Berg A H, Westerlund L, Olsson P E
Department of Molecular Biology, Umeå University, SE- 901 87 Umeå, Sweden.
Gen Comp Endocrinol. 2004 Feb;135(3):276-85. doi: 10.1016/j.ygcen.2003.10.004.
Estrogens induce both vitellogenin (Vtg) and egg shell (zona pellucida; ZP) protein synthesis in salmonids. However, while Vtg is strictly under estrogenic control, recent reports suggest that additional mechanisms are involved in ZP protein synthesis. During sexual maturation both estrogen and glucocorticoid levels increase in the circulation of female fish. As glucocorticoids have been shown to interfere with Vtg induction in fish we investigated whether cortisol (F) had similar effects on ZP regulation. In the present study we determined both the natural variation in Vtg and ZP during an annual reproductive cycle in female Arctic char (Salvelinus alpinus), and the effect of co-treatment of juvenile Arctic char with 17beta-estradiol (E2) and F. During sexual maturation the expression of Vtg and ZP correlated to plasma levels of E2 and F. Determination of Vtg and ZP protein levels following co-treatment with E2 and F showed that F antagonized E2 induction of Vtg. However, F was observed to potentiate the expression of ZP protein in the same fish. These results indicate that in Arctic char Vtg and ZP proteins are not regulated by the same mechanisms and suggest that ZP protein expression does not necessarily imply exposure to estrogenic compounds alone, and may thus not be ideally suited as a biomarker of exposure to estrogenic compounds.
雌激素可诱导鲑科鱼类合成卵黄蛋白原（Vtg）和卵壳（透明带；ZP）蛋白。然而，虽然Vtg严格受雌激素控制，但最近的报告表明，ZP蛋白合成涉及其他机制。在性成熟过程中，雌性鱼类循环中的雌激素和糖皮质激素水平都会升高。由于糖皮质激素已被证明会干扰鱼类中Vtg的诱导，我们研究了皮质醇（F）对ZP调节是否有类似影响。在本研究中，我们确定了雌性北极红点鲑（Salvelinus alpinus）在年度繁殖周期中Vtg和ZP的自然变化，以及用17β-雌二醇（E2）和F共同处理幼年北极红点鲑的效果。在性成熟过程中，Vtg和ZP的表达与E2和F的血浆水平相关。用E2和F共同处理后测定Vtg和ZP蛋白水平表明，F拮抗E2对Vtg的诱导。然而，观察到F可增强同一条鱼中ZP蛋白的表达。这些结果表明，在北极红点鲑中，Vtg和ZP蛋白不受相同机制调节，并表明ZP蛋白表达不一定仅意味着暴露于雌激素化合物，因此可能不太适合作为暴露于雌激素化合物的生物标志物。
