Regression of left ventricular hypertrophy and control of hypertension in the spontaneously hypertensive rat (SHR): Oxprenolol versus hydrochlorothiazide
The control of hypertension with antihypertensive agents, in the spontaneously hypertensive rats (SHR) can result in regression of established cardiac hypertrophy. This study compared the effects of therapy with oxprenolol (Ox) and with hydrochlorothiazide (Htz) for (1) regression of established left ventricular hypertrophy (LVH) and (2) blood pressure control. Three groups of SHR and 3 comparable groups of Wistar-Kyoto (WKY) rats, matched for age, sex and body wt, were treated with tap water (Gp I), 60-200 mg hydrochlorothiazide kg-1 day-1 (Gp II) and 15-500 mg oxprenolol kg-1 day-1 (Gp III) for 13 weeks. Systolic and diastolic blood pressures (SBP, DBP mmHg), left ventricular wt/body wt ratio (LVwt/Bwt mg g-1) and left ventricular wall thickness (LVWT mm) were recorded. Oxprenolol lowered both systolic (mean +/- S.E. mmHg, 130 +/- 7 vs 189 +/- 8; P less than 0.01) and diastolic blood pressures (mean +/- S.E. mmHg, 104 +/- 6 vs 159 +/- 6; P less than 0.001) and caused regression of left ventricular hypertrophy (mean +/- S.E. mg g-1, 2.91 +/- 0.06 vs 3.10 +/- 0.09; P less than 0.05). In contrast, hydrochlorothiazide did not control blood pressure (mean +/- S.E. mmHg, 183 +/- 5 vs 189 +/- 6 and 152 +/- 5 vs 156 +/- 6), but it did cause regression of left ventricular hypertrophy (mean +/- S.E. mg g-1, 2.67 +/- 0.03 vs 3.10 +/- 0.09; P less than 0.01). Left ventricular wall thickness, measured in the mid-ventricular region, was significantly reduced only by hydrochlorothiazide (mean +/- S.E. mm, 2.76 +/- 0.06 vs 3.21 +/- 0.01; P less than 0.05). These results suggest that regression of left ventricular hypertrophy can occur with or without control of hypertension in the SHR.