[Kinetics of the development of the glucocorticoid effect on the thymus in adrenalectomized rats]

It was shown that the kinetics of distribution of cortisol and the synthetic glucocorticoid triamcinolone acetonide in the subcellular fractions of rat thymus after a single injection of subphysiological doses of the hormones is identical. Extraction of the nuclear fraction by 0.4 and 2 M NaCl did not reveal any differences in the mode of the hormone interactions with the nuclear acceptor sites. A single injection of triamcinolone acetonide resulted in inhibition of the precursor incorporation into DNA after 8 hours. This effect was dependent on the type and concentration of the precursor as well as on the steroid dose. The inhibiting effect of glucocorticoids is a specific one; progesterone injected under identical conditions did not affect the precursor incorporation into DNA. The inhibition of thymidine incorporation into DNA was paralleled with a drop in the thymidine kinase activity in thymus cytosol. The inhibiting effect of triamcinolone acetonide on thymidine incorporation into thymus DNA is not due to the changes in the trapping and intracellular pool of thymidine phosphates.