Effect of cortisol on the release and retention of labelled DNA in the thymus and spleen of mice.

The lymphocytolytic effect of different doses of cortisol was studied in the thymus and spleen of mice previously injected with 3H-thymidine. The results indicate that in thymus the fraction of labelled cells was more resistant to cortisol than the unlabelled cell population. The release of DNA into the fraction of DNA soluble in 0.14 M NaC1 was delayed suggesting that cortisol controls indirectly the lymphocytolytic process. Up to 24 hours after administration of cortisol the loss of labelled spleen cells significantly exceeded the loss of unlabelled cells. The time course of the release of labelled DNA into the fraction of DNA soluble in 0.14 M NaC1 indicates that a fraction of labelled DNA was rapidly removed from the spleen after injection of cortisol.