Govoroun M, McMeel O M, D'Cotta H, Ricordel M J, Smith T, Fostier A, Guiguen Y
INRA (Institut National de la Recherche Agronomique), Campus de Beaulieu, 35042 Rennes Cedex, France.
J Exp Zool. 2001 Nov 1;290(6):558-66. doi: 10.1002/jez.1106.
In fish, according to Yamamoto's model, androgens would drive testis differentiation and estrogens ovarian differentiation. In order to study the implication of steroid enzymes in rainbow trout gonadal differentiation, we examined the expression of some steroid enzyme genes during natural differentiation (cholesterol side chain cleavage = P450scc, 17-hydroxylase/lyase = P450c17, 3beta-hydroxysteroid dehydrogenase = 3betaHSD) and androgen-induced differentiation (P450scc, P450c17, 3betaHSD, aromatase = P450aro, and 11beta-hydroxylase = P45011beta). Expressions of P450scc, 3betaHSD, and P450c17 were all detected in male and female gonads at 55 days post-fertilization (dpf), i.e., two weeks before histological differentiation. There were no differences in their expression level respective to the sex. The androgen treatment was carried out by administration of 11beta-hydroxyandrostenedione (11betaOHDelta4) in genetic all-female populations and the resulting sex ratios were found to be 100% male even at a low dosage of 1 mg/kg of food. Following 11betaOHDelta4 treatment, only the expression of P450c17 was found to be sustained when compared with the female untreated control. In contrast, P450scc was clearly up-regulated and 3betaHSD and P450aro down-regulated by the androgen treatment. P45011beta gene expression remained low in gonads of androgen-treated females, as it did in control untreated females. These results together demonstrate that steroidogenesis in rainbow trout is potentially active in pre-differentiating gonads of both sexes, and that one of the masculinizing actions of androgens in the species may be to down-regulate the female-specific gonadal P450aro gene expression. However, in vivo androgen treatment in genetic females does not induce the same pattern of steroid gene expression as in genetic males. These data suggest that exogenous androgens might induce a male differentiation process with P450aro inhibition being one of the steps required. However, this process would not involve endogenously produced 11-oxygenated androgens.
根据山本模型，在鱼类中，雄激素会促使睾丸分化，雌激素会促使卵巢分化。为了研究类固醇酶在虹鳟性腺分化中的作用，我们检测了自然分化过程中（胆固醇侧链裂解酶=P450scc、17-羟化酶/裂解酶=P450c17、3β-羟类固醇脱氢酶=3βHSD）以及雄激素诱导分化过程中（P450scc、P450c17、3βHSD、芳香化酶=P450aro和11β-羟化酶=P45011β）一些类固醇酶基因的表达。在受精后55天（dpf），即组织学分化前两周，在雄性和雌性性腺中均检测到P450scc、3βHSD和P450c17的表达。它们的表达水平在性别上没有差异。在遗传上全为雌性的群体中通过投喂11β-羟基雄烯二酮（11βOHΔ4）进行雄激素处理，结果发现即使在低剂量1毫克/千克食物的情况下，产生的性别比例也为100%雄性。在11βOHΔ4处理后，与未处理的雌性对照相比，仅发现P450c17的表达持续存在。相反，雄激素处理使P450scc明显上调，3βHSD和P450aro下调。在雄激素处理的雌性性腺中，P45011β基因表达与未处理的对照雌性一样仍然很低。这些结果共同表明，虹鳟的类固醇生成在两性性腺分化前可能是活跃的，并且该物种中雄激素的雄性化作用之一可能是下调雌性特异性性腺P450aro基因的表达。然而，对遗传雌性进行体内雄激素处理不会诱导出与遗传雄性相同的类固醇基因表达模式。这些数据表明，外源性雄激素可能通过抑制P450aro诱导雄性分化过程，而这是所需的步骤之一。然而，这个过程不涉及内源性产生的11-氧化雄激素。
