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The Uptake of Carnitine by Slices of Rat Cerebral Cortex
Author(s) -
Huth P. J.,
Schmidt M. J.,
Hall P. V.,
Fariello R. G.,
Shug A. L.
Publication year - 1981
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1981.tb01647.x
Subject(s) - carnitine , chemistry , incubation , acetylcarnitine , ouabain , choline , biochemistry , dinitrophenol , sodium , organic chemistry
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‐[ 14 CH 3 ]carnitine and 27 ± 3 for D‐[ 14 CH 3 ]carnitine after 180 min incubation at 37°C in 0.64 mM substrate. Uptake of L‐ and D‐carnitine showed saturability. The estimated values of K m for L‐ and D‐carnitine were 2.85 mM and 10.0 mM, respectively; but values of V max (1 μmol/min/ml in‐tracellular 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 γ‐butyrobetaine ( K i = 3.22 mM), acetylcarnitine ( K i = 6.36 mM), and γ‐aminobutyric acid ( K i = 0.63 mM). The data suggest that carnitine and γ‐aminobutyric acid interact at a common carrier site. Transport was not significantly reduced by choline or lysine. Carnitine uptake was inhibited by an N 2 atmosphere, 2,4‐dinitrophenol, carbonylcyanide‐ N ‐chlorophenylhydrazone, potassium cyanide, n‐ethylmaleimide, and ouabain. Transport was abolished by low temperature (4°C) and absence of glucose from the medium. Carnitine uptake was Na + ‐dependent, but did not require K + or Ca 2+ .