TRANSPORT OF L-CARNITINE INDUCED BY PREDNISOLONE IN AN ESTABLISHED CELL-LINE (CCL-27) - POSSIBLE EXPLANATION OF THE THERAPEUTIC EFFECT OF GLUCOCORTICOIDS IN MUSCULAR CARNITINE DEFICIENCY SYNDROME

Prednisolone (10-8-10-5 mol/l) in the growth medium for 24 h increased the rate of uptake of L-[3H]carnitine in an established cell line (CCL 27) to 164 ± 6% (mean ±S.E.) of the rate observed in untreated cells. At the same time the intracellular content of free L-carnitine increased about 20%. The simultaneous addition of prednisolone (10-6 mol.l for 24 h) and L-carnitine (10-4 mol/l for 96 h) to the growth medium increased the rate of uptake to 225 ± 8% (mean ±S.E.) of that in untreated cells. The increase seemed to be mediated through an increase in number of carriers, as judged by the increase in V of the transport process with unchanged Km. Phosphodiesterase I, an enzyme mainly localized in the plasma membrane, increased its activity about 3.5 times when cells were stimulated with prednisolone. Thus, it seems that the increase in the rate of uptake of L-carnitine mediated by glucocorticoids, is part of a more general effect on the plasma membrane. The observations offer an explanation to the observed clinical improvement in patients with muscular carnitine deficiency treated with glucocorticoids and/or L-carnitine. © 1979.