J Neurochem. 1981 Feb.
The uptake of carnitine by slices of rat cerebral cortex.
Huth PJ, Schmidt MJ, Hall PV, Fariello RG, Shug AL.

The properties of carnitine transport were studied in rat brain slices. A rapid uptake system for carnitine was observed, with tissue-medium gradients of 38 +/- 3 for L-[14CH3]carnitine and 27 +/- 3 for D-[14CH3]carnitine after 180 min incubation at 37 degrees C in 0.64 mM substrate. Uptake of L- and D-carnitine showed saturability. The estimated values of Km for L- and D-carnitine were 2.85 mM and 10.0 mM, respectively; but values of Vmax (1 mumol/min/ml intracellular fluid) were the same for the two isomers. The transport system showed stereospecificity for L-carnitine. Carnitine uptake was inhibited by structurally related compounds with a four-carbon backbone containing a terminal carboxyl group. L-Carnitine uptake was competitively inhibited by gamma-butyrobetaine (Ki = 3.22 mM), acetylcarnitine (Ki = 6.36 mM), and gamma-aminobutyric acid (Ki = 0.63 mM). The data suggest that carnitine and gamma-aminobutyric acid interact at a common carrier site. Transport was not significantly reduced by choline or lysine. Carnitine uptake was inhibited by an N2 atmosphere, 2,4-dinitrophenol, carbonylcyanide-N-chlorophenylhydrazone, potassium cyanide, n-ethylmaleimide, and ouabain. Transport was abolished by low temperature (4 degrees C) and absence of glucose from the medium. Carnitine uptake was Na+-dependent, but did not require K4+ or Ca2+.

Categories: Year-1981, Carnitine, GABA