RADIOACTIVE COMPOUNDS IN THE URINE OF RATS AFTER ADMINISTRATION OF LABELLED CORTICOTROPHIN

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Abstract
Male rats (Wistar) weighing 150-200 g were divided into 4 groups of 5 rats each. All groups were injected intravenously with corticotropin-I131, and the urethra of each animal was ligated after injection. The groups were killed at 7, 20, 60 and 120 min. after injection, and the total radioactivity of the thyroid, kidneys and bladder with contents was measured. One-dimensional paper chromatograms were made from urine using a phenol-water system or a butanol-dioxane-ammonia system. The radioactivity of the kidney showed a significant decrease in the 1 hr. group as compared to the 7 and 20 min. groups. Paper chromatography of the urine indicated that both iodide and other I131 compounds are excreted into the urine, and the amount of urinary radiocorticotropin is very small, as no spot with the same Rf value as corticotropin could be found in the phenol-water system. The main metabolic path for corticotropin in the kidney is the reexcretion of it or its metabolites into the bloodstream.