EFFECT OF PYRIDOXINE DEFICIENCY ON NUCLEIC ACID METABOLISM IN THE RAT.

1. The nucleic acid metabolism in the pyridoxine-deficient rat has been investigated through studies on the incorporation of radioactivity from various isotopically labelled compounds into liver and spleen DNA and RNA. 2. In pyridoxine deficiency, the incorporation of radioactivity from sodium [(14)C]formate was apparently increased. The magnitude of this effect on incorporation into liver RNA and DNA and spleen RNA was approximately the same. The incorporation into spleen DNA was enhanced to a much greater degree. Administration of pyridoxine 24hr. before the rats were killed reversed the changes in incorporation of radioactivity from [(14)C]formate. 3. In pyridoxine deficiency, the incorporation of radioactivity from dl-[3-(14)C]serine, [8-(14)C]adenine, [Me-(3)H]thymidine and [2-(14)C]deoxyuridine was decreased. The incorporation of radioactivity from l-[Me-(14)C]methionine was not affected. No noteworthy differences in the effect of pyridoxine deficiency on the incorporation of radioactivity from dl-[3-(14)C]serine into DNA and RNA were observed, whereas the effect of the deficiency on the incorporation of radioactivity from [8-(14)C]adenine into spleen DNA was somewhat greater than that into spleen RNA. Administration of pyridoxine 24hr. before the rats were killed reversed the changes in incorporation of radioactivity from [3-(14)C]serine and [8-(14)C]adenine. 4. The adverse effects of pyridoxine deficiency on the biosynthesis of nucleic acids and cell multiplication are discussed in relation to the role of pyridoxal phosphate in the production of C(1) units via the serine-hydroxymethylase reaction.