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Heterodimers and Homodimers of Inhibin Subunits Have Different Paracrine Action in the Modulation of Luteinizing Hormone-Stimulated Androgen Biosynthesis
Aaron J. W. Hsueh, Kristine D. Dahl, Joan Vaughan, Ermelinda Tucker, Jean Rivier, C. Wayne Bardin and Wylie Vale
Proceedings of the National Academy of Sciences of the United States of America
Vol. 84, No. 14 (Jul. 15, 1987), pp. 5082-5086
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/30334
Page Count: 5
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Inhibin, a gonadal hormone capable of preferential suppression of pituitary follicle-stimulating hormone (FSH) secretion, has recently been purified. The major form of this protein is an α β heterodimer encoded by two separate genes. In contrast to the FSH-suppressing action of the α β heterodimer, the β β homodimer stimulates FSH secretion. Luteinizing hormone (LH)-secreting pituitary cells and gonadal androgen-producing cells have long been shown to form a closed-loop feedback axis. Based on recent studies demonstrating the FSH stimulation of inhibin biosynthesis by ovarian granulosa and testis Sertoli cells, an additional closed-loop feedback axis exists between pituitary FSH- and gonadal inhibin-producing cells. Because uncharacterized Sertoli cell factors have been suggested to either stimulate or inhibit androgen production by testicular Leydig cells, we have tested the intragonadal paracrine actions of heterodimers and homodimers of inhibin subunits. In primary cultures of testis cells, the α β heterodimer of inhibin enhances Leydig cell androgen biosynthesis stimulated by LH, whereas the β β homodimer suppresses androgen production. Furthermore, similar modulatory actions of inhibin-related proteins were found in cultured ovarian theca-interstitial cells and theca explants treated with LH. In contrast, treatment with the inhibin-related proteins alone did not affect gonadal steroidogenesis. Our data indicate that the inhibin-related gene products synthesized by Sertoli and granulosa cells may form heterodimers or homodimers to serve as intragonadal paracrine signals in the modulation of LH-stimulated androgen biosynthesis and allow cross-communication between the two feedback loops.
Proceedings of the National Academy of Sciences of the United States of America © 1987 National Academy of Sciences