Seasonal changes in plasma cortisol, testosterone and oestradiol-17β in the plaice, Pleuronectes platessa L

Sexual patterns of monooxygenase function in the liver of marine teleosts and the regulation of activity by estradiol

“…Therefore, plasma E~levels L in female winter flounder collected in November were probably below peak physiological levels. There does not appear to be information on the cycle of plasma E 2 levels in winter flounder, but in plaice, a closely related species, E 2 concentrations peaked at 162 ± 10 ng/ml in pre-spawning females (Wingfield and Grimm, 1977), This maximum was close to the range of plasma E 2 in group I, the winter flounder dosed with only 1 mg/kg E 2 (35-156 ng/ml).…”

“…In mature female teleosts, including flounder, testosterone levels are elevated as this hormone is the precursor for both E 2 and the major androgen ll-ketotestosterone Wingfield and Grimm, 1977). In studies of brook trout and killifish, E 2 injections were associated with elevated plasma testosterone Stegeman, Singh et al, unpublished).…”

“…As the prespawning stage in fish corresponds to peak serum titers of sex steroids (Campbell et al, 1975;Wingfield and Grimm, 1977;Lambert et al, 1978), this suggested that steroids could be regulating xenobiotic metabolism. Because of the sex differences in the specific content of P-450, rates of monooxygenase activities per nmol P-450 (i .e., the turnover values) did not always demonstrate the same sex pattern as the specific activity (see Table 1-3l.…”

Croissance ovocytaire et régulation stéroïdienne chez les poissons à pontes unique et multiples : une revue

“…Ce type de profil bimodal de l'E2 est également observé chez d'autres espèces, comme chez le poisson-chat, Ictalurus nebulosus LeSueur (Burke et al 1984), la dorade royale, Spams aurata L. (Kadmon et al 1985), le Morone americana Gmelin. (Jackson & Sullivan 1985) A la fin du cycle sexuel, principalement avant la maturation finale et l'ovulation, la concentration en oestrogènes chute (Wingfield & Grimm 1977, MacGregor et al 1981, Singh & Singh 1990). Ce déclin réduit la rétroaction négative qu'exercent les hormones stéroï-diennes sur l'hypothalamus et l'hypophyse et permet une décharge ovulatoire de GtHU (Fostier et al 1983).…”

Metabolic effects of C21 steroids in female Epinephelus akaara (Teleostei: Serranidae)

“…Les (Jalabert, 1976;Jalabert et al, 1977;Goetz and Theofan, 1979;Duffey and Goetz, 1980;lwamatsu, 1980 (Jalabert, 1976) and Heteropneustes fossilis (Sundararaj, 1979). Cortisol level has also been demonstrated to increase with sexual maturation (Wingfield and Grimm, 1977;Cook et al, 1980). The increase in corticosteroids in some species at the end of the sexual cycle has been associated with spawning migration, which requires energy (McBride et al, 1986).…”