An improved and simplified radioisotopic assay for the determination of free and esterified carnitine.

The radioisotopic assay for carnitine first described by Cederblad and Lindstedt (Clin. Chim. Acta. 37:235-543, 1972) and modified by Bohmer et al (Clin. Chim. Acta. 57:55-61, 1974) has been improved and simplified. As a result, the assay yields a linear response over a wide range of carnitine concentrations without the need for excessive amounts of labeled acetyl-CoA. In addition, it will measure very small quantities of carnitine even in the presence of excess acylcarnitine. The method allows rapid determination of free and esterified carnitine in small volumes of plasma (50 mul is sufficient) without the need for prior deproteinization of the samples.