ROLES OF NO-SYNTHASE AND CYCLOOXYGENASE IN SEX-DEPENDENT AND PREGNANCY-DEPENDENT ARTERIAL AND VENOUS PRESSURES IN THE RAT

The roles of NO synthase (NOS) and cyclooxygenase on vascular pressure s were studied as a function of sex and pregnancy. After anesthesia, m ean arterial pressure (MAP) and mean circulatory filling pressure were lower in pregnant rats compared with male and virgin rats, but N-G-ni tro-L-arginine methyl ester (L-NAME; 30 mg/kg) induced similar increas es in MAP. Pithing abolished these pressure differences, suggesting a diminished autonomic reflex in pregnancy, and led in pregnant rats to a lower arterial and venous NO modulation. In separately perfused mese nteries, the lower responses to KCI observed in venous beds of female compared with male rats do not involve any dysfunction of NOS activity in the mesenteries isolated from virgin and pregnant rats. The cycloo xygenase path way is implicated in the KCl-induced responses of vessel s taken from male rats and of venous mesentery from pregnant rats. Hut prostanoids do not share in the acetylcholine (ACh)-induced relaxatio ns in the arterial and venous K+-contracted mesenteric vasculatures is olated from any of the groups of rats.