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Mitochondrial respiration was studied in the presence of carnitine or acetyl-carnitine isomers. The results demonstrate that 15 mM L-acetylcarnitine stimulates oxygen consumption by approximately 25%. D-acetylcarnitine (15 mM) had a slight inhibitory effect whereas racemic DL-acetylcarnitine (15 mM) markedly inhibited mitochondrial respiration. Similarly racemic DL-carnitine showed approximately 60% inhibition of mitochondrial respiration. L-carnitine or D-carnitine showed no significant effect on oxygen consumption. Further studies will be required to establish whether the carnitine or acetylcarnitine isomers competitively inhibit the acylcarnitine translocase systems of the mitochondrial membrane.

L-acetylcarnitine is a compound with cholinergic properties and putative action on the visual system and the glucose metabolism. Ten healthy, emmertropic volunteers (age range: 21 to 28 years) were studied. Each subject was administered 5, 10, and 30 mg/kg acute intravenous doses of L-acetylcarnitine and matching placebo. Retinal oscillatory potentials to full-field flash stimulation were recorded before and 30, 60, and 120 min after administration. A systematic reduction of the implicit time of the P2 and N2 oscillatory potential components was observed after administration of the 10 and 30 mg/kg doses: significant changes were not evident at the 5 mg dose or after placebo. The latency reduction was significantly correlated with the postdrug increment of the L-acetylcarnitine plasma concentration. No other systematic modification in latency of amplitude was observed.

The enzyme carnitine acetyltransferase (acetyl-CoA:carnitine O-acetyltransferase, EC 2.3.1.7) has been purified to homogeneity from hepatic mitochondria of clofibrate-fed rats. It is a protein of molecular weight 56 000 composed of two non-identical subunits of molecular weight 34 000 and 25 000. The enzyme is inhibited by palmityl-CoA as well as acetyl carnitine. The inhibition by fatty acyl-CoA is competitive with respect to both the substrates, carnitine and acetyl-CoA. The inhibition by acetylcarnitine is reversed by carnitine but not by acetyl-CoA.

One of the causative agents of the African Trypanosamiases, Trypanosoma brucei brucei is able to use high intracellular carnitine concentrations and a high carnitine acetyl transferase (CAT) activity to stimulate ATP production. This paper reports that a carnitine analogue, bromoacetyl-L-carnitine, is an irreversible inhibitor of CAT from T.brucei, non-competitively inhibits carnitine uptake by T.brucei and has a potent in vitro effect against T.brucei motility and infectivity. An in vivo action in T.brucei infected mice is also reported. These results represent a new area of investigation in the important search for new antitrypanosomal agents.

The effects of methylazoxymethanol acetate (MAM) administered on the 15th gestational day, and of acetyl-L-carnitine treatment, on rat brain total and ribosomal RNA levels, were studied. In the brain of MAM-treated rats both total and ribosomal RNA concentrations were significantly reduced. Acetyl-L-carnitine treatment restored total and ribosomal RNA levels. The frontal cortex and the hippocampus were the brain areas most sensitive to acetyl-L-carnitine administration. Histochemical demonstration of tissue stores of nucleic acids showed that the loss of RNA induced by MAM occurs primarily within the cytoplasm of nerve cells in various telencephalic areas. Neuronal cytoplasmatic RNA is also sensitive to acetyl-L-carnitine treatment.