The Effect of Glucocorticoids on Protein and Nucleic Acid Synthesis in Mouse Fibroblasts Growing in Vitro

Glucocorticoids which depress the rate of growth of mouse fibroblasts in vitro decrease the rate of thymidine and uridine incorporation into macromolecular material. The effect is seen as early as 6 hours after addition of the steroid to the culture medium, and concentrations of steroids as low as 10-9 m (6α,9α-difluoro-11β, 16α, 17α, 21-tetrahydroxy-1, 4-pregnadiene-3, 20-dione 16,17-acetonide) to 10-7 m (cortisol) are effective. Deoxyribonucleic acid synthesis is depressed earlier and to a greater degree than ribonucleic acid synthesis. Protein synthesis is not depressed within the first 24 hours after steroid addition. The locus of the biochemical effect of the steroid seems to be at the stage of the DNA-dependent polymerization of the deoxyribonucleoside triphosphates into DNA.