The effect of kininase II inhibitors on the response of feline cerebral arteries to bradykinin and angiotensin.

Bradykinin (BK) produced concentration-related relaxations of cat middle cerebral arteries and was ineffective on cat basilar arteries in vitro under resting tension and when contracted with 5-hydroxy-tryptamine (5-HT). Angiotensin I and II (AI, AII) produced concentration-related contraction on both arteries, AII being approximately 10 times more potent than AI. The angiotensin-converting-enzyme inhibitors, SQ, 14225, BPP5a and BPP9a had no effect on the concentration effect curves to BK, AII or 5-HT but responses to AI were inhibited. These results suggest that angiotensin-converting-enzyme is present in both preparations and is important for the conversion of AI to AII but apparently not for the degradation of BK.