Limitations in the Use of Carbon-Labeled and Tritium-Labeled Thymidine in Cell Culture Studies

Abstract

C14-thymidine or unlabeled thymidine was added to HeLa S3 cell cultures growing in Eagle''s medium. Thymidine in the culture medium causes a concentration-dependent inhibition of growth, with significant effects at levels as low as 10 [mu]g/ml. Thymidine in the medium reduces the incorporation of H3-uridine into both DNA and RNA. The effect on incorporation into RNA is unexpectedly great. Other nucleosides, added singly or together to the medium, cause effects similar to those induced by thymidine. Thirty-minute incubation with tritiated thymidine, (0.02 to 2.5 [mu]c/ml) and at 2 specific activities, did not affect the production of colonies of HeLa S3 cultures.