Publikationsdatum:
2013-10-19
Beschreibung:
Thyroid hormones participate in regulating growth and homeostatic processes in vertebrates, including development and adult functioning of the reproductive system. Here we report a new stimulatory role of thyroid hormone on the proliferation of Sertoli cells (SCs) and single, type A undifferentiated spermatogonia (A und ) in adult zebrafish testes. A role for T 3 in zebrafish testis is suggested by in situ hybridization studies, which localized thyroid receptor α ( thr α) in SCs and the β ( thr β) mRNA in Sertoli and Leydig cells. Using a primary zebrafish testis tissue culture system, the effect of T 3 on steroid release, spermatogenesis, and the expression of selected genes was evaluated. Basal steroid release and Leydig cell gene expression did not change in response to T 3 . However, in the presence of FSH, T 3 potentiated gonadotropin-stimulated androgen release as well as androgen receptor ( ar ) and 17α-hydroxylase/17,20 lyase ( cyp17a1 ) gene expression. Moreover, T 3 alone stimulated the proliferation of both SCs and A und , potentially resulting in newly formed spermatogonial cysts. Additional tissue culture studies demonstrated that Igf3, a new, gonad-specific member of the IGF family, mediated the stimulatory effect of T 3 on the proliferation of A und and SCs. Finally, T 3 induced changes in connexin 43 mRNA levels in the testis, a known T 3 -responsive gene. Taken together, our studies suggest that T 3 expands the population of SCs and A und involving Igf signaling and potentiates gonadotropin-stimulated testicular androgen production as well as androgen sensitivity.
Print ISSN:
0013-7227
Thema:
Medizin
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