Maturation-associated changes in the response of the salmon testis to the steroidogenic actions of gonadotropins (GTH I and GTH II) in vitro

Abstract

Previous studies from our laboratory have shown that salmon gonadotropins GTH I and GTH II have similar effects on testicular steroidogenesis in vitro. To determine whether the relative potencies of GTH I and GTH II changed during late stages of spermatogenesis, the effects of GTH I and GTH II on in vitro steroid production by testicular tissue from fish in stages IV to V of spermatogenesis were examined. Fragments of testicular tissue were incubated with GTH I and GTH II for 18 h at 15 degrees C. The in vitro production of 11-ketotestosterone (11-KT), testosterone (T), 17 alpha-hydroxyprogesterone (17OH-P), and 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) was determined by RIA. GTH I and GTH II were equipotent in stimulating the production of 11-KT, T, and 17,20 beta-P (17OH-P was not detectable) by testicular tissue in stage IV of spermatogenesis. The sensitivity of testicular tissue to the steroidogenic effects of GTH II increased as spermatogenesis progressed. In contrast, the sensitivity of testicular tissue to the effects of GTH I on 17,20 beta-P production declined from stages IV to V, while the sensitivity of testicular tissue to the effects of GTH I on 11-KT production remained unchanged. These changes in sensitivity to GTH I and II are consistent with previously reported changes in GTH receptors in salmon testis and support the hypothesis that GTH I and GTH II may have different roles during spermatogenesis.

Changes in mRNAs encoding steroidogenic acute regulatory protein, steroidogenic enzymes and receptors for gonadotropins during spermatogenesis in rainbow trout testes

“…For salmon testis in vitro, the relative potencies of FSH and LH in stimulating steroid synthesis did not change before the late spermatogenesis stage and spermiation (Planas & Swanson 1995). However, during the later stages of spermatogenesis and spermiation, the sensitivity of the testis to the steroidogenic effects of LH on progestogen production increased, whereas the sensitivity of the testis to the effects of FSH decreased (Planas & Swanson 1995). These results imply that the differences in the steroidogenic actions of FSH and LH that are associated with particular stages of gonadal development are probably due to changes in expression of genes encoding their receptors.…”

“…In male rainbow trout, FSH in plasma was elevated during mid-spermatogenesis, whereas LH showed a significant increase in plasma during the spermiating stage (Prat et al 1996, Gomez et al 1999. For salmon testis in vitro, the relative potencies of FSH and LH in stimulating steroid synthesis did not change before the late spermatogenesis stage and spermiation (Planas & Swanson 1995). However, during the later stages of spermatogenesis and spermiation, the sensitivity of the testis to the steroidogenic effects of LH on progestogen production increased, whereas the sensitivity of the testis to the effects of FSH decreased (Planas & Swanson 1995).…”

Plasma testosterone and 11-ketotestosterone levels of male pacu Piaractus mesopotamicus (Cypriniformes, Characidae)

“…Spermatogenesis and spermiation have been considered to be under gonadotropin control in teleosts (4,13). In male teleost fish the major androgens synthesized by the testes appear to be testosterone and 11-ketotestosterone (4,6,8,14).…”

17,20β-P and cortisol are the main in vitro metabolites of 17-hydroxy-progesterone produced by spermiating testes of Micropogonias furnieri (Desmarest, 1823) (Perciformes: Sciaenidae)

“…Furthermore, during the complete testicular cycle, Lh or Fsh can stimulate 17,20β-P both in vivo and in vitro, but Lh stimulation is greater during the late testes development phases (Le Gac & Loir, 1988;Schulz & Blüm, 1990;Schulz et al, 1992;Planas et al, 1993;Planas & Swanson, 1995;Vizziano & Le Gac, 1998). These results suggest that 17,20β-P mediates the late phases of testes development.…”