Holmes M, Suarez J D, Roberts N L, Mole M L, Murr A S, Klinefelter G R
Department of Chemistry, North Carolina Central University, Durham, USA.
J Androl. 2001 Sep-Oct;22(5):878-90.
Dibromoacetic acid (DBA) is a by-product of drinking water disinfection that alters spermatogenesis in adult male rats. To identify a mechanism by which DBA alters spermatogenesis, seminiferous tubules representing specific groups of spermatogenic stages were exposed either in vivo or in vitro, and structural and functional consequences were evaluated. Seminiferous tubules representing stages I-V, VI-VIII, and IX-XIV were isolated from testes of adult rats and cultured overnight in conditions of reduced oxygen and temperature. For in vivo exposures, seminiferous tubules were recovered from animals that had received 250 mg/kg DBA via gavage for 5 days. For in vitro exposures, 180 and 600 microM concentrations were tested; these concentrations bracket the concentration of DBA observed within the testis following in vivo exposure. Protein synthesis was evaluated by 35S-methionine labeling overnight and quantitative analysis of radiolabeled proteins in mini, 2-dimensional (2D) sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels. Radio-inert cultures were processed for light and electron microscopy. Morphologicaf evaluation indicated that all spermatogenic stages of the seminiferous tubules from control animals were well maintained during the isolation and culture period. Although no treatment-related lesions were observed following in vivo exposure, histological alterations were observed at the lowest in vitro exposure. There was a significant diminution (P < .05) in the synthesis of 4 cytosolic proteins following both in vivo and in vitro exposures. Diminution in these proteins was restricted to stages I-V and IX-XIV of spermatogenesis, suggesting that proteins involved in the early stages of spermiogenesis are uniquely sensitive to DBA exposure. Because histology and protein synthesis were affected by relevant in vitro exposures, this indicates that DBA is capable of altering spermatogenesis directly.
二溴乙酸（DBA）是饮用水消毒的副产物，可改变成年雄性大鼠的精子发生过程。为了确定DBA改变精子发生的机制，将代表特定生精阶段组的生精小管在体内或体外进行暴露，并评估其结构和功能后果。从成年大鼠睾丸中分离出代表第I - V期、VI - VIII期和IX - XIV期的生精小管，并在降低氧气和温度的条件下培养过夜。对于体内暴露，从经口灌胃给予250 mg/kg DBA 5天的动物中回收生精小管。对于体外暴露，测试了180和600 microM的浓度；这些浓度涵盖了体内暴露后在睾丸中观察到的DBA浓度。通过35S - 甲硫氨酸过夜标记和在小型二维（2D）十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳凝胶中对放射性标记蛋白质进行定量分析来评估蛋白质合成。对无放射性的培养物进行光镜和电镜检查。形态学评估表明，对照动物生精小管的所有生精阶段在分离和培养期间都得到了良好维持。虽然体内暴露后未观察到与处理相关的病变，但在最低体外暴露时观察到了组织学改变。体内和体外暴露后，4种细胞溶质蛋白的合成均显著减少（P < 0.05）。这些蛋白质的减少仅限于精子发生的第I - V期和IX - XIV期，表明参与精子形成早期阶段的蛋白质对DBA暴露具有独特的敏感性。由于组织学和蛋白质合成受到相关体外暴露的影响，这表明DBA能够直接改变精子发生。
