PROPIONYL-L-CARNITINE PREVENTS MYOCARDIAL MECHANICAL ALTERATIONS DUE TO PRESSURE-OVERLOAD IN RATS

This study investigated if propionyl-L-carnitine (PLC) treatment can d irectly affect cardiac mechanics, secondary to increase in myocardial carnitine content, in rats with aortic constriction and sham-operated controls. After weaning, rats were fed one of the following diets for 8 wk: 1) a low-carnitine diet (containing 2 nmol/g carnitine); 2) the same diet supplemented with PLC (710 mu mol/kg body wt); 3) L-carnitin e (LC; 118 mu mol/kg body wt, given in tap water; or 4) a standard die t (containing 56 nmol/g carnitine). A 4-wk. constriction of the abdomi nal aorta caused left ventricular hypertrophy associated with signific antly prolonged timing parameters and reduced rate of tension decay in papillary muscles. In group 2, however, PLC treatment prevented hyper trophy-induced changes in these parameters and the reduction in unload ed shortening velocity in skinned trabeculae. Finally, PLC treatment m aintained the relative proportion of myosin heavy chain isoforms in le ft ventricular wall of animals subjected to aortic constriction. Both PLC and LC completely prevented carnitine depletion due to hypertrophy and to dietary restriction. Because LC did not modify papillary muscl e contractile function, these results demonstrate that PLC affects hyp ertrophy-induced changes in muscle mechanics and ventricular wall comp osition independently of tissue carnitine levels.