Yamada Tomoya, Kunimatsu Takeshi, Miyata Kaori, Yabushita Setsuko, Sukata Tokuo, Kawamura Satoshi, Seki Takaki, Okuno Yasuyoshi, Mikami Nobuyoshi
Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd., 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-8558, Japan.
Toxicol Sci. 2004 May;79(1):64-74. doi: 10.1093/toxsci/kfh093. Epub 2004 Feb 19.
Development of an internationally recognized standard for the Hershberger assay as a screening tool to detect potential (anti-)androgenic chemicals is in progress. In the present preliminary study, we evaluated the reliability of the enhanced Hershberger assay to detect thyroid hormone modulating activity, while concentrating attention on possible confounding influence on evaluation of (anti-)androgenic activity. Castrated or testosterone propionate (TP; 0.2 or 0.25 mg/kg/day)-injected castrated male Crj:CD(SD) IGS rats (seven weeks of age) were dosed for 10 days by oral gavage with vehicle (corn oil) or the following chemicals: propylthiouracil (PTU; 2.5 mg/kg/day), a potent inhibitor of thyroid hormone synthesis, phenobarbital (PB; 125 mg/kg/day) and 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE; 100 mg/kg/day), two hepatic enzyme inducers that enhance the clearance of thyroid hormones. PTU markedly increased thyroid weights, and decreased serum T3 and T4, and increased serum TSH, also causing marked microscopic alteration of the thyroid gland. In comparison, PB and p,p'-DDE only significantly affect serum T4 and revealed some histopathological findings. The alterations appeared to be more robust in the presence of TP. Furthermore, data for p,p'-DDE demonstrated its anti-androgenic effects, whereas PTU and PB had little or no effects on the weights of androgen-related accessory glands/tissues: the ventral prostate, dorso-lateral prostate, seminal vesicles with coagulating glands, glans penis, Cowper's glands, and levator ani plus bulbocavernosus (LABC) muscles. Weight of the LABC muscles was decreased by PB treatment in TP-treated castrated rats. These findings in the present study suggests that the enhanced Hershberger assay, with evaluation of thyroid histopathology and weights, and hormone levels, appears to be reliable for screening for not only (anti-)androgenic chemicals but also thyroid hormone modulators. In order to evaluate whether the sensitivity and specificity of such a thyroid assay is great enough for routine screening purposes, future experiments including dose-response studies using lower dose levels have to be performed.
作为一种检测潜在（抗）雄激素化学物质的筛查工具，正在制定一项国际认可的赫什伯格试验标准。在本初步研究中，我们评估了增强型赫什伯格试验检测甲状腺激素调节活性的可靠性，同时关注对（抗）雄激素活性评估可能产生的混杂影响。对去势的或注射丙酸睾酮（TP；0.2或0.25毫克/千克/天）的去势雄性Crj:CD(SD) IGS大鼠（7周龄），通过口服灌胃给予赋形剂（玉米油）或以下化学物质，持续给药10天：丙硫氧嘧啶（PTU；2.5毫克/千克/天），一种强效甲状腺激素合成抑制剂；苯巴比妥（PB；125毫克/千克/天）和2,2-双（4-氯苯基）-1,1-二氯乙烯（p,p'-DDE；100毫克/千克/天），两种可增强甲状腺激素清除率的肝酶诱导剂。PTU显著增加甲状腺重量，降低血清T3和T4，并增加血清TSH，还导致甲状腺明显的微观改变。相比之下，PB和p,p'-DDE仅显著影响血清T4，并显示出一些组织病理学发现。在TP存在的情况下，这些改变似乎更明显。此外，p,p'-DDE的数据证明了其抗雄激素作用，而PTU和PB对雄激素相关附属腺体/组织的重量几乎没有影响：腹侧前列腺、背外侧前列腺、带有凝固腺的精囊、阴茎头、考珀氏腺以及提肛肌加球海绵体肌（LABC）。在TP处理的去势大鼠中，PB处理使LABC肌肉重量降低。本研究中的这些发现表明，通过评估甲状腺组织病理学、重量和激素水平，增强型赫什伯格试验似乎不仅对（抗）雄激素化学物质，而且对甲状腺激素调节剂的筛查都是可靠的。为了评估这种甲状腺试验的敏感性和特异性是否足以用于常规筛查目的，必须进行包括使用较低剂量水平的剂量反应研究在内的未来实验。
