Effect of converting enzyme inhibitors on prostaglandin synthesis by isolated glomeruli and aortic strips from rats

In addition to their effect on angiotensin and bradykinin metabolism, converting enzyme inhibitors (CEI) may also alter prostaglandin (PG) synthesis. We therefore examined two CEI, SQ 14,225 (captopril) and SQ 20,881, for their in vitro effect on PG synthesis by glomeruli and aortic strips from rats. Glomeruli incubated in test tubes produced predominantly PGE₂ and PGF(2α). Both CEI selectively stimulated PGE₂ synthesis with maximal effects at 25 μM. During superfusion of glomeruli with captopril (25 μM) synthesis of PGE₂ increased 5- to 10-fold and that of 6-keto-PGF(1α) doubled. No significant change in PGF(2α) or thromboxane B₂ occurred. This effect of CEI was independent of angiotensin or bradykinin. In contrast captopril had no effect on PG synthesis by aortic strips, which produced predominantly prostacyclin assayed as 6-keto-PGF(1α) and little PGE₂ and PGF(2α). These results demonstrate that CEI can directly stimulate PG synthesis in glomeruli. This additional mechanism of action of CEI may require reinterpretation of the role of angiotensin based on results obtained with CEI.