CHRONIC EXERCISE AFFECTS VITAMIN-B-6 METABOLISM BUT NOT REQUIREMENT OF GROWING RATS

The effect of chronic exercise (forced swimming) on vitamin B-6 status and metabolism was studied in growing male rats fed deficient (0 mg p yridoxine-HCl/kg), suboptimal (2 mg pyridoxine-HCl/kg) or control (7 m g pyridoxine-HCl/kg) diets for 9 wk, Sedentary rats were fed the same diets, Body weight gain was lower in deficient rats than in both other dietary groups. Sedentary rats were heavier than trained rats of all diet groups. Erythrocyte aspartate aminotransferase, urinary 4-pyridox ic acid excretion, blood (plasma and erythrocytes) and tissue B-6 vita mers were measured. Urinary 4-pyridoxic acid, plasma pyridoxal 5'-phos phate and erythrocyte aspartate aminotransferase values of exercised a nd sedentary rats responded to changes in dietary pyridoxine but were not different from one another. After 9 wk of vitamin B-6 depletion, t issue concentrations of pyridoxal 5'-phosphate and pyridoxamine 5;5'-p hosphate were 41-66% and 26-49% lower, respectively, in the deficient groups than in the control groups, Larger percentage differences occur red in plasma than in tissues (95 vs. 22-66%), In liver, pyridoxal 5'- phosphate concentrations were lower, whereas pyridoxal concentrations were higher in trained than in sedentary rats. In gastrocnemius muscle , pyridoxal 5'-phosphate, pyridoxamine 5'-phosphate and total vitamin B-6 concentrations were higher in trained than in sedentary rats, Conc entrations of vitamin B-6 compounds in heart, kidneys, brain and adren als were not affected by training. On the basis of the vitamin B-6-dep endent variables measured in this study, we conclude that prolonged ex ercise affects the metabolism of vitamin B-6, but does not increase th e vitamin B-6 requirement in growing rats.