In order to investigate the cardiac effects of antihypertensive therapies in one-clip two-kidney hypertension in rats, we compared the consequences on myosin isoenzyme profile and on left ventricular hypertrophy of two treatments: one was a new converting enzyme inhibitor (S9490), the second a more standard tripletherapy associating clonidine, dihydralazine and furosemide. The two treatments were initiated 4 weeks after clipping and administered during 5 weeks. During the treatment period average systolic blood pressure was 215 +/- 32 mmHg in the hypertensive untreated group (HC2, n = 12) and 144 +/- 13 mm Hg in the CEI group (HT1, n = 13), which is not significantly different from the value found in the sham-operated group (139 +/- 4 mm Hg, C2, n = 13). Blood pressure was lowered only to 173 +/- 18 mm Hg in the group treated with tripletherapy (HT2, n = 12). The left ventricular weight decreased significantly in the CEI-treated group toward values similar to those of the sham-operated animals (2.2 +/- 0.13 mg/g vs. 1.9 +/- 10 mg/g, respectively NS), whereas it did not change in the tripletherapy group when compared to the untreated hypertensive animals despite the fall in blood pressure. In the hypertensive untreated rats the percentage of V1 isoenzyme of cardiac myosin was lower than in the sham-operated group (42.8 +/- 9.0% vs. 57.5 +/- 7.6% P less than .001). In parallel the V3 form of cardiac myosin increased (24.1 +/- 7.4% vs. 15.7 +/- 4.3%, P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)