Biosynthese des steroides

Par contre, les dérivés 7a-hydroxylés de la PREG et de la DHEA déclenchent une production accrue d'IgG lorsqu'ils sont administrés au même moment que le lysozyme. La quantité la plus faible injectée (6,25 mg/kg) est la plus active (tableau 1). L'injection dans ces conditions de 50 mg/kg de 7ss-hydroxy-DHEA donne une réponse identique à celle de lg/kg de DHEA administrée 1 heure avant celle du lysozyme (tableau 1). Les dérivés 7-hydroxylés de 1'ADIOL ne déterminent, à la dose testée, qu'une très faible augmentation des IgG anti-lysozyme sériques (tableau 1).

In vitro steroid biosynthesis in the male and female gonad of Mytilus edulis was investigated. Using tritium and 14 C-labeled precursors, four enzyme systems were demonstrated: a 3β-hydroxysteroid dehydrogenase-Δ 5,4 -isomerase comples (pregnenolone→progesterone; 17α-hydroxypregnenolone→17α-hydroxyprogesterone; dehydroepiandrosterone→androstenedione), a C 17,20 -lyase (17α-hydroxypregnenolone→dehydroepiandrosterone; 17α-hydroxyprogesterone→androstenedione), a 17β-hydroxysteroid dehydrogenase (dehydroepiandrosterone→androstenediol; androstenedioneαtestosterone; estradiol-17βαestrone) and a 5α-reductase (testosterone→5α-dihydrotestosterone). The yields were very low (–1%) except when estrogens were used (10–50%). Radioimmunoassay techniques indicate the presence of testosterone and possibly estrogens in the gonad of the mussel at two different stages in its gametogenic cycle.

Growth hormone (GH) and anabolic androgenic steroids (AAS) are commonly used in sports communities. Several studies have suggested an association between GH and AAS. We have investigated the impact of GH in rats treated with nandrolone decanoate (ND). Male Wistar rats received ND (15 mg/kg) every third day during three weeks and were subsequently treated with recombinant human GH ( U/kg) for ten consecutive days. Plasma samples were collected and peripheral organs (. heart, liver, testis and thymus) were dissected and weighed. Concentration of thirteen endogenous steroids was measured in the rat plasma samples using high specificity LC-MS/MS methods. Seven steroids were detected and quantified, and concentrations of estrone, testosterone, and androstenedione were significantly different among the groups, while concentrations of pregnenolone, DHEA, 17-hydroxyprogesterone and corticosterone were not altered. Administration of rhGH alone altered the plasma steroid distribution, and the results demonstrated significantly increased concentrations of plasma estrone as well as decreased concentrations of testosterone and androstenedione in the ND-treated rats. Administration of rhGH to ND-pretreated rats did not reverse the alteration of the steroid distribution induced by ND. Administration of ND decreased the weight of the thymus, and addition of rhGH did not reverse this reduction. However, rhGH administration induced an enlargement of thymus. Taken together, the plasma steroid profile differed in the four groups, . control, AAS, rhGH and the combination of AAS and rhGH treatment.

Biosynthese des steroides

biosynthese des steroides


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