Fig. 2.

Determination of deuterated acylcarnitine production rates in whole blood samples (a) The profiles of the rates at which individual deuterated acylcarnitines were formed from deuterated palmitate were determined simultaneously in whole blood samples from the patient and a healthy control. Weighted reference range values (5th to 95th percentile interval, n = 52) are given in the pink colored backgrounds. These profiles are usually determined to identify an impediment of mitochondrial fatty acid oxidation and to locate the site of the underlying enzyme failure. The blockade is here upstream to mitochondrial long-chain acylcarnitine formation, explaining why formation of all the individual acylcarnitines is strongly reduced and is thus consistent with a defect in the type 1 carnitine palmitoyltransferase, which physiologically produces long-chain acylcarnitines. (b) CPT1 is assayed by the ability of whole blood to generate deuterated palmitoylcarnitine from deuterated palmitate over short incubation time periods. Results are given as mean values of three separate determinations. It is assumed that the acyl-CoA synthetase, which precedes action of CPT1 is not rate limiting, a view corroborated by similar extents to which patient CPT1 is deficient in the present measurements and those performed on skin fibroblasts (see Table 1)