EFFECTS OF CARNITINE AND ITS DERIVATIVES ON GASTRIC-ACID SECRETION INRATS

Carnitine is a natural substance that acts as a carrier of fatty-acids across the inner mitochondrial membrane for subsequent P-oxidation. A cetyl-L-carnitine is the acetyl derivative of L-carnitine that has bee n shown to possess a slight cholinomimetic activity. Its success in sp orts medicine is dependent on the fact that it is able to stimulate th e central nervous system functions. This study aims to investigate the effects of L-carnitine (LC) and its derivatives-acetyl-L-carnitine (A LC) and propionyl-L-carnitine (PLC)-on gastric acid secretion in rats. A concentration-dependent relationship with both ALC or PLC was obser ved in experiments in vitro using a rat isolated stomach. The addition of atropine to the perfusion bath only partially antagonized the effe cts of the two compounds. Stimulation of gastric acid secretion in a d ose-dependent manner was also found when the tested compounds were adm inistered i.v. to anaesthetized rats. To elucidate the mechanism of th e gastric secretory response, assay for acetylcholine esterase activit y using acetylthiocholine as substrate, was performed. It was found th at ALC and PLC inhibited acetylcholine esterase, however, the ICS, for both compounds was about four times of magnitude greater than that of eserine. As the increase of the gastric acid secretion promoted by ca rnitines was blocked only partially by atropine both in vitro and in v ivo, whilst it was completely abolished by experimental degeneration o f the sympathetic neurons or by blockade of the postsynaptic sympathet ic receptors, it is suggested that the effect of carnitines is determi ned by cholinergic and partly by adrenergic mechanisms. (C) 1996 The I talian Pharmacological Society.