Evaluation of the impact of theophylline treatment on carnitine acetyltransferase activity in rat kidney.

We have previously reported that theophylline administration (100 mg/kg bw/day) changes the levels of carnitine in the plasma and tissues of rats. The objective of this study was to investigate the effect of theophylline treatment on the activity of carnitine acetyltransferase (CAT) in rat kidney. CAT catalyzes the reversible transfer of short-chain acyl groups across the inner mitochodrial membrane. Results showed that a significant increase in the activity of CAT was observed in kidney theophylline-treated groups as compared to either control or placebo groups (P < 0.01). The ratio of total carnitine (TC) levels to CAT activity was significantly increased in theophylline-treated rats as compared to either control or placebo groups (P < 0.01). Moreover, the results showed a positive correlation between the kidney TC and CAT activity (P < 0.01), whereas they showed a positive correlation between plasma levels of TC and kidney levels of TC (P < 0.01). These changes in activity CAT as well as TC levels might be due to the result from theophylline-enhanced mobilization of lipid from adipose tissues which consequently stimulated an increased carnitine transport into the kidney tissues to form fatty acyl-carnitine groups for subsequent beta-oxidation inside the mitochondria.