EFFECTSTS OF CALCIUM ANTAGONISTS ON WITHDRAWAL OF β-RECEPTOR BLOCKERS IN RATS DURING LEFT VENTRICULAR HYPERTROPHY

The hemodynamic changes of metoprolol(Met,50mg·kg^-1·d^-1,po,3wk)withdrawal for 1 day the effects of nifedipine(Nif)and m-nifedipine(m-Nif)on these changes were observed in pressure overload hypertrophy in rats by abdominal aortic constriction for 4 wk.BothNif and m-Nif(10 mg·kg^-1·d^-1,respectively,po,3 wk)siginificantly attenuated the increase ofMAP(from 14.3±2.3 to 12.9±2.3 and 11.3±2.4kPa,respectively,n=6～7,P<0.05)anddecrease the abnormal development of systolic function of left ventricle after Met withdrawal.Radioreceptor assay indicates that Nif and m-Nif can prevent the up-regulation of myocardium β-receptors in left ventricular hypertrophy and large dose of Met exposure for a long time.These resultssuggest that calcium antagonists administratered with β-blockers can prevent β-receptor blockerwithdrawal syndrome.