ANGIOTENSIN-CONVERTING ENZYME-INHIBITOR, CAPTOPRIL, INHIBITS CARDIAC-HYPERTROPHY WITHOUT CHANGING COLLAGEN TYPES AND CONCENTRATION IN SPONTANEOUSLY HYPERTENSIVE RATS

1. The effects of the ACE inhibitor, captopril, on collagen metabolism in spontaneously hypertensive rats (SHR) with cardiac hypertrophy was examined. Captopril (100 mg/kg per day) was administered in drinking water to 20 week old male SHR for 12 weeks. Collagen concentration was calculated from hydroxyproline content, and relative proportions of t ypes I, III and V collagen were determined by non-interrupted SDS-poly acrylamide gel electrophoresis (SDS-PAGE). These parameters were exami ned in age and sex matched Wistar-Kyoto (WKY) rats, as well as in non- treated SHR, and compared with those of captopril-treated SHR. 2. Capt opril significantly reduced both blood pressure (191 +/- 12.1 vs 146 /- 11.2 mmHg, P<0.01), and the ratio of left ventricular (LV) weight t o bodyweight (BW; 2.38 +/- 0.17 vs 2.05 +/- 0.12 mg/g, P<0.01). There were no significant differences in collagen concentration among WKY ra ts, captopril-treated SHR and non-treated 32 week old SHR. However, to tal collagen content in captopril-treated SHR reduced significantly co mpared with non-treated 32 week old SHR (16.8 +/- 2.0 vs 21.3 +/- 0.8 mg, P<0.01). The relative proportion of type V collagen was significan tly higher in both captopril-treated (58.6 +/- 3.4 vs 46.8 +/- 1.3%, P <0.01) and non-treated 32 week old SHR (59.9 +/- 3.1 vs 46.8 +/- 1.3%, P<0.01) compared with WKY rats. However, there were no significant di fferences between captopril-treated SHR and non-treated 32 week old SH R. 3. The data from this study showed that captopril reduced cardiac h ypertrophy, as reported previously, but did not change collagen types and concentration of the hypertrophied myocardium in SHR.