Gonadectomy potentiated the responsiveness of the afferent arteriole to ETB-induced vasoconstriction in female rats, but not males, while ET-1 responses were unchanged by sex or gonadectomy.
Gonadectomy potentiated the responsiveness of the afferent arteriole to ET B-induced vasoconstriction in female but not male rats, suggesting female sex hormones influence ET B-mediated vasoconstriction in the renal microcirculation.
The pathogenesis of hypertension is distinct between men and women. Endothelin-1 (ET-1) is a potential contributor to sex differences in the pathophysiology of hypertension. ET-1 participates in blood pressure regulation through activation of endothelin A (ET A ) and endothelin B (ET B ) receptors including those in the vasculature. Previous studies demonstrated that sex and sex hormones evoke discrepancies in ET-1-mediated control of vascular tone in different vascular beds. However, little is known about sex- and sex hormone-related differences in ET-1-dependent renal microvascular reactivity. Accordingly, we hypothesized that loss of sex hormones impairs afferent arteriole reactivity to ET-1. Male and female Sprague Dawley rats were subjected to gonadectomy or sham surgery ( n = 6/group). After 3 weeks, kidneys from those rats were prepared for assessment of renal microvascular responses to ET-1 (ET A and ET B agonist, 10 −12 to 10 −8 M) and sarafotoxin 6c (S6c, ET B agonist, 10 −12 to 10 −8 M) using the blood-perfused juxtamedullary nephron preparation. Control afferent arteriole diameters at 100 mmHg were similar between sham male and female rats averaging 14.6 ± 0.3 and 15.3 ± 0.3 μm, respectively. Gonadectomy had no significant effect on control arteriole diameter. In sham males, ET-1 produced significant concentration-dependent decreases in afferent arteriole diameter, with 10 −8 M ET-1 decreasing diameter by 84 ± 1%. ET-1 induced similar concentration-dependent vasoconstrictor responses in sham female rats, with 10 −8 M ET-1 decreasing the diameter by 82 ± 1%. The afferent arteriolar vasoconstrictor responses to ET-1 were unchanged by ovariectomy or orchiectomy. Selective ET B receptor activation by S6c induced a concentration-dependent decline in afferent arteriole diameter, with 10 −8 M S6c decreasing diameter by 77 ± 3 and 76 ± 3% in sham male and female rats, respectively. Notably, ovariectomy augmented the vasoconstrictor response to S6c (10 −12 to 10 −9 M), whereas orchiectomy had no significant impact on the responsiveness to ET B receptor activation. These data demonstrate that sex does not significantly influence afferent arteriole reactivity to ET receptor activation. Gonadectomy potentiated the responsiveness of the afferent arteriole to ET B -induced vasoconstriction in females, but not males, suggesting that female sex hormones influence ET B -mediated vasoconstriction in the renal microcirculation.
Gohar et al. (Thu,) conducted a other in Hypertension / Renal microvascular reactivity (n=24). Gonadectomy (ovariectomy or orchiectomy) vs. Sham surgery was evaluated on Afferent arteriole diameter response to ET-1 and S6c. Gonadectomy potentiated the responsiveness of the afferent arteriole to ETB-induced vasoconstriction in female rats, but not males, while ET-1 responses were unchanged by sex or gonadectomy.