Norman D. Lee

Studies of Radioactive Insulin

Highly purified crystalline insulin was labeled (and hereinafter noted as insulin* ) by iodination with radioactive iodine (I), presumably on the tyrosine rings, by the method of Ferrebee et al. The material was hypoglycemic to rabbits and assayed according to prediction by the rat diaphragm-glucose uptake technic. The radioactivity stayed with the protein fraction in trichloracetic acid precipitation, in dialysis and in chromatography, and had the same mobility as unlabeled insulin in paper electrophoresis. Therefore the label did not alter certain measurable properties of the insulin. Distribution studies in the rat fifteen minutes after intravenous administration of insulin* showed the greatest concentration to be in the renal cortex. Thyroid (presumably largely free I), liver and stomach also showed concentrations higher than plasma. Muscle concentration was not striking but total muscle mass was such that 30 to 50 per cent of the material was in that locus. Brain showed a notably low concentration, and red blood cells none at all. There was very little in the urine. It concentrated in the placenta and a small amount entered the fetus. A small but significant fraction was absorbed into the blood when insulin* was injected into the small intestine. Studies of the subcellular fractions of liver, kidney and muscle showed that insulin* had entered the cell. It was distributed in the cytostructural elements of the liver in a characteristic manner and fixation on the subcellular particles was shown to depend on cellular

Prompt Effect of Adrenal Stimulation on the Free Amino Acid Content of Rat Tissues

Summary The effect within 2 hours of adrenocorticotropin and adrenal hormone administration on the free amino acid content of rat tissues was determined. Liver and kidney showed a significant increase following administration of either hormone preparation and the adrenals showed an increase following adrenocorticotropin administration.

Role of Triiodothyronine-I131 Purity in T-3 Tests

Summary Using a standard thyrodiagnostic test based on in vitro partitioning of triiodothyronine-I131 between plasma proteins and erythrocytes of whole blood, results were found to differ depending on the commercial source of labeled triiodothyronine. Chromatographic study showed these preparations to be heterogeneous. Impurities were occasionally present in fresh materials and developed in significant proportions during the accepted usable life of the preparation.

Factors contributing to the difference in propylthiouracil goitrogenesis in rats and guinea pigs.

Summary and Conclusions (1) The difference between the rat and guinea pig with respect to thiouracil goitrogenesis was investigated using the binding of I131 to surviving thyroid slices as a measure of thyroid hormone production. (2) Propylthiouracil in concentrations ranging from 10-7 M through 10-5 M inhibited hormone synthesis to an equal extent in both rat and guinea pig thyroid slices. In vivo studies have indicated the compound to concentrate in the gland to a comparable degree in both species. On the other hand, in the absence of propylthiouracil, hormone synthesis in rat thyroid slices occurred at 5 times the rate for guinea pig thyroid slices. (3) In view of these observations it is suggested that the species difference in thiouracil goitrogenesis can be accounted for by differences in the rates of peripheral utilization of circulating thyroid hormone.