Water deprivation (WD) induces changes in plasma volume and osmolality, which in turn activate several responses, including thirst, the activation of the renin-angiotensin system (RAS) and vasopressin (AVP) and oxytocin (OT) secretion. These systems seem to be influenced by oestradiol, as evidenced by the expression of its receptor in brain areas that control fluid balance. Thus, we investigated the effects of oestradiol treatment on behavioural and neuroendocrine changes of ovariectomized rats in response to WD. We observed that in response to WD, oestradiol treatment attenuated water intake, plasma osmolality and haematocrit but did not change urinary volume or osmolality. Moreover, oestradiol potentiated WD-induced AVP secretion, but did not alter the plasma OT or angiotensin II (Ang II) concentrations. Immunohistochemical data showed that oestradiol potentiated vasopressinergic neuronal activation in the lateral magnocellular PVN (PaLM) and supraoptic (SON) nuclei but did not induce further changes in Fos expression in the median preoptic nucleus (MnPO) or subfornical organ (SFO) or in oxytocinergic neuronal activation in the SON and PVN of WD rats. Regarding mRNA expression, oestradiol increased OT mRNA expression in the SON and PVN under basal conditions and after WD, but did not induce additional changes in the mRNA expression for AVP in the SON or PVN. It also did not affect the mRNA expression of RAS components in the PVN. In conclusion, our results show that oestradiol acts mainly on the vasopressinergic system in response to WD, potentiating vasopressinergic neuronal activation and AVP secretion without altering AVP mRNA expression.
Human risk allele carriers of Lysine-Specific Demethylase 1 (LSD1) and LSD1 deficient mice have salt sensitive hypertension for unclear reasons. We hypothesized that LSD1 deficiency causes dysregulation of aldosterone's response to salt intake resulting in increased cardiovascular risk factors [blood pressure and microalbumin]. Furthermore, we determined the effect of biological sex on these potential abnormalities. To test our hypotheses, LSD1 male and female heterozygote knockout (LSD1+/-) and wild type (WT) mice were assigned to two age groups: 18 weeks and 36 weeks. Plasma aldosterone levels and aldosterone production from zona glomerulosa cells studied ex vivo were greater in both male and female LSD1+/- mice consuming a liberal salt diet as compared to WT mice consuming the same diet. However, salt sensitive blood pressure elevation and increased microalbuminuria were only observed in male LSD1+/- mice. These data suggest that LSD1 interacts with aldosterone's secretory response to salt intake. Lack of LSD1 causes inappropriate aldosterone production on a liberal salt diet; males appear to be more sensitive to this aldosterone increase as males, but not females, develop salt sensitivity of blood pressure and increased microalbuminuria. The mechanism responsible for the cardiovascular protective effect in females is uncertain but may be related to estrogen modulating the effect of mineralocorticoid receptor activation.
The effects of exogenously introduced oestradiol-17 beta (E) and relaxin (RLX) on cervical extensibility and collagen organisation were tested in rats ovariectomised in late pregnancy. When the cervices were stretched in vitro by 1 mm increments, it was found that those from rats given E alone generated significantly higher tensions than those from control rats, while cervices from rats given both E and RLX had tensions similar to controls. Examination of cervical sections under the light microscope and ultra-thin sections under the electron microscope showed that the collagen fibres in the cervices from E-treated rats were highly organised, whereas those from animals given E+RLX and control animals were disorganised and dispersed. It was concluded that E decreased cervical extensibility, while RLX counteracted the effect of E to maintain a soft and easily extensible cervix.
