NIFEDIPINE IN DIVIDED DOSES DOES NOT REVERSE LEFT-VENTRICULAR HYPERTROPHY IN SPONTANEOUSLY HYPERTENSIVE RATS

This study investigated whether nifedipine administered in divided daily doses would diminish left ventricular hypertrophy (LVH) in spontaneously hypertensive rats (SHR). We administered nifedipine (12 mg/kg/day) in 3 divided doses by gastric gavage to 15-week-old male SHR (n = 10) for 4 weeks. Age- and sex-matched SHR served as controls (n = 10), Left ventricular (LV) function was evaluated by LV catheterization and cardiac output was determined by the thermodilution method. Plasma renin activity (PRA) and plasma norepinephrine levels were measured. Nifedipine significantly decreased blood pressure (p < 0.01), shortened time constant T (p < 0.05), and increased cardiac output (p < 0.05). Nifedipine did not impair the LV systolic and diastolic indices during acute afterload elevation with angiotensin II. LV weight was similar in the 2 groups of rats. While PRA was unaltered, plasma norepinephrine levels were higher in the nifedipine-treated rats (p < 0.05). These data indicate that nifedipine in 3 divided doses reduced blood pressure in SHR without compromising cardiac function bud did not reverse LVH. The short hypotensive duration of nifedipine and its enhancement of sympathetic nervous activity may be responsible for the failure to reverse LVH, despite adequate blood pressure control.