Endocrine regulation of sperm release in an anuran amphibian Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/xg94hs66t

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  • The endocrine mechanisms involved in the initiation of sperm release from the vertebrate testis have not been elucidated. A seasonally breeding anuran amphibian, Hyla regilla, was selected as a model for testing the hypothesis that steroid action is involved in gonadotropin-stimulated sperm release. Experiments were carried out in vivo and in vitro utilizing three steroid inhibitors: 1) Flutamide, a nonsteroidal androgen receptor inhibitor, 2) CI-628, an estrogen receptor inhibitor, and 3) Cytadren, an arotnatase inhibitor. The rationale for using these drugs was to test the effect of steroid inhibition on sperm release from LH-stimulated testes. In vivo, Flutamide significantly inhibited sperm release compared to controls, by reducing the number of sperm released. CI-628 and Cytadren tended to increase the number of sperm released. In in vitro experiments excised testes were incubated in a Kreb's Ringers solution, prescreened for sperm, and then LH or LH and inhibitors were added. After incubation with the drugs, the number of sperm released into the medium were counted using a hemacytometer. The results of several experiments indicated that Flutamide treatment increased the incidence of total inhibition of sperm release. Further insight into the effect of Flutamide was gained by comparing sperm release of contralateral testes. Again, Flutamide significantly inhibited sperm release primarily by total inhibition, but also by reducing the number of sperm released by testes that responded. Preliminary results from the in vitro experiments using CI-628 and Cytadren tended to show a paradoxical response. In some cases these drugs inhibit the release of sperm while in other cases they stimulate sperm release. In addition, experiments were carried out in vitro using contralateral controls to test the effects of various steroids on sperm release. In these experiments, E₂, estrone, estriol, progesterone, T, DHT and corticosterone had no sperm-releasing effect. A low dose of DHT when given in conjunction with LH tended to increase the number of sperm released. A high dose of DHT plus LH, however, significantly inhibited sperm release. This study provides evidence for the hypothesis that steroids are involved in gonadotropin-stimulated spermiation. In particular, it is suggested that androgens may mediate the action of LH on the testis during the release of sperm. Estrogens also may be involved in spermiation either directly or indirectly, by regulating androgen biosynthesis. The particular roles of estrogen and androgens in the regulation of testicular function need further study.
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  • File scanned at 300 ppi (Monochrome) using ScandAll PRO 1.8.1 on a Fi-6670 in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
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