关键词：雌激素；曝光（生理学）；激素;大鼠
摘 要：NTO was administered to male (0, 250, and 500 mg/kg-day) and female (0, 500, and 1000 mg/kg-day) Sprague-Dawley rats (15/sex/group) via oral gavage from weaning through puberty. Animals were examined daily for onset of puberty. Estrous cyclicity was evaluated daily upon completion of vaginal opening (VO). Age and body weight at VO and PPS, and all measures of estrous cyclicity were not affected by treatment with NTO. Testis mass was reduced by 30% and 65% compared to control in the 250 and 500 mg/kg-day groups, respectively. The reduction in testis mass was associated with tubular degeneration/atrophy. Less pronounced reductions in the mass of androgen-dependent accessory reproductive tissues were also observed in the 500 mg/kg-day group; however, the reduction was only significant in the epididymides. There were no differences in hormone levels or thyroid follicle and colloid scores between NTO treatment groups and the control groups. These findings suggest that NTO is not acting as an estrogen or thyroid active compound, but may indicate effects on steroidogenesis and/or direct testicular toxicity.