Dose-dependent effects of angiotensin converting enzyme (ACE) inhibitors on glomerular prostanoid production by normotensive rats.

1. This study was designed to investigate whether the angiotensin converting enzyme (ACE) inhibitors, captopril, enalapril and fosinopril have a dose-dependent effect on the production of prostaglandin E2 (PGE2), prostaglandin I2 (prostacyclin, PGI2) and thromboxane A2 (TxA2) by glomeruli isolated from normotensive Wistar-Kyoto rats. 2. Measurements of glomerular prostanoid production were made under basal conditions and in the presence of excess exogenous arachidonic acid. 3. All three ACE inhibitors demonstrated dose-dependent effects upon glomerular prostanoid production which varied with the individual ACE inhibitor. 4. Enalapril induced a dose-dependent increase in the ratio of (PGE2 + PGI2)/TxA2, from 2.17 +/- 0.20 to 5.35 +/- 0.84 and to 10.0 +/- 1.16 with the low and high doses of enalapril respectively. In contrast, the high dose of captopril tended to reduce the ratio when compared to the low dose. 5. The results obtained in this study suggest that although all three ACE inhibitors appear to induce prostacyclin synthetase and/or modulate phospholipase A2 (PLA2) activity, these effects differ with the ACE inhibitor studied and the dose employed. 6. This study has demonstrated dose-dependent effects of three ACE inhibitors on glomerular prostanoid production which may be significant in modulating glomerular haemodynamics and growth characteristics of glomerular cells.