The functional responses of different overnight-stored in vitro tissues are not clearly described in any animal model. The influence of overnight storage in an animal model may vary between tissue types. We employed Sprague-Dawley rat as our animal model and investigated the functional changes of rat aorta, trachea, bronchus and bladder that were used (i) immediately after surgical removal (denoted as fresh) and (ii) after storage in aerated (95% O2, 5% CO2) Krebs-Ringer bicarbonate solution at 4 °C for 24 h (denoted as stored). The aorta ring was pre-contracted with phenylephrine, and the functional response of the tissue was investigated using isoprenaline, forskolin and carbachol. Carbachol was also used to increase the tone in trachea, bronchus rings and bladder strips. A clear reduced function of endothelium, with a minor if any effect in the smooth muscle function in rat aorta was observed after overnight storage. The contractile response of overnight-stored rat airway (trachea and bronchus) and bladder smooth muscles remained unchanged. Among all tested tissues, only bronchus showed a reduced response rate (only 40% responded) after storage. In vitro rat tissues that are stored in Krebs solution at 4 °C for 24 h can still be used to investigate smooth muscle responses, however, not endothelium-mediated responses for aorta. The influence of overnight storage on different tissues from an animal model (Sprague-Dawley rat in our study) also provides an insight in maximising the use of sacrificed animals.
The general notion of activation of Gq-protein coupled receptors (GPCR) involves the mobilisation of stored and extracellular calcium and leads to smooth muscle tissue contraction. The aim of this study was to investigate the involvement of calcium mediated contractions in vascular and airway smooth muscles. Using standard organ bath procedures, aortic and tracheal rings were obtained from 6 to 8 week-old male Sprague Dawley rats. To activate the Gq protein receptors, phenylephrine (PE), an α1-adrenoceptor agonist, and carbachol, a M3 cholinoceptor agonist was added to baths containing the aortic and tracheal rings, respectively. The maximum response (Emax) to PE was reduced from 158.8 ± 11.8% (n=6) to 62.5 ± 12.4 % (n=8) upon removal of extracellular calcium in Krebs-Ringer solution. Maximal response to PE was also suppressed in the presence of nifedipine, a L-type Ca2+ channel inhibitor, (70.3 ± 11 %, n=8) and SKF96365, a canonical transient receptor potential cation channel inhibitor, (26.7 ± 13.2 %, n=5) when the influx of extracellular calcium was blocked. Removal of stored calcium also attenuated the PE contraction (p0.05). From these observations, we conclude that the role of stored and extracellular calcium in Gq protein activation is not the same across different types of smooth muscle tissues.
Myogenic tone is the response of the vascular smooth muscle to an increase in intraluminal pressure with vasoconstriction and with vasodilation when the pressure is decreased. Such myogenic tone contributes a level of physiological basal tone in response to neurohumoral stimuli. In spite of myogenic tone discovery by Sir William Bayliss 100 years ago, questions still remain regarding the underlying signaling mechanism of the myogenic response. Studies have shown that increased intraluminal pressure or wall tension leads to membrane depolarization, voltage-operated calcium channel (VOCC), stretch-activated cation (SAC) channels, extracelullar matrix (ECM) and actin cytoskeleton. Recently, evidence has shown a potential role for reactive oxygen species (ROS) as a key signalling mediator in the genesis of myogenic tone. The identification of the primary mechanosensors in the initiation of pressure-dependent myogenic tone is essential as these components could be potential therapeutical targets in the future.
A clinicohistological study of acute atherosis in molar pregnancy was undertaken. Maternal decidual vessels in currettage samples of 38 histologically confirmed complete hydatidiform moles were examined histologically for acute atherosis, recognised as fibrinoid necrosis of the smooth muscle wall with a perivascular mononuclear cell infiltrate, with or without lipophages. Acute atherosis was detected in eight of 38 cases, an incidence of 18.4%. All the patients were normotensive. The significance of acute atherosis in molar pregnancy remains to be clarified.
This paper is a review on the types of antagonists and the signaling mechanism pathways that have been used to determine the mechanisms of action employed for vasodilation by test compounds. Thus, we exhaustively reviewed and analyzed reports related to this topic published in PubMed between the years of 2010 till 2015. The aim of this paperis to suggest the most appropriate type of antagonists that correspond to receptors that would be involved during the mechanistic studies, as well as the latest signaling pathways trends that are being studied in order to determine the route(s) that atest compound employs for inducing vasodilation. The methods to perform the mechanism studies were included. Fundamentally, the affinity, specificity and selectivity of the antagonists to their receptors or enzymes were clearly elaborated as well as the solubility and reversibility. All the signaling pathways on the mechanisms of action involved in the vascular tone regulation have been well described in previous review articles. However, the most appropriate antagonists that should be utilized have never been suggested and elaborated before, hence the reason for this review.
The seeds of Swietenia macrophylla King (SM) (Meliaceae) are used as a folk medicine for the treatment of hypertension in Malaysia. However, the antihypertensive and vasorelaxant effects of SM seeds are still not widely studied. Thus, this study was designed to investigate the in vivo antihypertensive effects and in vitro mechanism of vasorelaxation of a 50% ethanolic SM seed extract (SM50) and the fingerprint of SM50 was developed through tri-step Fourier transform infrared (FTIR) spectroscopy. The vasorelaxant activity and the underlying mechanisms of SM50 were evaluated on thoracic aortic rings isolated from Sprague-Dawley rats in the presence of antagonists. The pharmacological effect of SM50 was investigated by oral administration of spontaneously hypertensive rats (SHRs) with three different doses of SM50 (1000, 500, and 250 mg/kg/day) for 4 weeks and their systolic blood pressure (SBP) and diastolic blood pressure (DBP) values were measured weekly using tail-cuff method. The tri-step FTIR macro-fingerprint of SM50 showed that SM50 contains stachyose, flavonoids, limonoids, and ester, which may contribute to its vasorelaxant effect. The results showed that the vasorelaxant activity of SM50 was mostly attributed to channel-linked receptors pathways through the blockage of voltage-operated calcium channels (VOCC). SM50 also acts as both potassium channels opener and inositol triphosphate receptor (IP3R) inhibitor, followed by β2-adrenergic pathway, and ultimately mediated through the nitric oxide/soluble guanylyl cyclase/cyclic 3',5'-guanosine monophosphate (NO/sGC/cGMP) signaling pathways. The treatment of SM50 also significantly decreased the SBP and DBP in SHRs. In conclusion, the antihypertensive mechanism of SM50 was mediated by VOCC, K+ channels, IP3R, G-protein-coupled β2-adrenergic receptor, and followed by NO/sGC/cGMP signaling mechanism pathways in descending order. The data suggested that SM50 has the potential to be used as a herbal medicament to treat hypertension.