Aim: Myocardial nuclear caIcium transport was investigated on the model of isoproterenol (ISO) induced cardiac hypertrophy.Methods: Rats were given injections of ISO subcutaneously (20, 10 and 5 mg/kg/day for 3 days, subsequently 3 mg/kg/day for 7 days). Myocardial nuclei were purified with sucrose density centrifugation and identified zymologically, the activity of Ca2+-ATPase was measured zymololgically and calciurn uptake was assayed with 45 Ca2+ isotope.Results: The ratio of heart weight to body weight in ISO group increased by 40% (P<0.01), and ISO-injured heart presented typical cardiac hypertrophy and interstitial fibrosis. Collagen and calcium content in myocardial tissue increased by 81 % and 41 % respectively (P<0.05). Vmax and Km of ATPase activity decreased by about 24% and 46. 1 % respectively (P<0. 05 ). Significant decrease of nuclear Ca2+ uptake was observed and Vmax value was lowered by 62 % compared with that of control(P<0. 01 ), but Km value remained unchanged.Conclusion: The above results indicated a dysfunction of nuclear calcium transport in hypertrophic myocardium.