Investigation of the influence of theophylline feeding on total, free, short-chain acyl and long-chain acyl carnitine levels in skeletal muscle and liver of rats.

L-carnitine, the obligate fatty acyl carrier across the inner mitochondrial membrane, is sensitive to biochemical changes that alter lipid metabolism. The present study describes the effects of oral theophylline on L-carnitine concentrations in the skeletal muscle and the liver of rats. A significant rise in total, free and long-chain acyl carnitine concentrations was observed in the skeletal muscle but not in the liver. The increases observed after the first week of theophylline feeding returned to the control concentrations after fifth week despite the continuation of treatment. The observed changes in the skeletal muscle may be due to a) increased acyl carnitines that are formed as a consequence of enhanced fatty acid mobilization and b) increased L-carnitine uptake by the tissue.