Early Localization of125I-Labeled Human Growth Hormone in Adrenals and Other Organs of Immature Hypophysectomized Rats

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Abstract
Human growth hormone (HGH) labeled with 125I was injected intravenously into hypophysectomized, immature rats. One rat was frozen 6 min and another 20 min after injection by immersion in hexane cooled with dry ice. Whole-body sections were made of the frozen rats and autoradiograms were prepared by placing these sections on x-ray film. The autoradiograms revealed that, at both time intervals after injection, there was a high concentration of radioactive material in the kidney, liver and adrenal cortex. The only other tissues found to have a higher radioactive density than that of blood were the submandibular glands, nasal mucosa, gastric mucosa, bone and follicles of vibrissae. The radioactivity in the adrenal cortex was slightly higher in the zona glomerulosa than in the zona fasciculata and it was lowest in the zona reticularis. The concentration in the epiphyseal plates was no higher than that in bone or soft tissues. The radioactivity in the submandibular gland had the electrophoretic mobility of growth hormone and not free iodide. The distribution in 8 organs of 131I-albumin was compared with that of 125I-HGH at 6 and 20 min by removal of the organs and direct isotope counting. The distributions substantiated the specific localizations of HGH seen in the autoradiograms. Pretreatment of the rats with ACTH or HGH 6 min before administering the 125I-HGH altered the concentration of 12BI-HGH in kidney, liver and adrenals. (Endocrinology88: 1309, 1971)

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