The Role of Folic Acid Binding Proteins (FABP) in the Cellular Uptake of Folates

Samuel Waxman, Carol Schreiber

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

HeLa cells and human lymphocytes were grown in complete media or conditioned in folate deficient media and were used to study the physiology of folic acid binding proteins (FABP). The uptake of tritiated folic acid (3HPGA) and N-5-methyl tetrahydrofolic acid (3H methyl-THFA) by folate replete HeLa cells increased for 3 hr, was temperature dependent, was greater for 3H methyl-THFA than 3HPGA and was not influenced by preincubation with Dilantin or ethanol. HeLa cells conditioned in folate deficient media after 1 week exhibited deranged DNA synthesis (abnormal deoxyuridine suppression of 3H thymidine into DNA and a decreased growth curve) which was progressive with degree of folate deficiency. The uptake of 3HPGA and 3H methyl-THFA was greater (five and three times, respectively) in the folate deficient HeLa cells than in the folate replete HeLa cells. 3HPGA or 3H methyl-THFA bound to the FABP of folate deficient sera, some uremic sera, human or cow's milk was less available for the uptake by the HeLa cells. The percent uptake of 3HPGA by HeLa cells was inversely related to the amount of FABP in several sera tested. FABP added to the culture medium following a 1 hr pulse of 3HPGA did not decrease the cellular uptake of 3HPGA. Evidence was found for an energy dependent, active mechanism for efflux of 3HPGA from the HeLa cell.

Original languageEnglish
Pages (from-to)760-764
Number of pages5
JournalExperimental Biology and Medicine
Volume147
Issue number3
DOIs
StatePublished - Dec 1974

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