Collaborative work on evaluation of ovarian toxicity. 9) Effects of 2- or 4-week repeated dose studies and fertility study of di(2-ethylhexyl)adipate (DEHA) in female rats.
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The present study was designed to confirm whether or not the ovarian toxicity of di(2-ethylhexyl)adipate (DEHA), which is known to have effects on female fertility, could be evaluated by the new method of histopathological examination of the ovaries in repeated dose toxicity. DEHA was orally administered to Crl:CD(SD) female rats at the doses of 0, 200, 1,000 and 2,000 mg/kg for 2 or 4 weeks in repeated dose toxicity study and for 2 weeks before mating, throughout mating and until Gestation Days 7 in female fertility. In the repeated dose toxicity studies, increase in atresia of large follicle, decrease in currently formed corpus luteum and follicular cyst were observed in the 1,000 mg/kg and above groups, suggesting that DEHA disturbed ovulation and large follicle growth. In the fertility study, a significant increase in mean estrus cycle length and post-implantation loss rate were observed in the 1,000 mg/kg and above groups, and a significant decrease in implantation rate and number of live embryos and a significant increase in pre-implantation loss rate were observed in the 2,000 mg/kg group. The histopathological changes of ovary observed in the repeated dose toxicity studies were correlated with the result that DEHA affected the estrus cycle in the female fertility study. In conclusion, a 2-week administration period is sufficient for detection of the ovarian toxicities following treatment with DEHA by new histopathological examination of the ovaries. (+info)
Collaborative work on evaluation of ovarian toxicity. 10) Two- or four-week repeated dose studies and fertility study of di-(2-ethylhexyl) phthalate (DEHP) in female rats.
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The main purpose of this collaborative work is to determine the optimal administration period required to detect toxic effects in evaluation of ovarian morphological changes in repeated-dose toxicity studies. To assess the morphological and functional changes induced in the ovaries by di-(2-ethylhexyl) phthalate (DEHP), two repeated-dose toxicity studies (repeated dose for 2 or 4 weeks) of DEHP administrated to female rats at dose levels of 0, 300, 1,000 and 3,000 mg/kg were conducted in collaboration with a female fertility study at the same dosages from 2 weeks prior to mating to Day 7 of pregnancy. Histopathology of the ovaries in both repeated-dose toxicity studies showed vacuolation of stromal cells in the groups receiving 300 mg/kg or more and an increase of large atretic follicles in groups at 1,000 mg/kg or more. In the 4-week study, a decrease in new corpora lutea was observed in the 3,000 mg/kg group. In the female fertility study, the 3,000 mg/kg group showed prolongation of the mean estrous cycle and irregular estrous cycles. Cesarean section revealed a decrease of pregnancy rate in the 3,000 mg/kg group. No effects on fertility or early embryonic development were found in groups at 1,000 mg/kg or less. These findings indicate that histopathological changes in the ovary are important endpoints for the evaluation of drugs which induce ovarian damage. In conclusion, for a repeated-dose toxicity study, a 2-week administration period is sufficient to detect ovarian toxicity caused by DEHP. (+info)
Collaborative work on evaluation of ovarian toxicity. 11) Two- or four-week repeated-dose studies and fertility study of ethylene glycol monomethyl ether in female rats.
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The objective of this study was to determine the optimal period of administration for detection of ovarian toxicity in rat repeated-dose toxicity studies. A well-known ovarian toxicant, ethylene glycol monomethyl ether (EGME), was administered to female rats at dose levels of 0, 30, 100, or 300 mg/kg for 2 or 4 weeks (repeated-dose toxicity studies). The same doses were administered to female rats for 2 weeks prior to mating, during mating, and until Day 6 of pregnancy (fertility study). In the repeated-dose toxicity studies, continuous diestrus was observed at > or = 100 mg/kg regardless of period of administration. The alterations of ovarian morphology observed at > or = 100 mg/kg after 2 or 4 weeks of administration were characterized by hypertrophy of the corpora lutea with decreased cellular debris indicating apoptosis, and increased proliferating cell nuclear antigen (PCNA)-negative large atretic follicles. The finding that newly-formed basophilic corpora lutea were scarce in affected animals exhibiting continuous diestrus suggested suppression of ovulation due to hypertrophic corpora lutea. In the fertility study, irregular estrous cycles, prolonged mating periods, lower pregnancy rates and decreased corpora lutea of pregnancy were observed at > or = 100 mg/kg. The irregularities of estrous cycle observed in some animals at 30 mg/kg were minimal. The ovarian histopathological changes in repeated-dose toxicity studies correlated well with impairment of female fertility found in the fertility study. It is concluded that a repeated-dose toxicity study with a treatment period for 2 weeks or longer is sufficient for evaluation of ovarian toxicity induced by EGME. (+info)
Collaborative work on evaluation of ovarian toxicity. 12) Effects of 2- or 4-week repeated dose studies and fertility study of indomethacin in female rats.
