Evolution des niveaux plasmatiques de la gonadotropine glycoprotéique et de la 17-alpha-hydroxy-20 beta-dihydroprogestérone au cours de la maturation et de l'ovulation chez la truite arc-en-ciel, Salmo gairdnerii

The plasma concentrations of the glycoproteic gonadotropin (GTH) and of the 17 alpha hydroxy-20 beta dihydroprogesterone (17 alpha 20 beta OHP) have been followed in the course of ovulation in 6 rainbow trout, using radioimmunoassays on samples taken every two days. A first slow and limited GTH increase (10 to 20 ng/ml) is detected before and during the ovulation, while the 17 alpha 20 beta OHP rises sharply (up to three to five hundreds nanogrammes per millilitre). Then the progestagen levels drop back to their previous values, for about three weeks after ovulation. At the same time, a second higher GTH increase (25 to 20 ng/ml) is taking place. The relations between these two hormones, maturation and ovulation are discusse

The modulatory effect in vitro of oestradiol-17β, testosterone or cortisol on the output of 17α-hydroxy-20β-dihydroprogesterone by rainbow trout (Salmo gairdneri) ovarian follicles stimulated by the maturational gonadotropin s-GtH

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Limites et améliorations du sexage des salmonidés par dosage de la 11-cétotestostérone circulante

National audienceThe use of plasma concentrations of 11-ketotestosterone for determining sex has been studied in various species of salmonids (O. kisutch, S. salar, S. gairdneri, S. trutta) at different stages of their sexual development. Radioimmunological titrations were performed; though they are less sensitive than filtrations with an extraction by organic solvents, they are quicker to use. The percentage of error in sex determination is low (5%) in animals that have developing gonads or that are still in prepuberty, but is much higher in immature animals. A single injection of total pituitary extract (equivalent to 100 ng of s-GtH per gram) will reduce this error to 2% by stimulating 11-ketotestosterone secretion.L'identification du sexe à partir de la mesure des concentrations plasmatiques de 11-cétotestostérone a été tentée chez différentes espèces de salmonidés (Oncorhynchus kisutch, Salmo salar, Salmo gairdneri, Salmo trutta) et à différents stades du développement sexuel. Un dosage radioimmunologique, moins sensible qu'un dosage comportant une extraction en phase organique, mais de mise en œuvre plus rapide, a pu être utilisé. Les pourcentages d'erreur de sexage chez les animaux dont les gonades se développent ou chez les animaux prépubères sont faibles (< 5%), alors qu'ils sont beaucoup plus importants chez les immatures. Une seule injection à de jeunes truitelles immatures d'un extrait hypophysaire total (équivalent à 100 ng de gonadotropine purifiée par gramme de poisson) permet, en stimulant la sécrétion de 11-cétotestostérone, de réduire cette erreur à 2%

The modulatory effect in vitro of oestradiol-17β, testosterone or cortisol on the output of 17α-hydroxy-20β-dihydroprogesterone by rainbow trout (Salmo gairdneri) ovarian follicles stimulated by the maturational gonadotropin s-GtH

International audienc