Enzymological determination of free carnitine concentrations in rat tissues

Purified carnitine acetyltransferase was employed to catalyze the reaction:Carnitine+acetylCoA⇌acetylcarnitine+CoA. In the presence of a known excess of acetyl CoA, free CoA released was determined simultaneously in a coupled spectrophotometric assay. CoA formed was shown to be directly related to carnitine initially present. Rat tissue extracts were analyzed using this method, and μmoles of (–)-carnitine per gram dry weight were found to be 4.87 for heart; 3.14 for brown adipose tissue; 2.68 for skeletal muscle; 1.74 for testes; 1.26 for kidney; 0.55 for brain; and 0.051 for serum. The specificity and accuracy of the determinations are described.