Evaluation of the pulmonary inhalation toxicity of diborane

本研究旨在阐明乙硼烷（B_2H_6，CAS：19287-45-7）对大鼠的亚急性肺和睾丸毒性。将雄性Wister大鼠暴露于0.11 ppm或0.96 ppm乙硼烷中8周，每天6小时，每周5天。对照组暴露于过滤空气中。取支气管肺泡灌洗液（BALF），进行血液学、生化学和组织病理学检查。观察附睾精子计数和精子形态学变化，睾丸组织病理学检查。BALF检查显示，在暴露于0.96 ppm的大鼠中，中性粒细胞的百分比以剂量依赖性方式增加，巨噬细胞的百分比减少。0.96ppm染毒组大鼠BALF中总磷脂和单个磷脂含量均增加。在暴露于0.96 ppm的大鼠中，磷脂酰甘油加鞘磷脂的比例降低，磷脂酰乙醇胺和磷脂酰肌醇增加。LDH在暴露于0.96 ppm的大鼠中增加，ALP显示出剂量依赖性增加。血清中α_1-抗胰蛋白酶和超氧化物歧化酶（SOD）活性在0.11或0.96ppm染毒组均升高。这些变化显示出对暴露于乙硼烷的大鼠肺的剂量依赖性影响，可能表明即使在暴露于0.11 ppm的大鼠中也发生了II型细胞增殖和/或肥大而无组织病理学变化的机能亢进。睾丸检查未发现特殊结果。乙硼烷（0.1ppm）的TLV-TWA（ACGIH，1991年）似乎很高，可能不安全，因为大鼠肺部8周内的无明显作用水平低于0.11ppm。ACGIH（1991年）建议的0.1 ppm TLV-TWA的现行职业接触限值似乎过于防止乙硼烷对可能反复接触乙硼烷的工人的影响。有必要仔细管理工作环境，以避免暴露于乙硼烷。

This study aimed to clarify the subacute pulmonary and testicular toxicity of diborane (B_2H_6, CAS : 19287-45-7) in rats. Male Wister rats were exposed for 8 weeks to 0.11 ppm pr 0.96 ppm of diborane for 6 hours/day, 5days/week. The control group wes exposed to filtered air. Bronchoalveolar lavage fluid (BALF), hematological, biochemical and histopathological examinations were conducted. Sperm counts and spermatic morphological changes were examined in epididymides, and histopathological examination was carried out in testes. BALF examinations revealed that the percentage of neutrophils increased in a dose-dependent manner and that of macrophages decreased in rats exposed to 0.96 ppm. Quantities of total and individual phospholipids in BALF increased in rats exposed to 0.96ppm. The proportion of phosphatidylglycerol plus sphingomyelin decreased, and phosphatidylethanolamine and phosphatidylinositol increased in rats exposed to 0.96 ppm. LDH increased in rats exposed to 0.96 ppm, and ALP showed a dose-dependent increase. In serum, alpha _1-antitrypsin and superoxide dismutase (SOD) activities increased in rats exposed to 0.11 or 0.96 ppm. These changes showed dose-dependent effects on the lung in rats exposed to diborane, possbly indicating that the hyperenergia of type II cells with proliferation and/or hypertrophy without histopathological changes occurred even in rats exposed to 0.11 ppm. Testicular examinations revealed no particular findings. The TLV-TWA of diborane (0.1ppm)(ACGIH 1991) seems to be high and possibly unsafe, considering that the no-observed-effect level over 8 weeks for rat lung was under 0.11 ppm. The current occupational exposure limit of 0.1 ppm TLV-TWA recommended by ACGIH (1991) seems to be too prevent the effects of diborane on workers who may be repeatedly exposed to diborane. It is necessary to manage the working environment carefully in order to avoid exposure to diborane.