Human chorionic gonadotropin attenuates the vascular response to angiotensin II.

Objective: Our purpose was to investigate interactions between human chorionic gonadotropin (hCG) and angiotensin II (ANG II) in resistance arteries.

Study Design: Isolated pre-arteriolar vessels of female Sprague-Dawley rats were prepared from the mesenteric arcade and the mesometrium. Dose-response curves were recorded by means of an video-electronic arteriograph system.

Results: (1) hCG dilated mesenteric (MA; EC(50): 21+/-6.9 mU/ml) and uterine (UA; EC(50): 256+/-44.3 mU/ml)) resistance arteries pre-constricted with ANG II. In the presence of glybenclamide (1 micromol/l), the response of MA was reduced by >50%. (2) After application of hCG for 1h, vasoconstriction by ANG II was significantly attenuated in MA. This effect was dose-dependent and was not observed in UA. Efficacy of ANG II could be restored, when hCG was followed by glybenclamide.

Conclusions: hCG may contribute to the reduction in arterial tone seen early in human pregnancy. Its vascular effects are in part mediated by the activation of adenosine 5'-triphosphate-sensitive potassium channels, suggesting a protein kinase A dependent signaling pathway.