STIMULATION OF MITOSIS IN ADULT MICE BY ADMINISTRATION OF THYMIDINE

Abstract

Mitotic activity of the duodenal epithelium of adult male mice has been examined at intervals up to six hours after subcutaneous adminstration of 10 [mu]g of normal thymidine or of 8.5 g (12.5 [mu]c) of tritiated thymidine. A comparison to saline-injected control animals has revealed an immediate and highly significant increase in the number of metaphase figures in the experimental animals, which was maintained throughout the six -hour period of observation and averaged 29.2 per cent during this period. Consideration of the mechanisms which might be involved in thymidine action in vivo suggests that the results represent a physiological, rather than toxic, action and that the addition of free thymidine at this dose level in vivo shortens the average DNA synthesis time in duodenal epithelium and so permits an increase in the rate of cell entry into mitosis.