Localisation of 3H-corticosterone inside thymocytes at different stages of ontogenetic development.

The thymocytes of newborn rats incorporated considerably greater amounts of labeled corticosterone in culture than those of two or four weeks old rats. The incorporation of label tended to increase up to 5 min of exposure in all age groups, but did not further increase in any during longer exposures. The hormone entered the nucleus of the thymocytes and assumed primarily a heterochromatic localisation.