Janz D M, McMaster M E, Munkittrick K R, Van der Kraak G
Department of Zoology, University of Guelph, Ontario, Canada.
Toxicol Appl Pharmacol. 1997 Dec;147(2):391-8. doi: 10.1006/taap.1997.8283.
Exposure of feral fish populations to bleached kraft pulp mill effluent (BKME) results in a variety of negative impacts on reproductive fitness including reduced ovarian development, reduced egg size, decreased fecundity with age, delayed sexual maturation, and alterations in reproductive endocrine homeostasis at multiple sites along the pituitary-gonadal axis. The present study provides evidence of elevated apoptotic DNA fragmentation and increased expression of the 70-kDa heat shock protein (HSP70) in ovarian follicular cells from prespawning white sucker (Catostomus commersoni) exposed to BKME. Apoptosis is the molecular mechanism responsible for ovarian follicular atresia which is involved in various stages of vertebrate ovarian development such as follicular recruitment, growth, differentiation, and regression. In mammals, induction of HSP70 is associated with inhibition of hormone-sensitive steroidogenesis and mediation of luteal regression. The 3'-end labeling of isolated ovarian follicular cell DNA revealed a 10-fold increase in the extent of apoptosis in BKME-exposed white sucker in comparison to follicles collected from a nearby reference site. Western blotting for ovarian follicular HSP70 levels showed increased expression of this protein in fish exposed to BKME. The elevated ovarian cell apoptosis and increased HSP70 expression in BKME-exposed fish were associated with reduced ovary size, decreased plasma testosterone, and increased plasma 17 beta-estradiol concentrations, but not induction of hepatic ethoxyresorufin O-deethylase activity. It is not known whether increased ovarian HSP70 expression in BKME-exposed fish is related to elevated apoptosis or represents a general response to environmental stress. Since apoptosis is regulated by several hormonal factors and conserved gene products, these data suggest that certain components of BKME increase ovarian cell apoptosis in fish via stimulation of cell death signaling. However, it is unclear whether BKME stimulates ovarian cell apoptosis directly or if this response occurs secondarily as a result of altered reproductive endocrine homeostasis.
野生鱼类种群暴露于漂白硫酸盐制浆厂废水（BKME）会对生殖健康产生多种负面影响，包括卵巢发育受阻、卵尺寸减小、随着年龄增长繁殖力下降、性成熟延迟以及垂体-性腺轴多个部位生殖内分泌稳态的改变。本研究提供了证据，表明暴露于BKME的产卵前白亚口鱼（Catostomus commersoni）卵巢滤泡细胞中凋亡DNA片段化增加，且70 kDa热休克蛋白（HSP70）表达上调。细胞凋亡是导致卵巢滤泡闭锁的分子机制，其参与脊椎动物卵巢发育的各个阶段，如滤泡募集、生长、分化和退化。在哺乳动物中，HSP70的诱导与激素敏感性类固醇生成的抑制以及黄体退化的介导有关。对分离的卵巢滤泡细胞DNA进行3'端标记显示，与从附近参考位点采集的滤泡相比，暴露于BKME的白亚口鱼的凋亡程度增加了10倍。对卵巢滤泡HSP70水平进行的蛋白质印迹分析表明，暴露于BKME的鱼类中该蛋白的表达增加。暴露于BKME的鱼类中卵巢细胞凋亡增加和HSP70表达上调与卵巢大小减小、血浆睾酮降低以及血浆17β-雌二醇浓度升高有关，但与肝乙氧基异吩恶唑酮O-脱乙基酶活性的诱导无关。尚不清楚暴露于BKME的鱼类中卵巢HSP70表达增加是与凋亡增加有关，还是代表对环境应激的一般反应。由于细胞凋亡受多种激素因子和保守基因产物的调节，这些数据表明BKME的某些成分通过刺激细胞死亡信号通路增加鱼类卵巢细胞凋亡。然而，目前尚不清楚BKME是直接刺激卵巢细胞凋亡，还是这种反应是生殖内分泌稳态改变的继发结果。
