Folate Activity in Tissues of Rats on Folate-Free Diets. ∗

Abstract

Summary

Rats kept on a folate-free diet were found to have decreased folate activity in kidneys, livers and blood in comparison with control animals kept on a mixed standard diet. In the kidneys the drop in folate activity amounted to 70% after 10 days, and to about 85% after 20 days. No appreciable differences were encountered, regardless of whether or not the kidneys were autolyzed prior to the bioassay, or whether the bio-assay was performed with L. casei or P. cerevisiae. A 40% drop in folate activity was found in livers of animals kept on a folate-free diet for 10 days; the drop amounted to 80% after 20 days. These results were obtained when autolyzed tissues were employed in the bioassay. Livers assayed without prior autolysis showed very low activity with P. cerevisiae because of the high contents of methyl-tetrahydrofolate of the liver. After autolysis similar activities were obtained with both assays. Decreased blood folate activity was found in rats only after they had been kept for 20 days on the deficient diet. Thus, decreased folate activity in the blood indicates a severe depletion of the tissue stores. Rats kept on a synthetic diet supplemented with PGA (20 or 4 mg/kg diet) showed a higher liver and blood folate activity than control rats fed on mixed standard diet. The livers of both groups showed almost double folate activity when assayed on autolyzed samples than when done without such treatment. Autolysis presumably made available to L. casei forms of folates (e.g., polyglutamates) to which it could not respond prior to the treatment.

The valuable technical assistance of Mrs. M. Jab-lonska is gratefully acknowledged.