The possible role of cyclic adenosine 3',5'-monophosphate (cAMP) in mediating the action of steroid hormones was investigated using the rat lung. Male rats were adrenalectomized and treated with olive oil, dexamethasone, corticosterone, deoxycorticosterone (DOC) or progesterone. At the end of 10 days, 100 micrograms isoprenaline/kg was injected intraperitoneally 5 min before the animals were killed to stimulate cAMP production. Adrenalectomy significantly decreased cAMP levels in the rat lung. Dexamethasone and corticosterone pretreatment reversed the effect of adrenalectomy whereas progesterone pretreatment but not DOC pretreatment significantly decreased lung cAMP levels. Cyclic AMP levels in normal female rats, whether pregnant or not, were not significantly different from those in male rats. We concluded that the absence of glucocorticoid, as after adrenalectomy, decreased the cAMP levels in rat lungs and that this could be reversed by either dexamethasone or corticosterone replacement. Progesterone reduced the cAMP content in rat lungs by acting as a glucocorticoid antagonist or by acting directly via progesterone receptors.
Inconsistencies have been reported on the effect of sex on aldosterone (ALDO) levels leading to clinical confusion. The reasons for these inconsistencies are uncertain but include estrogen and/or its receptor modulating target gene responses to mineralocorticoid receptor activation and ALDO secretagogues' levels. This study's goal was to determine whether ALDO's biosynthesis also differed by sex. Two approaches were used. First, plasma renin activity and aldosterone were measured in rats. Both were significantly higher in males. Secondly, using rat zona glomerulosa (ZG) cells, we assessed three ex vivo areas: (1) activity/levels of early steps in ALDO's biosynthesis (StAR and CYP11A1); (2) activity/levels of a late step (CYP11B2); and (3) the status of the mineralocorticoid receptor (MR)-mediated, ultrashort feedback loop. Females had higher expression of CYP11A1 and StAR and increased CYP11A1 activity (increased pregnenolone/corticosterone levels) but did not differ in CYP11B2 expression or activity (ALDO levels). Activating the ZG's MR (thereby activating the ultrashort feedback loop) reduced CYP11B2's activity similarly in both sexes. Exvivo, these molecular effects were accompanied, in females, by lower ALDO basally but higher ALDO with angiotensin II stimulation. In conclusion, we documented that not only was there a sex-mediated difference in the activity of ALDO's biosynthesis but also these differences at the molecular level help explain the variable reports on ALDO's circulating levels. Basally, both in vivo and ex vivo, males had higher ALDO levels, likely secondary to higher ALDO secretagogue levels. However, in response to acute stimulation, ALDO levels are higher in females because of the greater levels and/or activity of their StAR/CYP11A1.
Biologic sex influences the development of cardiovascular disease and modifies aldosterone (ALDO) and blood pressure (BP) phenotypes: females secrete more ALDO, and their adrenal glomerulosa cell is more sensitive to stimulation. Lysine-specific demethylase 1 (LSD1) variants in Africans and LSD1 deficiency in mice are associated with BP and/or ALDO phenotypes. This study, in 18- and 40-week-old wild type (WT) and LSD1+/- mice, was designed to determine whether (1) sex modifies ALDO biosynthetic enzymes; (2) LSD1 deficiency disrupts the effect of sex on these enzymes; (3) within each genotype, there is a positive relationship between ALDO biosynthesis (proximate phenotype), plasma ALDO (intermediate phenotype) and BP levels (distant phenotype); and (4) sex and LSD1 genotype interact on these phenotypes. In WT mice, female sex increases the expression of early enzymes in ALDO biosynthesis but not ALDO levels or systolic blood pressure (SBP). However, enzyme expressions are shifted downward in LSD1+/- females vs males, so that early enzyme levels are similar but the late enzymes are substantially lower. In both age groups, LSD1 deficiency modifies the adrenal enzyme expressions, circulating ALDO levels, and SBP in a sex-specific manner. Finally, significant sex/LSD1 genotype interactions modulate the three phenotypes in mice. In conclusion, biologic sex in mice interacts with LSD1 deficiency to modify several phenotypes: (1) proximal (ALDO biosynthetic enzymes); (2) intermediate (circulating ALDO); and (3) distant (SBP). These results provide entry to better understand the roles of biological sex and LSD1 in (1) hypertension heterogeneity and (2) providing more personalized treatment.