This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Pak, T. R. Articles by Tsai, P.-S. Search for Related Content PubMed PubMed Citation Articles by Pak, T. R. Articles by Tsai, P.-S.

Testosterone and Estrogen Act via Different Pathways to Inhibit Puberty in the Male Siberian Hamster (Phodopus sungorus)

Department of Environmental, Population and Organismic Biology, University of Colorado, Boulder, Colorado 80309

Address all correspondence and requests for reprints to: Toni R. Pak, Department of Environmental, Population and Organismic Biology, University of Colorado, Campus Box 334, Boulder Colorado 80309. E-mail: toni.pak{at}colorado.edu

The peripubertal transition in male mammals is accompanied by a gradual decrease in sensitivity to the inhibitory effects exerted by gonadal hormones, such as T and E2. Here, we investigated the effects of chronic T and its metabolites, 5-dihydrotestosterone and E2 on the hypothalamo-pituitary-gonadal axis at puberty. We also examined if T effects are distinct or mediated through its conversion to 5-dihydrotestosterone or E2. Twenty-day-old male Siberian hamsters were sc implanted with a SILASTIC brand capsule containing varying doses of T, 5-dihydrotestosterone, or E2. Several functional parameters of the hypothalamo-pituitary-gonadal axis were evaluated including hypothalamic GnRH concentration, pituitary and plasma FSH levels, pituitary FSH and LH mRNA, and testicular status. Our results showed that gonadal steroids inhibited puberty in a dose-dependent manner as evaluated by testes mass (undiluted steroid: T, 27 ± 3 mg; 5-dihydrotestosterone, 18 ± 1 mg; and E2, 62 ± 4 mg relative to cholesterol-implanted controls, 510 ± 42 mg). Also, T decreased plasma FSH below detectable levels, but pituitary FSH concentration was unaffected (1.37 ± 0.16 ng/µg protein) while E2-treated hamsters had normal plasma FSH levels (3.5 ± 0.98 ng/ml) yet significantly lower pituitary FSH concentration (0.09 ± 0.04 ng/µg protein). These results showed that the pathways of T and E2 action on the hypothalamo-pituitary-gonadal axis are distinct.

This article has been cited by other articles:

				S. J Meachem, S. Schlatt, S. M Ruwanpura, and P. G Stanton The effect of testosterone, dihydrotestosterone and oestradiol on the re-initiation of spermatogenesis in the adult photoinhibited Djungarian hamster J. Endocrinol., March 1, 2007; 192(3): 553 - 561. [Abstract] [Full Text] [PDF]

				P.-S. Tsai, S. M. Moenter, H. R. Postigo, M. El Majdoubi, T. R. Pak, J. C. Gill, S. Paruthiyil, S. Werner, and R. I. Weiner Targeted Expression of a Dominant-Negative Fibroblast Growth Factor (FGF) Receptor in Gonadotropin-Releasing Hormone (GnRH) Neurons Reduces FGF Responsiveness and the Size of GnRH Neuronal Population Mol. Endocrinol., January 1, 2005; 19(1): 225 - 236. [Abstract] [Full Text] [PDF]

				T. S. McMullin, M. E. Andersen, A. Nagahara, T. D. Lund, T. Pak, R. J. Handa, and W. H. Hanneman Evidence That Atrazine and Diaminochlorotriazine Inhibit the Estrogen/Progesterone Induced Surge of Luteinizing Hormone in Female Sprague-Dawley Rats Without Changing Estrogen Receptor Action Toxicol. Sci., June 1, 2004; 79(2): 278 - 286. [Abstract] [Full Text] [PDF]

				B. T. Akingbemi, C. M. Sottas, A. I. Koulova, G. R. Klinefelter, and M. P. Hardy Inhibition of Testicular Steroidogenesis by the Xenoestrogen Bisphenol A Is Associated with Reduced Pituitary Luteinizing Hormone Secretion and Decreased Steroidogenic Enzyme Gene Expression in Rat Leydig Cells Endocrinology, February 1, 2004; 145(2): 592 - 603. [Abstract] [Full Text] [PDF]

				T. R. Pak, G. R. Lynch, D. M. Ziegler, J. B. Lunden, and P.-S. Tsai Disruption of pubertal onset by exogenous testosterone and estrogen in two species of rodents Am J Physiol Endocrinol Metab, January 1, 2003; 284(1): E206 - E212. [Abstract] [Full Text] [PDF]

				T. R. Pak, G. R. Lynch, and P.-S. Tsai Differential Alteration of the Reproductive Axis by Testosterone and Estrogen in Peripubertal and Adult Male Siberian Hamsters (Phodopus sungorus) Biol Reprod, September 1, 2002; 67(3): 706 - 711. [Abstract] [Full Text] [PDF]