CHANGES IN CREATINE-KINASE EXPRESSION INDUCED BY EXERCISE IN BORDERLINE HYPERTENSIVE RAT HEARTS

Hypertrophy in hypertensive hearts is associated with increased risk o f cardiac morbidity and mortality that is not characteristic of exerci sed hearts. This study was done to determine whether exercise training of normotensive and borderline hypertensive rats induces the increase d myocardial expression of BB and MB isoforms of creatine kinase (CK) that characterizes hypertensive hypertrophy. Spontaneously hypertensiv e (SHR), borderline hypertensive (BHR), and normotensive Wistar-Kyoto (WKY) rats were subjected to either an 8% sodium chloride diet or swim training to produce myocardial hypertrophy. Both exercise and a high salt diet induced an increase in the combined expression of CK-MB and CK-BB in SHR after 2 months. However, since swimming also exacerbated hypertension in SHR, exercise induced effects on CK were not distingui shable from those of hypertension. In WKY, neither exercise nor a high salt diet induced significant changes in CK isozyme expression. In BH R fed a high sodium chloride diet, significant increases in mean arter ial pressure and left ventricular weight to body weight were not assoc iated with changes in CK expression. In contrast, following 10 months of swim training BHR exhibited mild hypertrophy, decreased resting hea rt rates, and an increase in the combined expression of CK-MB and CK-B B. Therefore, exercise associated with a cardiac training effect in BH R induced changes in CK isozyme expression similar to those in hyperte nsive hearts.