Interorgan cooperativity in carnitine metabolism in the trained state

This study was designed to evaluate the effects of chronic exercise training on carnitine acetyl- and palmitoyltransferase activity and the distribution of carnitine forms and concentrations in various organs and tissues of female rats. Sprague-Dawley rats were swim trained 6 days/wk and progressed to 75-min swims twice daily (with 3% of their total body weight attached to the medial portion of the tail) at the end of 5 wk of training. Sedentary (S, n = 12) and trained (T, n = 13) animals were killed by decapitation, and the livers, kidneys, hearts, and several skeletal muscle types were removed and immediately frozen in liquid N2 and/or extracted for enzyme activity assays. Blood was collected and plasma was stored frozen. Samples were assayed for free, acid-soluble, and acid-insoluble carnitine. Free carnitine increased significantly (P less than 0.03) in T hearts. Free carnitine remained unchanged in liver, but short-chain acylcarnitines increased significantly (P less than 0.001). There was a significant (P less than 0.001) reduction in long-chain acylcarnitines in kidney in the trained rats, and plasma short-chain acylcarnitine levels also decreased (P less than 0.001). Several significant changes in carnitine distribution also occurred in the superficial and deep portions of the vastus lateralis and in the mixed gastrocnemius muscles. There was a significant reduction in carnitine acetyltransferase activity with training in both the soleus (P less than 0.02) and superficial gastrocnemius (P less than 0.002) muscles. The deep portion of the gastrocnemius muscle contained significantly higher activity than either the superficial portion or the soleus.(ABSTRACT TRUNCATED AT 250 WORDS)