Left ventricular function and collagen content after regression of hypertensive hypertrophy

Abstract

To determine whether regression of hypertensive hypertrophy through blood pressure control also involves left ventricular collagen and consecutive alterations in left ventricular diastolic and systolic function, antihypertensive treatment with the calcium channel blocker nifedipine (30 mg/kg.day) was employed in 20-week-old spontaneously hypertensive rats (n = 15) for a period of 20 weeks. Age-matched (40 weeks old) untreated (n = 13) and 20-week-old spontaneously hypertensive rats representing the state before therapy (n = 14) were used for comparison. Myocardial stiffness was described by the tangent modulus Km of the elastic stiffness-stress relation. Left ventricular collagen was determined by means of hydroxyproline (OH-proline) concentration. Myocardial working capacity of the left ventricle was measured as the peak developed systolic pressure per weight unit muscle mass and systolic peak pump function as the maximum achievable cardiac output under volume loading. After the 20-week course of nifedipine treatment, systolic aortic pressure dropped from 187 +/- 11 to 144 +/- 6 mm Hg (p less than 0.001). Regression of hypertrophy was shown by a left ventricular muscle/body weight ratio of 2.13 +/- 0.18 mg/g (p less than 0.01) in the 40-week-old nifedipine-treated hypertensive rats, whereas the ratios of the 20-week-old and 40-week-old untreated spontaneously hypertensive rats were 2.3 +/- 0.30 and 2.34 +/- 0.18 mg/g, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)