ACETYLCARNITINE INHIBITS ALCOHOL-DEHYDROGENASE

Carnitine and acetylcarnitine are used as dietary supplements and as t herapeutic agents. Carnitine attenuates ethanol metabolism in intact a nimals but the in vitro activities of alcohol dehydrogenase (ADH), mic rosomal ethanol oxidizing system (MEOS) or catalase are not significan tly altered by carnitine. Since acetylcarnitine was a far more potent inhibitor of ethanol oxidation than carnitine in hepatocytes, the acti vities of rat liver ADH and MEOS were determined with or without acety lcarnitine. The activity of ADH, not MEOS, was significantly inhibited by acetylcarnitine at NAD : acetylcarnitine less than or equal to 1. The inhibition is of a competitive nature where acetylcarnitine compet es with NAD(+) (Ki = 135 mu mol.L(-1)). This finding is unique in that this is the first report of this function of acetylcarnitine and it i s a novel interaction between two important nutrients, niacin and carn itine. (C) 1994 Academic Press, Inc.