Studies on the Interrelationship between Methionine and Vitamin B6

Abstract

Levels of methionine only slightly above those necessary for growth depressed the growth of rats fed limiting amounts of vitamin B₆. Vitamin B₆ counteracted the effects of moderate amounts of methionine. When the diet contained 2.5% of methionine, high levels of the vitamin failed to restore growth. D-, L- and DL-methionine and DL-homocystine were approximately equivalent in depressing growth; cystine did not depress growth. Acrodynia was aggravated by moderate amounts of methionine (D-, L- or DL-isomers), and by homocystine. Glycine, alanine, serine, cystine, threonine, and additional B vitamins did not affect growth when moderate levels of methionine were added to diets limiting or deficient in vitamin B₆. When the ration contained 1.0% of added methionine, the three forms of vitamin B₆ were approximately equal in promoting growth; in some experiments the most active form of the vitamin appeared to be pyridoxal. The consumption of pyridoxine decreased the excretion of free methionine in the urine of rats fed moderate amounts of the amino acid. Dietary methionine did not affect the concentration of vitamin B₆ in the blood or liver of rats.