Human chorionic gonadotropin directly and indirectly alters uterine arteriolar diameters in cycling rats.

<bold>Objective: </bold>Our purpose was to investigate whether uterine microvascular responses to human chorionic gonadotropin application depend on route of administration and estrous cycle day.<bold>Study Design: </bold>One uterine horn was exteriorized in pentobarbital-anesthetized cycling and ovariectomized rats and superfused with Krebs solution Uterine arterioles (64 +/- 2.1 microns) were viewed by videomicroscopy. Diameters were measured during a 20-minute baseline period and for 60 minutes during human chorionic gonadotropin suffusion (20 IU/60 ml) or 60 minutes after intraperitoneal injection of 50 IU of human chorionic gonadotropin. Papaverine (100 mumol/L) suffusion maximally dilated the uterine arterioles (80 +/- 2.6 microns).<bold>Results: </bold>Suffusion of human chorionic gonadotropin-dilated arterioles on diestrus-1 (122% +/- 2% baseline) and diestrus-2 (118% +/- 4% baseline) but constricted arterioles on proestrus (78% +/- 7% baseline). Intraperitoneal injection of human chorionic gonadotropin resulted in arteriolar constriction on diestrus-2 (76% +/- 5% baseline) and proestrus (82% +/- 3% baseline). Ovariectomy eliminated the effects of injected but not suffused human chorionic gonadotropin. All results are significant at p < 0.05.<bold>Conclusions: </bold>Results indicate estrous cycle day-dependent direct and indirect effects of human chorionic gonadotropin on the resistance of uterine arterioles. [ABSTRACT FROM AUTHOR]