Faber Willem D, Roberts Linda S G, Stump Donald G, Tardif Robert, Krishnan Kannan, Tort Maria, Dimond Stephen, Dutton Dave, Moran Elizabeth, Lawrence Wade
Victor, New York 14564, USA.
Birth Defects Res B Dev Reprod Toxicol. 2006 Feb;77(1):10-21. doi: 10.1002/bdrb.20063.
This study was conducted to evaluate the potential adverse effects of ethylbenzene (EB) on reproductive capability from whole-body inhalation exposure of F0 and F1 parental animals.
Four groups of Crl:CD(SD)IGS BR rats (30/sex/group for F0 and 25/sex/group for F1) were exposed to 0, 25, 100, and 500 ppm EB for 6 hr/day for at least 70 consecutive days before mating. Inhalation exposure for the F0 and F1 females continued throughout mating, gestation through gestation day (GD) 20, and lactation days (LD) 5-21. On LD 1-4, females received EB in corn oil via oral gavage at dose levels of 26, 90, and 342 mg/kg/day (divided into three equal doses, approximately 2 hr apart), as calculated from a physiologically-based pharmacokinetic (PBPK) model to provide similar maternal blood area-under-concentration (AUC) as provided by inhalation. Pups were weaned on postnatal day (PND) 21 and exposure of the F1 generation started on PND 22. Estimates of internal exposure were determined by measuring EB concentrations in blood collected from F1 dams (4/group) and their culled pups 1 hr after the last gavage dose on PND 4. On PND 22, blood was collected from these same F1 dams and their weanlings for EB analysis 1 hr after a 6-hr inhalation exposure. The remainder of the F2 generation was not directly exposed.
EB exposure did not affect survival or clinical observations. Male rats in the 500 ppm group in both generations gained weight more slowly than the controls. There were no indications of adverse effects on reproductive performance in either generation. Male and female mating and fertility indices, pre-coital intervals, spermatogenic endpoints, ovarian follicle counts, reproductive organ weights, lengths of estrous cycle and gestation, live litter size, pup weights, developmental landmarks, and postnatal survival were unaffected. No adverse exposure-related macroscopic pathology was noted at any level.
Increased liver weights were found in the animals exposed to 500 ppm. F1 maternal whole blood EB concentrations of 0.49, 3.51, or 18.28 mg/L were found 1 hr after administration of a composite oral dose of 26, 90, or 342 mg/kg/day, respectively, but no detectable EB was found in blood samples of their F2 PND 4 culled pups. F1 maternal mean whole blood EB levels 1 hr after a 6-hr inhalation exposure on postpartum day (PPD) 22 was 0.11 mg/L (25 ppm), 0.56 mg/L (100 ppm), and 11 mg/L (500 ppm). For the offspring exposed with their dams on PND 22, F2 pup blood EB concentrations ranged from 0.017-0.039 mg/L (25 ppm), 0.165-0.465 mg/L (100 ppm), and 8.82-15.74 mg/L (500 ppm). Because decreased weight gain in the 500 ppm males was transient and no histopathological changes were associated with the increased liver weights in the 500 ppm male and female groups, these changes were not considered adverse. Therefore, for parental systemic toxicity, 100 ppm was considered a NOEL and 500 ppm a NOAEL in this study. The 500 ppm exposure concentration was considered a NOAEL for F0 and F1 reproductive toxicity and offspring developmental endpoints.
本研究旨在评估乙苯（EB）经全身吸入暴露于F0和F1亲代动物后对生殖能力的潜在不良影响。
将四组Crl:CD(SD)IGS BR大鼠（F0代每组雌雄各30只，F1代每组雌雄各25只）在交配前连续至少70天每天暴露于0、25、100和500 ppm的EB中6小时。F0和F1代雌性大鼠在整个交配、妊娠直至妊娠第20天（GD20）以及哺乳期第5至21天（LD5 - 21）均持续进行吸入暴露。在哺乳期第1至4天，雌性大鼠通过口服灌胃给予玉米油中的EB，剂量水平分别为26、90和342 mg/kg/天（分为三等份剂量，间隔约2小时），这是根据基于生理的药代动力学（PBPK）模型计算得出的，以提供与吸入暴露相似的母体血药浓度 - 时间曲线下面积（AUC）。幼崽在出生后第21天（PND21）断奶，F1代的暴露从PND22开始。通过测量PND4最后一次灌胃剂量后1小时从F1代母鼠（每组4只）及其被淘汰幼崽采集的血液中的EB浓度来确定体内暴露估计值。在PND22，对这些相同的F1代母鼠及其断奶幼崽在6小时吸入暴露后1小时采集血液进行EB分析。F2代的其余部分未直接暴露。
EB暴露不影响生存率或临床观察结果。两代中500 ppm组的雄性大鼠体重增长比对照组慢。两代中均未发现对生殖性能有不良影响的迹象。雄性和雌性的交配和生育指数、交配前间隔、生精终点、卵巢卵泡计数、生殖器官重量、发情周期和妊娠期长度、活产仔数、幼崽体重、发育标志以及出生后存活率均未受影响。在任何暴露水平均未观察到与暴露相关的宏观病理学不良变化。
发现暴露于500 ppm的动物肝脏重量增加。在分别给予26、90或342 mg/kg/天的复合口服剂量后1小时，F1代母鼠全血EB浓度分别为0.49、3.51或18.28 mg/L，但在其F2代PND4被淘汰幼崽的血液样本中未检测到EB。产后第22天（PPD22）6小时吸入暴露后1小时，F1代母鼠全血EB平均水平为0.11 mg/L（25 ppm）、0.56 mg/L（100 ppm）和11 mg/L（500 ppm）。对于在PND22与母鼠一同暴露的后代，F2代幼崽血液EB浓度范围为0.017 - 0.039 mg/L（25 ppm）、0.165 - 0.465 mg/L（100 ppm）和8.82 - 15.74 mg/L（500 ppm）。由于500 ppm雄性大鼠体重增加减少是短暂的，并且500 ppm雄性和雌性组肝脏重量增加未伴有组织病理学变化，这些变化不被视为不良影响。因此，对于亲代全身毒性，本研究中100 ppm被视为未观察到有害作用水平（NOEL），500 ppm被视为未观察到不良反应水平（NOAEL）。500 ppm的暴露浓度被视为F0和F1代生殖毒性以及后代发育终点的NOAEL。
