M. Ezimokhai et al., Human chorionic gonadotrophin is an endothelium-independent inhibitor of rat aortic smooth muscle contractility, AM J HYPERT, 13(1), 2000, pp. 66-73
The study tested the hypothesis that human chorionic gonadotrophin (hCG) at
tenuates isolated vascular smooth muscle contractility and investigated the
role of the vascular endothelium in hCG-induced altered responses of vascu
lar smooth muscle. The contractile responses of isolated aortic rings from
normal, hCG-treated, and estrogen-treated female virgin Wistar rats to phen
ylephrine, angiotensin II, KCl, and CaCl2 were compared. The effect of pret
reatment with N-monomethyl-L-arginine (L-NMMA), methylene blue, indomethaci
n, calcium-free medium, and deendothelialization on responses to phenylephr
ine of aortic rings from control and hCG-treated rats were also examined. I
ntraperitoneal administration of hCG caused attenuation of contractile resp
onses of isolated aortic rings to all agents. The attenuated responses to p
henylephrine were not reversed by de-endothelialization, or pretreatment of
the rings with L-NMMA, methylene blue, or indomethacin. It was concluded t
hat hCG attenuates vascular smooth muscle contractility. The effect is inde
pendent of the vascular endothelium, not agonist-specific, and appears to i
nvolve alterations of calcium availability. (C) 2000 American Journal of Hy
pertension, Ltd.