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5-Methyltetrahydrofolic Acid, 5-Formyltetrahydrofolic Acid (Folinic Acid), and Folic Acid Requirements of Normal and Rous Sarcoma Virus-infected Chicken Fibroblasts¹

Department of Pathology, University of Manitoba Faculty of Medicine, Winnipeg, Manitoba R3E OW3, Canada

Normal and Rous sarcoma virus-infected chicken fibroblasts proliferate maximally in a culture medium containing a physiological (10 ng/ml) concentration of 5-methyltetrahydrofolic acid or folinic acid (5-formyltetrahydrofolic acid), while their maximal proliferation requires a hyperphysiological (1000 ng/ml) concentration of folic acid. The normal and Rous-infected fibroblasts do not differ in their requirements for 5-methyltetrahydrofolate, folinic acid, or folic acid.

¹ Supported by grants from the Richardson Foundation and the National Cancer Institute of Canada.

² To whom requests for reprints should be addressed.

Received 5/16/78. Accepted 8/17/78.