Effect of L-carnitine supplementation on xenobiotic-metabolizing hepatic enzymes exposed to methanol.

The study aimed to evaluate the effect of L-carnitine on hepatic cytochrome P450-dependent monooxygenases exposed to methanol. Male Spraque-Dawley rats were given methanol (1/4 LD50 and 1/2 LD50) together with L-carnitine (1g/kg body weight). The parameters of microsome electron transport chains I and II and the levels of CYP2E1, CYP2B1/2 and CYP1A2 were measured 8, 12, 24, 48, 72 and 96 h after exposure. L-carnitine did not affect cytochrome P450 but it significantly increased at 72 and 96 h NADPH-cytochrome P450 reductase. It stimulated cytochrome b5 at 48 and 96 h and NADH-cytochrome b5 reductase activity at 12, 72 and 96 h. Methanol, especially the lower dose, inhibited cytochrome P450 after 48 h, but the higher methanol dose inhibited NADH-cytochrome b5 reductase activity in this time. L-carnitine, combined with the lower dose of methanol, stimulated NADPH-cytochrome P450 reductase after 48 h and cytochrome b5 and NADH-cytochrome b5 reductase over the whole period of observation. L-carnitine stimulated CYP2B1/2 but not CYP2E1 and CYP1A2. Methanol stimulated CYP2E1 at 24 h, but CYP1A2 at 96 h in the studied doses. CYP2B1/2 was induced by the lower dose of methanol at 24 h but by the higher one at 96 h. When given together, L-carnitine and methanol (1/2 LD50) significantly stimulated CYP2E1 up to 170% at 24 h and 145% at 96 h.

Effect of methanol on endogenous and exogenous carnitine levels in rat plasma.

The effect of methanol on the levels of endogenous carnitine and its derivatives was studied in male Sprague-Dawley rats aged three months. In addition, the effect of L-carnitine supplementation on metabolic disturbances caused by methanol intoxication was studied. The rats were randomized into six groups, including two control groups. Methanol was given at 1/4 LD(50) and 1/2 LD(50)/kg b.w. (or water in control) through an intragastric tube, and L-carnitine (or 0.9% NaCl in the control) was injected intraperitoneally. The levels of plasma L-carnitine and its derivatives were measured at selected time points for four days. Following methanol administration, the rats exhibited dose-dependent increases in L-carnitine levels and altered ratios of L-carnitine and its derivatives. L-carnitine supplementation accelerated the normalization of metabolic disturbances, as indicated by the acylcarnitine to free carnitine ratio (AC/FC). The protective effect of L-carnitine is supported by the fact that 100% of the methanol-treated rats supplemented with carnitine survived, while 8/60 rats and 27/101 rats died at methanol doses of 1/4 LD(50) and 1/2 LD(50), respectively, in groups without L-carnitine supplementation.