Reversal by acetylsalicylic acid of the captopril-induced inhibition of angiotensin converting enzyme in the hindquarters of guinea-pig.

The conversion of angiotensin I to angiotensin II was studied in the isolated perfused hindquarters of guinea-pig. The relative enzyme activity was determined by vasoconstrictor response to the peptides and by the contraction of rat ascending colon superfused with the venous effluent. 45% of conversion of angiotensin I to angiotensin II was determined in this preparation as measured by vasoconstrictor responses. However, only 22% of conversion was detected in the venous return as measured in the rat colon. Captopril significantly inhibited angiotensin converting enzyme activity in this preparation. Acetylsalicylic acid, however, partially prevented the inhibitory effect of Captopril on converting enzyme activity in this vascular bed. The possible interactions of angiotensin converting enzyme activity and endogenous prostaglandins are discussed.