Vitamin B-6 metabolism and turnover in the ethanol-fed rat

The effect of long-term ethanol supplementation on vitamin B-6 metabolism and storage was studied in McCollum rats receiving approximately 30% of their caloric intake as ethanol. Hepatic pyridoxal 5'-phosphate levels were significantly depressed in the ethanol-fed animals. However, total hepatic vitamin B-6 levels were slightly higher than in control animals because of a marked increase in pyridoxamine 5'-phosphate levels. The metabolism of a labeled pyridoxine dose appeared unaffected by ethanol administration, with the final distribution of labeled metabolites, almost entirely pyridoxal 5'-phosphate and pyridoxamine 5'-phosphate, mirroring that observed with unlabeled endogenous vitamin B-6. The daily turnover of total-body vitamin B-6 stores in ethanol-fed animals (2.7%) was lower than in control animals (3.8%). Whether this resulted from ethanol administration or a reduced vitamin B-6 intake was not ascertained. However, it was apparent that ethanol did not increase the turnover of total-body vitamin B-6 or decrease total-body stores of the vitamin, which were similar in both groups of animals on a body store per kilogram weight basis. Pyridoxic acid excretion reflected vitamin B-6 intake in both groups of animals and accounted for approximately 30% of the total excreted vitamin.