Comparative acute effects of l-carnitine and dl-carnitine on hepatic catabolism of l-alanine and l-glutamine in rats

AIM: To compare the acute effects of l-carnitine (LCT) and dl-carnitine (DLC) on hepatic catabolism of l-alanine and l-glutamine in rats. METHODS: Livers from 24 h fasted and fed rats were perfused in situ. The substrates l-alanine (5 mmol/L) and l-glutamine (5 mmol/L) were employed. The gluconeogenic and ureogenic activity was measured as the difference between the rates of glucose and urea released during and before the infusion of l-glutamine or l-alanine. RESULTS: LCT (60 micromol/L) but not DLC (60 micromol/L and 120 micromol/L) increased the production of glucose and urea from l-glutamine. However, neither LCT (60 micromol/L and 120 micromol/L) nor DLC (60 micromol/L and 240 micromol/L) showed any significant effect on hepatic glucose and urea production from l-alanine. CONCLUSION: The results showed a different acute effect of LCT and DLC on the activation of hepatic gluconeogenesis and ureagenesis promoted by l-glutamine, reinforcing the idea that DLC could not replace LCT.