Effects of Cortisol on the Incorporation of Thymidine-2-l4C Into Nucleic Acids of Lymphatic Tissue from Adrenalectomized CBA Mice

Abstract

CBA male mice 10-14 weeks of age were adrenalectomized and, 24 hr later, injected with various doses of cortisol acetate. Each dose, i.e., 10, 50, 100, 250, 500 and 750 μg of cortisol acetate, was injected into a group of 15 animals, and the carrier solution of carboxymethylcellulose was used to inject 15 controls. Six hr after cortisol administration, the mice were injected with 1 μc thymidine-2-¹⁴C and then weighed. Thirty min after thymidine administration, they were sacrificed, and their spleens, thymi and lymph nodes were removed and weighed. These lymphatic tissues were extracted for nucleic acids. Total amounts of DNA and RNA were measured with colorimetric procedures, and the amount of thymidine- 2-¹⁴C incorporation was measured in a liquid scintillation spectrometer. Decreases in organ weights occurred with increasing doses of cortisol acetate. In addition, DNA synthesis, measured as dpm/mg DNA, decreased significantly with increasing doses of cortisol acetate. The maximum decrease in dpm/mg DNA occurred after a dose of 250 ng of cortisol acetate in the thymi, lymph nodes and spleen. (Endocrinology76: 1100, 1965)