11β-HYDROXY DEHYDROGENASE SYSTEM ACTIVITY IN THYMI OF MICE FOLLOWING PROLONGED CORTISOL TREATMENT

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Abstract
The purpose of these studies was to compare the amount of transformation of cortisol to cortisone produced by lymphocytes of untreated animals and those of animals treated with large doses of cortisol for a period of several days. The lymphatic organs (spleens, lymph nodes and thymi) of 50 mice of the CBA strain which were given cortisol acetate (1 mg.) daily for 9 days were compared to untreated CBA mice of the same age and sex for the capacities of these cells to transform cortisol to cortisone. The amounts of differences of ll[beta]-hydroxydehydrogenase system activity present in the two groups of animals were estimated by incubating equivalent amounts of tissue (300 mg.) from each of the two groups with cortisol -4C14 (11.5 m[mu]M). In untreated animals the abilities of the tissues to make the transformation were highest in lymph nodes, second highest in spleen and very low in the thymus. Following prolonged treatment with large doses of cortisol it was found that the thymus increased its capacity to transform cortisol to cortisone by 217%. Lymph nodes showed a small but definite increase and there was a slight decrease in the spleen. The factors which might be brought into play to explain this enormous increase in thymic activity are discussed.