Ku W W, Chapin R E, Moseman R F, Brink R E, Pierce K D, Adams K Y
Developmental and Reproductive Toxicology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
Toxicol Appl Pharmacol. 1991 Oct;111(1):145-51. doi: 10.1016/0041-008x(91)90143-3.
Boric acid (H3BO3), an inorganic acid with widespread commercial use and consumer exposure, impairs fertility in male rodents at dose levels lower than those required to cause other adverse effects. Previous studies found a testicular lesion in adult Fischer rats fed 9000 ppm boric acid (1575 ppm boron) and slightly reduced basal serum testosterone levels. A CNS-mediated hormonal component to this lesion was suggested. Detailed data on the tissue disposition of boron in the rat, including accessory sex organs and the brain, are lacking. This study examined the tissue disposition of boron in reproductive, accessory sex organs, and other selected tissues in adult male Fischer rats fed 9000 ppm boric acid to determine if selective accumulation of boron in reproductive tissues, accessory sex organs, and/or the brain might correlate with and explain the apparent selective testicular toxicity. Adult male Fischer rats were fed 9000 ppm boric acid for up to 7 days. Animals were killed at 1, 2, 3, 4, and 7 days after the start of exposure. Plasma and excised tissues were heat-digested in acid and analyzed for boron by inductively coupled argon plasma emission spectrometry (ICAP). With the exception of adrenal glands, control boron levels in all tissues examined were below 4 micrograms/g. There was a rapid increase in plasma and tissue boron 1 day after the start of exposure (range 2- to 20-fold), with the exception of adipose tissue. With the exception of bone and adipose tissue, all soft tissues examined, including the testis, epididymis, accessory sex organs, hypothalamus, and rest of brain, appeared to reach steady-state boron levels (range 12-30 micrograms/g) by 3-4 days. Bone boron levels continued to increase up to the termination at 7 days (40-50 micrograms/g by Day 7). Bone attained the greatest concentration of boron (2- to 3-fold over plasma levels) while levels in adipose tissue were 20% of plasma levels during the 7-day exposure period. All other tissues appeared to show no appreciable accumulation of boron over plasma levels. The data suggest that neither the apparent selective testicular toxicity nor the slight CNS hormonal effect associated with boric acid exposure can be explained on the basis of selective accumulation of boron in the testis or brain/hypothalamus, respectively. Thus, the testicular toxicity is likely the result of certain biological processes that are unique to the testis and which are targets of boron exposure.
硼酸（H3BO3）是一种具有广泛商业用途且会接触到消费者的无机酸，在低于导致其他不良反应所需剂量的情况下，会损害雄性啮齿动物的生育能力。先前的研究发现，给成年Fischer大鼠喂食9000 ppm硼酸（1575 ppm硼）会导致睾丸损伤，并使基础血清睾酮水平略有降低。有人提出这种损伤存在中枢神经系统介导的激素成分。目前缺乏关于硼在大鼠体内组织分布的详细数据，包括附属生殖器官和大脑。本研究检测了喂食9000 ppm硼酸的成年雄性Fischer大鼠生殖组织、附属生殖器官及其他选定组织中硼的组织分布情况，以确定硼在生殖组织、附属生殖器官和/或大脑中的选择性积累是否可能与明显的选择性睾丸毒性相关并对其作出解释。成年雄性Fischer大鼠喂食9000 ppm硼酸长达7天。在开始接触后的第1、2、3、4和7天处死动物。将血浆和切除的组织在酸中进行热消解，并通过电感耦合氩等离子体发射光谱法（ICAP）分析硼含量。除肾上腺外，所有检测组织中的对照硼水平均低于4微克/克。接触开始后1天，血浆和组织中的硼含量迅速增加（范围为2至20倍），脂肪组织除外。除骨骼和脂肪组织外，所有检测的软组织，包括睾丸、附睾、附属生殖器官、下丘脑和大脑其他部分，到3至4天时似乎都达到了硼的稳态水平（范围为12至30微克/克）。骨骼中的硼含量在7天处死时持续增加（第7天达到40至50微克/克）。在7天的接触期内，骨骼中硼的浓度最高（比血浆水平高2至3倍），而脂肪组织中的硼含量为血浆水平的20%。所有其他组织似乎并未显示出硼在血浆水平之上有明显积累。数据表明，与硼酸接触相关的明显选择性睾丸毒性和轻微的中枢神经系统激素效应，分别不能基于硼在睾丸或大脑/下丘脑中的选择性积累来解释。因此，睾丸毒性可能是睾丸特有的某些生物学过程的结果，而这些过程是硼接触的靶点。
