Polypeptide hormone receptors in vivo: demonstration of insulin binding to adrenal gland and gastrointestinal epithelium by quantitative radioautography.

A tissue-screening survey employing quantitative radioautography was carried out at 2 min after the intravascular injection of 125I-insulin into laboratory rats. The results revealed a substantial binding of insulin to cells forming the proximal convoluted tubule in kidney, hepatocytes of liver, acinar cells of the pancreas, parenchymal cells of the adrenal cortex and medulla, and epithelial cells of the gastrointestinal tract. Control experiments indicated that this binding was due to a specific interaction with the insulin receptor, except in the case of kidney where the binding was shown to be nonspecific. Although the major target for insulin action (liver) clearly demonstrated specific insulin binding, several other classical targets (adipocytes, skeletal, cardiac, and smooth muscle cells) showed no specific 125I-insulin binding and therefore indicated the limits of sensitivity of the in vivo radioautographic method. Nevertheless, the working hypothesis of a direct correlation of insulin receptor density with insulin action points to the hitherto unemphasized targets of pancreas, adrenal gland, and gastrointestinal tract as major sites of insulin action in the body.

Localization of H-2 antigens on mouse trophoblast cells.

The presence of H-2 antigens of the paternal and maternal haplotypes on mouse trophoblast cells was examined at several stages of pregnancy by using a sensitive immunolabeling technique followed by quantitative radioautography. Results revealed the presence of H-2 antigens (determined by the K or D loci) of both parental haplotypes on the F1 trophoblast cells. At 14-16 d of gestation, the antigen density was equivalent to that on adult thymocytes and there was a further 50% increase on day 18. H-2 antigens of both parental haplotypes are also found to be expressed on 11-13 d trophoblast cells.

A simplified method of emulsion coating and development for quantitative electron microscopic radioautography

IntroductionSeveral methods of mounting emulsion for radioautography at the electron microscopic level have been reported. From the viewpoint of quantitative radioautography, however, there are many critical problems in the procedure to produce radioautographs. For example, it is necessary to apply and develop emulsions in several experimental groups under an identical condition. Moreover, it is necessary to treat a lot of grids at the same time in the dark room for statistical analysis. Since the complicated process and technical difficulties in these procedures are inadequate to conduct a quantitative analysis of many radioautographs at once, many factors may bring about unexpected results. In order to improve these complicated procedures, a simplified dropping method for mass production of radioautographs under an identical condition was previously reported. However, this procedure was not completely satisfactory from the viewpoint of emulsion homogeneity. This paper reports another improved procedure employing wire loops.