Carnitine transport and tissue carnitine accretion in rats

In rats, circulating carnitine levels were highly correlated with skeletal muscle and heart carnitine concentrations over the range of 26-69 microM serum carnitine, but not at higher extracellular carnitine concentrations (70-188 microM). By contrast, circulating carnitine levels over the entire range studied (26-188 microM) correlated with liver and kidney carnitine concentrations. For each tissue the range of extracellular carnitine concentrations which correlated with the tissue carnitine concentration corresponded with the linear or nearly linear portion of the Michaelis-Menten curve for transport of carnitine in vitro.