RENAL ADAPTATION TO DIETARY CARNITINE IN HUMANS

Carnitine homeostasis in humans is maintained by dietary carnitine int ake, a modest rate of endogenous carnitine synthesis, and efficient co nservation of carnitine by the kidney. To assess the effect of dietary carnitine on the efficiency of carnitine reabsorption in humans, rate s of carnitine excretion and reabsorption, indexed to the glomerular f iltration tate, were determined over a range of plasma free and total carnitine concentrations in 12 strict vegetarians before and after die tary carnitine supplementation (0.248 mmol/d). This amount of dietary carnitine supplementation did not significantly increase plasma carnit ine concentration and did not alter the glomerular filtration rate. At normal physiological plasma carnitine concentrations, the rate of car nitine excretion was increased and the rate of carnitine reabsorption was decreased by carnitine supplementation. We conclude that the kidne y adapts to carnitine intake by reducing the efficiency of carnitine r eabsorption.