Khan I A, Mathews S, Okuzawa K, Kagawa H, Thomas P
The University of Texas at Austin, Marine Science Institute, 750 Channelview Drive, 78373, Port Aransas, TX, USA.
Comp Biochem Physiol B Biochem Mol Biol. 2001 Jun;129(2-3):251-9. doi: 10.1016/s1096-4959(01)00318-9.
Exposure of Atlantic croaker (Micropogonias undulatus) to the polychlorinated biphenyl mixture (Aroclor 1254, PCB; 1 mg/kg body wt/day for 30 days) during the early-recrudescence phase of the gonadal cycle results in the impairment of LH secretion and gonadal growth. In order to determine whether impairment was due to disruption of the stimulatory GnRH neuroendocrine pathway, we compared various parameters of the GnRH-LH system in early recrudescing vs. spermiating (mature) fish. Seabream GnRH (GnRH) content in the preoptic anterior hypothalamic area (POAH) and pituitary, pituitary GnRH receptor concentrations, and basal and GnRH analog (GnRHa)-induced LH secretion were significantly higher in gonadally mature croaker compared to early-recrudescing fish. In a subsequent experiment, the effects of PCB on the same neuroendocrine indices were investigated during the gonadal recrudescence phase of croaker. PCB exposure during the period of testicular maturation prevented the natural increase in GnRH content in the POAH but not in the pituitary. This finding suggests that PCB may impair GnRH synthesis in the POAH. The number of pituitary GnRH receptors also remained significantly lower in the PCB-exposed group, which was likely due to an impairment of GnRH release. The GnRH content in the POAH, number of pituitary GnRH receptors, and LH secretion in the PCB-exposed group were comparable to those in early-recrudescing fish, suggesting an impairment of normal maturation of the GnRH-LH system during the gonadal recrudescence phase. This impairment may be due to a direct action of PCB on GnRH neurons and/or indirectly via interference with other neurotransmitter pathways that modulate GnRH function.
在性腺周期的早期恢复期，将大西洋鳎（Micropogonias undulatus）暴露于多氯联苯混合物（氯丹1254，PCB；1毫克/千克体重/天，持续30天）会导致促黄体生成素（LH）分泌受损以及性腺生长受影响。为了确定这种损害是否是由于刺激性促性腺激素释放激素（GnRH）神经内分泌途径的破坏，我们比较了早期恢复期与排精期（成熟）鱼类GnRH-LH系统的各种参数。与早期恢复期的鱼类相比，性腺成熟的鳎鱼视前区下丘脑前部（POAH）和垂体中的鲷鱼GnRH（GnRH）含量、垂体GnRH受体浓度以及基础和GnRH类似物（GnRHa）诱导的LH分泌显著更高。在随后的实验中，研究了PCB在鳎鱼性腺恢复期对相同神经内分泌指标的影响。在睾丸成熟期间暴露于PCB可阻止POAH中GnRH含量的自然增加，但垂体中则不然。这一发现表明，PCB可能损害POAH中GnRH的合成。暴露于PCB的组中垂体GnRH受体的数量也仍然显著较低，这可能是由于GnRH释放受损所致。暴露于PCB的组中POAH中的GnRH含量、垂体GnRH受体数量和LH分泌与早期恢复期的鱼类相当，这表明在性腺恢复期GnRH-LH系统的正常成熟受到损害。这种损害可能是由于PCB对GnRH神经元的直接作用和/或通过干扰调节GnRH功能的其他神经递质途径间接导致的。
