Carnitine in human polymorphonuclear leukocytes, mononuclear cells, and platelets.

We tried to study the distribution of carnitine in human blood. Total carnitine (free plus acylcarnitine) was determined in red blood cells, polymorphonuclear leukocytes, mononuclear cells, platelets, and plasma from 15 apparently healthy adults. We did not find carnitine in red blood cells but found it in significant amounts in polymorphonuclear leukocytes and mononuclear cells, 52.2 +/- 16.9 and 41.9 +/- 9.3 mumol/10(9) cells (mean +/- 1 SD), respectively. We also found that platelets contain carnitine in small amounts, 49.0 +/- 8.4 nmol/10(9) cells. In plasma the carnitine concentration was 51.5 +/- 3.3 mumol/L. We conclude that blood carnitine is localized mainly in polymorphonuclear leukocytes and mononuclear cells (83% of whole-blood carnitine).