocin (STZ) to rats fed with high-fat diet (HFD). Endothelial-dependent and endothelial-independent relaxations and contractions of the thoracic aorta were determined using the organ bath. Aortic endothelial nitric oxide synthase (eNOS) expression was determined using Western blotting. Endothelial-dependent relaxation was reduced in diabetic rats. Both diabetic groups treated with CNME or metformin significantly improved the impairment in endothelium-dependent vasorelaxation; this was associated with increased expression of aortic eNOS protein. CNME- and metformin-treated groups also reduced aortic endothelium-dependent and aortic endothelium-independent contractions in diabetics. Both of these diabetic-treated groups also reduced blood glucose levels and increased body weight compared to the untreated diabetic group. In conclusion, C. nutans improves endothelial-dependent vasodilatation and reduces endothelial-dependent contraction, thus ameliorating endothelial dysfunction in diabetic rats. This may occur due to its effect on increasing eNOS protein expression.

Matched MeSH terms: Aorta, Thoracic/drug effects
Gynura procumbens causes vasodilation by inhibiting angiotensin II and enhancing bradykinin actions

Poh TF, Ng HK, Hoe SZ, Lam SK

J Cardiovasc Pharmacol, 2013 May;61(5):378-84.
PMID: 23328388 DOI: 10.1097/FJC.0b013e31828685b3

Previous studies showed that Gynura procumbens reduced blood pressure by blocking calcium channels and inhibiting the angiotensin-converting enzyme activity. The present experiments were to further explore the effects and mechanisms of a purer aqueous fraction (FA-I) of G. procumbens on angiotensin I (Ang I)-induced and angiotensin II (Ang II)-induced contraction of aortic rings and also on the bradykinin (BK) effect on cardiovascular system. Rat aortic rings suspended in organ chambers were used to investigate the vascular reactivity of FA-I. Effect of FA-I on BK was studied by in vitro and in vivo methods. Results show that FA-I significantly (P < 0.05) decreased the contraction evoked by Ang I and Ang II. In the presence of indomethacin (10 µM) or N-nitro-L-arginine methyl ester (0.1 µM), the inhibitory effect of FA-I on Ang II-induced contraction of aortic rings was reduced. Besides, FA-I potentiated the vasorelaxant effect and enhanced the blood pressure-lowering effect of BK. In conclusion, FA-I reduced the contraction evoked by Ang II probably via the endothelium-dependent pathways, which involve activation of the release of nitric oxide and prostaglandins. The inhibition of angiotensin-converting enzyme activity by FA-I may contribute to the potentiation of the effects of BK on cardiovascular system.

Matched MeSH terms: Aorta, Thoracic/drug effects
Blood pressure lowering effect and vascular activity of Phyllanthus niruri extract: The role of NO/cGMP signaling pathway and β-adrenoceptor mediated relaxation of isolated aortic rings

Bello I, Usman NS, Dewa A, Abubakar K, Aminu N, Asmawi MZ, et al.

J Ethnopharmacol, 2020 Mar 25;250:112461.
PMID: 31830549 DOI: 10.1016/j.jep.2019.112461

ETHNOPHARMACOLOGICAL RELEVANCE: Phyllanthus niruri have a long history of use in the traditional treatment of various ailments including hypertension. Literature reports have indicated that it is a potent antihypertensive herbal medication used traditionally.
AIM OF THE STUDY: This study was carried out to investigate the antihypertensive and vasodilatory activity of four solvents extracts of P. niruri namely; petroleum ether (PEPN), chloroform (CLPN), methanol (MEPN) and water (WEPN), with the aim of elucidating the mechanism of action and identifying the phytochemical constituents.
MATERIALS AND METHODS: Male Spontaneous Hypertensive Rats (SHRs) were given oral gavage of P. niruri extract daily for two weeks and the blood pressure was recorded in vivo. We also determine the vasodilation effect of the extracts on rings of isolated thoracic aorta pre-contracted with phenylephrine (PE, 1 μM). Endothelium-intact or endothelium-denuded aorta rings were pre-incubated with various antagonists like 1H-[1,2,4] oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ, 10 μM) and Methylene blue (MB 10 μM), sGC inhibitors; Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME, 10 μM) a nitric oxide synthase (NOS) inhibitor; atropine (10 μM), a cholinergic receptor blocker; indomethacin (10 μM), a cyclooxygenase inhibitor and various K+ channel blockers such as glibenclamide (10 μM) and tetraethyl ammonium (TEA 10 μM) for mechanism study.
RESULTS: SHRs receiving P. niruri extracts showed a significant decrease in their blood pressure (BP) when compared to the baseline value, with PEPN being more potent. The extracts (0.125-4 mg/mL) also induced vasorelaxation on endothelium-intact aorta rings. PEPN elicited the most potent maximum relaxation effect (Rmax). Mechanism assessment of PEPN showed that its relaxation effect is significantly suppressed in endothelium-denuded aorta rings. Pre-incubation of aorta rings with atropine, L-NAME, ODQ, indomethacin, and propranolol also significantly attenuated its relaxation effect. Conversely, incubation with TEA and glibenclamide did not show a significant effect on PEPN-induced relaxation.
CONCLUSION: This study indicates that the antihypertensive activity of P. niruri extract is mediated by vasoactive phytoconstituents that dilate the arterial wall via endothelium-dependent pathways and β-adrenoceptor activity which, in turn, cause vasorelaxation and reduce blood pressure.

