Regulation of Ovarian Steroidogenesis In Vitro by Follicle-Stimulating Hormone and Luteinizing Hormone During Sexual Maturation in Salmonid Fish1

Abstract

The regulation of ovarian steroidogenesis in vitro by coho salmon FSH and LH was investigated in intact coho salmon follicles and isolated follicular layers at various stages of oocyte maturation, from late vitellogenesis until the completion of germinal vesicle breakdown (GVBD). In granulosa layers from all stages, LH, but not FSH, stimulated 17alpha,20beta-dihydroxy-4-pregnen-3-one (17, 20beta-P) production. In theca-interstitial layers from all stages, FSH and LH stimulated steroid production, LH being more potent than FSH. The basal steroid output of intact follicles was significantly lower than that of isolated follicular layers, and their response to FSH and LH also differed. First, the intact follicles produced 17alpha-hydroxyprogesterone in response to FSH during the central germinal vesicle stage while theca-interstitial layers did not. Second, estradiol-17beta production was not inhibited by LH during final oocyte maturation in intact follicles, as observed for granulosa layers. Our results indicate that LH is the determining factor regulating the production of the maturation-inducing steroid, 17,20beta-P, and the induction of GVBD in the salmonid ovary. In summary, we have provided evidence for maturation-associated changes in the effects of FSH and LH in the salmonid ovary, which further supports the hypothesis that FSH and LH have distinct functions in the teleost ovary.

Oogenesis and plasma levels of sex steroids in cultured females of brown trout (Salmo trutta linnaeus, 1758) in Chile

“…The plasma concentrations remained close to basal levels throughout the study, increasing considerably only during ovulation. This pattern agrees with the pattern described in salmonid females for the progestagens (Nagahama '94, '97;Planas et al, 2000).…”

Biological activities of recombinant Manchurian trout FSH and LH: their receptor specificity, steroidogenic and vitellogenic potencies

“…As expected, both r-mtFSH and r-mtLH were capable of inducing T and E2 production in maturing ovarian follicles which are generally in agreement with the potency of purified FSH and LH in coho salmon (Planas et al 2000), although the magnitude of steroidogenic effect of coho salmon FSH and LH was greater than that of r-mtFSH and r-mtLH effects on the maturing follicles. In fully grown follicles from mature rainbow trout, on the other hand, r-mtFSH but not r-mtLH had a weak stimulatory effect on E2 production, whereas only r-mtLH stimulated the production of T at a dose of 100 ng/ml.…”

“…Despite differences in detailed steroidogenic potency, both FSH and LH stimulated in vitro production of estradiol-17b (E2) by vitellogenic ovarian tissues in chum salmon, Oncorhynchus keta (Suzuki et al 1988b), coho salmon, O. kisutch (Planas et al 2000), goldfish, Carassius auratus (Van Der Kraak et al 1992), red seabream, Pagrus major (Tanaka et al 1993), and tuna, Thunnus obesus (Okada et al 1994), and in vitro 11-ketotestosterone (11-KT) production by spermatogenic testicular tissue in coho salmon (Planas & Swanson 1995). In contrast, only LH stimulates in vitro production of the maturationinducing steroid, 17a,20b-dihydroxy-4-pregnen-3-one (DHP), by the mature follicles of salmonids (Suzuki et al 1988b, Planas et al 2000 and the induction of germinal vesicle breakdown in mature oocytes of red seabream (Kagawa et al 1998). However, data on unique function of FSH are limited to date, i.e.…”

Functional specificity of the rainbow trout (Oncorhynchus mykiss) gonadotropin receptors as assayed in a mammalian cell line

“…In contrast, LH is the major regulating factor of late gametogenesis during oocyte maturation and ovulation (Jalabert 1976). In salmonids, LH alone stimulates production of the maturation-inducing steroid in the granulosa cells (17,20b-dihydroxy-4-pregnen-3-one), thus inducing germinal vesicle breakdown (Planas et al 2000).…”