Half-Life and Metabolism of ³H-Folic Acid in Oral Contraceptive Treated Rats

Summary

Half-life and tissue distribution of injected tritium labelled folate was examined in oral contraceptive (OCA) treated and control rats to elucidate the mechanism by which OCA treated rats show increased urinary excretion as well as tissue levels of folate. Urinary excretion of folate within the first 12 hours of injection was higher but subsequent excretion lower in OCA treated rats. Faecal excretion of folate was also lower in treated rats. Thus, the half-life of the rapid turnover labile pool of folate appears to be reduced, whereas that of the slow turnover stable pool is raised by OCA treatment. Concentration of labelled folate was higher in the liver and kidneys of treated rats but it was not affected in tissues such as intestine, bone and brain. The concentration of soluble folate binders in the kidney was raised by OCA treatment and the activity of dihydrofolate reductase in the liver (a folate binder) also tended to be higher though the difference was not significant. The observations suggest that OCA may alter folate turnover by changing the concentration of folate binders in the tissues.

Key-Words:

Oral Contraceptives - ( ³ H)-Folate Turnover - Folate Pools - Folate Half-Lives - Dihydrofolate Reductase - Folate Binders - Tissue Folate