Increased sensitivity to bradykinin in pregnant rats.

We tested the effects of late pregnancy on the depressor response to bradykinin (100, 200 and 400ng) in rats. All experiments were performed under anesthesia by intraperitoneal injection of pentobarbital (50 mg/kg). Catheters were connected to the arterial and venous lines for blood pressure recording and administration of drugs. Late pregnancy (19- to 21-day) showed a hypersensitivity of the depressor response to bradykinin. The effects of captopril, Kininase II inhibitor, on the depressor response to bradykinin were examined in rats. Since captopril (50, 100 and 200 micrograms) notably increased the depressor response to bradykinin both in nonpregnant and 19- to 21-day pregnant rats, kininase II acts as a bradykinin metabolizing enzyme in vivo. Captopril (50, 100, 200 micrograms), however, resulted in the augmented parallel increases of depressor response to bradykinin (100ng) in both nonpregnant and pregnant rats. Our data may suggest that kininase II is not involved in the hypersensitivity to bradykinin in late pregnancy in rats.