Vasoconstrictive effects of angiotensin I and II in cat femoral arteries. Role of endothelium.

1. AI and AII induced concentration-dependent contractions in cat femoral artery segments, the potency of AII being greater than that of AI. 2. The antagonist of AII receptors, saralasin (1 and 10 nM), inhibited the AI and AII responses. 3. Indomethacin (10 microM) and endothelium removal increased the responses to AII, whereas those induced by AI were barely affected. 4. The response induced by AI was reduced by captopril (200 microM). 5. These data suggest: (1) the contractions induced by AII are mediated by AII receptors and endothelial products derived from cyclooxygenase, (2) the response to AI is, in part, produced by its conversion into AII.