Author
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Wise, Thomas |
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Submitted to: The Journal of Steroid Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/2/1998 Publication Date: N/A Citation: N/A Interpretive Summary: The thymus gland makes chemicals called hormones that affect reproduction, growth, and health of animals. An understanding of how the thymus is regulated and how it interacts with target organs will ultimately lead to improved domestic animal production. Studies were conducted to determine effects of a thymic hormone, thymulin, on gonadal function of rats. Testosterone was increased with injection of thymulin. Regulatory aspects of the immune system extend beyond the general health of animals and may have important roles in maintaining gonadal function and reproductive capability. Such information indicates thymic hormones play an important role in growth, health, and reproduction; understanding regulation may improve animal production. Technical Abstract: Numerous immuno-peptides have now been shown to have positive or negative effects on steroidogenic function of the gonads, but few have been tested in vivo. Thymulin, a nine amino acid secretory peptide of the thymus, was incubated with rat testis and with hCG to monitor the thymulin augmentation of hCG stimulation of testosterone synthesis and estrone. At 3 wk of age, thymulin decreased testosterone and estrone synthesis with testicular incubations. At 6 and 9 wk of age, thymulin stimulated testosterone and estrone synthesis. High doses of thymulin (100 ng/ml) inhibited steroid synthesis. No thymulin augmentation of hCG-stimulated testosterone synthesis was noted in vitro. In pituitary-intact rats, thymulin injected into the jugular vein depressed testosterone and estrone concentrations. In hypophysectomized rats, thymulin had no effect on testosterone synthesis. In hCG-primed hypophysectomized rats, thymulin injection was followed by significant increases in testosterone concentrations. Increases in testicular steroidogenesis from thymulin required gonadotropin, and increased levels of thymulin had inhibitory effects on gonadal steroidogenesis. |
