HUMAN CHORIONIC-GONADOTROPIN DIRECTLY AND INDIRECTLY ALTERS UTERINE ARTERIOLAR DIAMETERS IN CYCLING RATS

OBJECTIVE: Our purpose was to investigate whether uterine microvascula r responses to human chorionic gonadotropin application depend on rout e of administration and estrous cycle day. STUDY DESIGN: One uterine h orn was exteriorized in pentobarbital-anesthetized cycling and ovariec tomized rats and superfused with Krebs solution. Uterine arterioles (6 4 +/- 2.1 mu m) were viewed by videomicroscopy. Diameters were measure d during a 20-minute baseline period and for 60 minutes during human c horionic gonadotropin suffusion (20 IU/60 ml) or 60 minutes after intr aperitoneal injection of 50 IU of human chorionic gonadotropin. Papave rine (100 mu mol/L) suffusion maximally dilated the uterine arterioles (80 +/- 2.6 mu m). RESULTS: 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 gonadot ropin resulted in arteriolar constriction on diestrus-2 (76% +/- 5% ba seline) and proestrus (82% +/- 3% baseline). Ovariectomy eliminated th e effects of injected but not suffused human chorionic gonadotropin. A ll results are significant at p < 0.05. CONCLUSIONS: Results indicate estrous cycle day-dependent direct and indirect effects of human chori onic gonadotropin on the resistance of uterine arterioles.