Effects of L-carnitine on tissue levels of acyl carnitine, acyl coenzyme A and high energy phosphate in ischemic dog hearts.

Abstract

To evaluate the protective effects of L-carnitine on ischemic myocardium, its effects on tissue levels of acyl carnitine, acyl CoA and high energy phosphate were studied in ischemic dog hearts. Myocardial ischemia was induced by the ligation of left anterior descending coronary artery for 15 min. L-carnitine (100 mg/kg) was administered i.v. prior to coronary ligation. In ischemic myocardium, tissue levels of free carnitine decreased from 1043 .+-. 358 to 623 .+-. 180 nmol/g (P < 0.001). Long chain acyl carnitine increased from 214 .+-. 54 to 498 .+-. 149 nmol/g (P < 0.001) and long chain acyl CoA increased from 15.7 .+-. 4.8 to 23.2 .+-. 5.4 nmol/g (P < 0.01). Pretreatment of L-carnitine increased tissue levels of free carnitine to 863 .+-. 318 nmol/g (P < 0.005) and decreased long chain acyl carnitine and long chain acyl CoA to 368 .+-. 128 nmol/g (P < 0.02) and 19.2 .+-. 6.5 nmol/g (P < 0.01), respectively. Tissue levels of ATP, that were reduced by myocardial ischemia from 5.43 .+-. 0.67 to 2.80 .+-. 0.58 .mu.mol/g (P < 0.001), was increased 3.28 .+-. 0.63 .mu.mol/g (P < 0.02) by L-carnitine. Positive correlation was observed between ATP and free carnitine (P < 0.01). Negative correlation was observed, not only between ATP and the ratio of long chain acyl CoA to free carnitine, but also between ATP and the ratio of long chain acyl carnitine to free carnitine (P < 0.01, respectively). The accumulation of long chain acyl carnitine may play an important role on cellular damage in ischemic myocardium; administration of exogenous L-carnitine is beneficial for the protection of ischemic myocardium, probably because it reduces the accumulation of long chain acyl carnitine and long chain acyl CoA.