Matched MeSH terms: Aorta, Thoracic/drug effects
Vasorelaxant Action of the Chloroform Fraction of Orthosiphon stamineus via NO/cGMP Pathway, Potassium and Calcium Channels

Yam MF, Tan CS, Ahmad M, Ruan S

Am J Chin Med, 2016;44(7):1413-1439.
PMID: 27785939

Orthosiphon stamineus Benth. (Lamiaceae) is an important plant in traditional folk medicine that is used to treat hypertension and kidney stones. In humans, this plant has been tested as an addition regiment for antihypertensive treatment. Among the treatments for hypertension, O. stamineus had been to have diuretic and vasorelaxant effects in animal models. There is still very little information regarding the vasorelaxant effect of O. stamineus. Therefore, the present study was designed to investigate the vasorelaxant activity and mechanism of action of the fractions of O. stamineus. The vasorelaxant activity and the underlying mechanisms of the chloroform fraction of the 50% methanolic extract of O. stamineus (CF) was evaluated on thoracic aortic rings isolated from Sprague Dawley rats. CF caused relaxation of the aortic ring pre-contracted with phenylephrine in the presence and absence of endothelium, and pre-contracted with potassium chloride in endothelium-intact aortic ring. In the presence of endothelium, both indomethacin (a nonselective cyclooxygenase inhibitor) and [Formula: see text]-[1,2,4]Oxadiazolo[4,3-[Formula: see text]]quinoxalin-1-one (ODQ, selective soluble guanylate cyclase inhibitor) had a small effect on the vasorelaxation response. On the other hand, in the presence of Nω-nitro-L-arginine methyl ester (L-NAME, nitric oxide synthase inhibitor), methylene blue (cyclic guanosine monophosphate lowering agent), tetraethylammonium ([Formula: see text], nonselective calcium activator [Formula: see text] channel blocker), 4-aminopyridine (4-AP, voltage-dependent [Formula: see text] channel blocker), barium chloride ([Formula: see text], inwardly rectifying [Formula: see text] channel blocker), glibenclamide (nonspecific ATP-sensitive [Formula: see text] channel blocker), atropine (muscarinic receptor blocker) and propranolol (β-adrenergic receptor blocker), the vasorelaxant effect significantly reduced the relaxation stimulated by CF. CF was also found to be active in reducing [Formula: see text] release from the sarcoplasmic reticulum and blocking calcium channels.

Matched MeSH terms: Aorta, Thoracic/drug effects
Changes in blood pressure, vascular reactivity and inflammatory biomarkers following consumption of heated corn oil

Das S, Hamsi MA, Kamisah Y, Qodriyah HMS, Othman F, Emran A, et al.

Pak J Pharm Sci, 2017 Sep;30(5):1609-1615.
PMID: 29084680

Consumption of corn oil for cooking purpose is gaining popularity. The present study examined the effect of heated corn oil on blood pressure and its possible mechanism in experimental rats. Thirty male Sprague-Dawley rats were randomly divided into 5 groups and were fed with the following diets, Group I was fed with basal diet only; whereas group II,III,IV and V were fed with basal diet fortified with 15% (w/w) either fresh, once-heated, five-times-heated or ten-times-heated corn oil, respectively for 16 weeks. Body weight, blood pressure were measured at baseline and weekly interval for 16 weeks. Inflammatory biomarkers which included soluble intracellular adhesion molecules (sICAM), soluble vascular adhesion molecules (sVCAM) and C reactive protein (CRP), were measured at baseline and the end of 16 weeks. The rats were sacrificed and thoracic aorta was taken for measurement of vascular reactivity. There was significant increase in the blood pressure in the groups fed with heated once, five-times (5HCO) and ten-times-heated corn oil (10-HCO) compared to the control. The increase in the blood pressure was associated with an increase in CRP, sICAM and sVCAM, reduction in vasodilatation response to acetylcholine and greater vasoconstriction response to phenylephrine. The results suggest that repeatedly heated corn oil causes elevation in blood pressure, vascular inflammation which impairs vascular reactivity thereby predisposing to hypertension. There is a need to educate people not to consume corn oil in a heated state.

Matched MeSH terms: Aorta, Thoracic/drug effects*

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