Body retention and tissue distribution of a 51chromium (Cr) tracer were studied in thyroparathyroidectomized (TPTX) rats and in TPTX rats after replacement with thyroxin, calcitonin, or parathyroid hormone. A tracer dose containing 1 ng Cr or less and 0.5 to 0.7 muCi of high specific activity 51Cr (Cr III) was injected intravenously in control, TPTX, and TPTX animals receiving hormone replacement. Three days later, the 51Cr content of the serum and various tissues was determined and the data were expressed as percent dose per milliliter or gram and as tissue: serum 51Cr ratios. TPTX resulted in a significant increase in total body 51Cr retention and 40 to 240% increases in serum and tissue 51Cr levels. Tissue:serum 51Cr ratios were uniformly depressed. Replacement with thyroxin completely or partially reversed these changes in all tissues studied except bone. Calcitonin and parathyroid hormone had no consistent effect on body, serum, or tissue 51Cr levels. These data, indicating that 51Cr distribution is influenced by thyroid hormone activity but not by calcitonin or parathyroid hormone, are compatible with the hypothesis that thyroid hormone controls cellular Cr transport.

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The effect of LH and FSH on radiovanadium ("V) metabolism in testis was explored by administering LH and/or FSH daily to hypophysectomized (HYPOX) rats prior to and after 48V injection. Seven and fourteen days after 48V injection, the animals were counted in a whole body gamma counter, sacrificed, and serum and tissue samples taken for weighing and counting. Whole body, serum, and tissue contents of 48V of HYPOX rats were not affected by LH or FSH except in testis. In testis, there were both independent and additive effects of LH and FSH on testicular weight and 48V content, expressed as either content per gram or per organ. LH was more active than FSH. The usual fourfold increase in 48V content per gram seen in HYPOX testis was reduced 50% by LH + FSH. On an organ basis, 48V content was increased 50-100% by LH + FSH compared to either HYPOX or intact rats. These data demonstrate that gonadotropins affect the 48V content of the testes in HYPOX rats in the absence of growth hormone, adrenal steroids, and thyroxine. Whether these data indicate a direct effect of vanadium in reproductive physiology or are secondary to nonspecific trophic or other effects on the testis remain to be determined. 349 0037-9727/80/100349-05$0 1 .OO/O