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2-week and 4-week general toxicity studies of indomethacin, a nonselective inhibitor of cyclooxygenase 1 and 2, were performed using rats. A female fertility study was also conducted to compare the results to those of ovarian histopathological findings. The main purposes of the present studies are to assess whether a precise histopathological examination, taking the morphological changes the female reproductive organs undergo during each estrus phases into account, can evaluate toxicity to the ovaries, and to determine the optimal administration period for detecting ovarian toxicity. Indomethacin was administered on a daily basis to female Sprague-Dawley rats at doses of 0, 0.4, 1.3, or 4 mg/kg in the both the general toxicity studies and the female fertility study. In the general toxicity studies, unruptured follicles or luteinized cysts were observed histopathologically in the 4 mg/kg group in both the 2-week and 4-week studies. In addition, follicular cysts were found in the 4 mg/kg group in the 4-week study. Estrous cyclicity was not disturbed in both studies. There were no histopathological changes in the ovaries of the 1.3 mg/kg group in general toxicity studies. In the female fertility study, no toxic effects on female fertility parameters were detected in the 0.4 and 1.3 mg/kg group treated with indomethacin, but 8 of 10 rats in the 4 mg/kg group died or were sacrificed before completion of the dosing period. These results demonstrated that 2 weeks of indomethacin treatment is sufficient to detect unruptured follicles or luteinized cyst in the ovary. In addition, 4 weeks of dosing maybe required for induction of follicular cysts, although we could not clearly show that these histopathological changes would affect female fertility functions. These present studies suggest that a precise histopathological examination may be able to predict the effect of test articles on female reproductive functions. (+info)
Collaborative work on evaluation of ovarian toxicity. 13) Two- or four-week repeated dose studies and fertility study of PPAR alpha/gamma dual agonist in female rats.
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The main focus of this study was to determine the optimal dosing period in a repeated dose toxicity study based on toxic effects as assessed by ovarian morphological changes. To assess morphological and functional changes induced in the ovary by a peroxisome proliferator-activated receptor (PPAR) alpha/gamma dual agonist, the compound was administered to female rats at dose levels of 0, 4, 20, and 100 mg/kg/day in a repeated dose toxicity study for 2 or 4 weeks, and from 2 weeks prior to mating to Day 7 of pregnancy in a female fertility study. In the repeated dose toxicity study, an increase in atresia of large follicles, a decrease in corpora lutea, and an increase in stromal cells were observed in the treated groups. In addition, the granulosa cell exfoliations into antrum of large follicles and corpora lutea with retained oocyte are morphological characteristics induced by this compound, and they might be related with abnormal condition of ovulation. In the female fertility study, the pregnancy rate tended to decrease in the 100 mg/kg/day group. At necropsy, decreases in the number of corpora lutea, implantations and live embryos were noted in the 20 and 100 mg/kg/day group. No changes were observed in animals given 4 mg/kg/day. These findings indicated that histopathological changes in the ovary are important endpoints for evaluation of drugs inducing ovarian damage. In conclusion, a 2-week administration period is sufficient to detect ovarian toxicity of this test compound in the repeated dose toxicity study. (+info)
Collaborative work on evaluation of ovarian toxicity. 14) Two- or four-week repeated-dose studies and fertility study of atrazine in female rats.
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To investigate the optimal administration period for evaluating ovarian toxicity that reflects abnormal female fertility in the repeated dose toxicity study, atrazine, a potent herbicide with endocrine-disrupting activity, was administered to female Sprague-Dawley (Slc:SD) rats for two or four weeks at doses of 3, 30 or 300 mg/kg for the repeated dose toxicity study, and at doses of 3, 30 or 100 mg/kg for the female fertility study from two weeks before mating to Day 7 of gestation. In the two-week repeated dose toxicity study, prolongation of diestrus and histopathological findings such as loss of the currently formed corpora lutea, decrease in the numbers of previously formed corpora lutea, increase in large-sized atretic follicles, and swelling of the previously formed luteal cells were observed in the 300 mg/kg group, suggesting that atrazine had an anovulatory effect through suppression of the luteinizing hormone surge. In the female fertility study, copulation failure caused by prolongation of diestrus was observed in one animal in the 100 mg/kg group, which could be due to the anovulatory effect of atrazine. It is demonstrated that the effect of atrazine on female fertility can be assessed by detailed histopathological examination of ovaries in a two-week repeated dose toxicity study, provided the appropriate dose levels are selected. (+info)
Collaborative work on evaluation of ovarian toxicity. 15) Two- or four-week repeated-dose studies and fertility study of bromocriptine in female rats.
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The main focus of this study is to determine the optimal administration period concerning toxic effects on ovarian morphological changes in a repeated-dose toxicity study. To assess morphological and functional changes induced in the ovary by bromocriptine, the compound was administered to female rats at dose levels of 0, 0.08, 0.4 and 2 mg/kg for the 2- or 4-week repeated-dose toxicity study, and for the female fertility study from 2 weeks prior to mating to day 7 of gestation. In the 2-week repeated-dose toxicity study, increase of ovarian weights was observed at 2 mg/kg. In the 4-week repeated-dose toxicity study, ovarian weights were increased at 0.4 and 2 mg/kg. The number of corpora luteum was increased in the 0.4 and 2 mg/kg groups of the 2- and 4-week repeated-dose toxicity studies by histopathological examination of the ovaries. Bromocriptine did not affect estrous cyclicity in 2- and 4-week repeated dosing. In the female fertility study, although animals in any groups mated successfully, no females in 0.4 and 2 mg/kg groups were pregnant. There were no adverse effects on reproductive performance in the 0.08 mg/kg group. Based on these findings, the histopathological changes in the ovary are considered important parameters for evaluation of drugs including ovarian damage. We conclude that a 2-week administration period is sufficient to detect ovarian toxicity of bromocriptine in a repeated-dose toxicity study. (+info)
Collaborative work on evaluation of ovarian toxicity. 16) Effects of 2 or 4 weeks repeated dose studies and fertility study of Chlorpromazine hydrochloride in rats.
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In order to examine potential ovarian toxicity in 2 weeks or 4 weeks repeated-dose studies and a fertility study, chlorpromazine hydrochloride (CPZ) was administered orally to Crl:CD(SD) female rats at dosage levels of 0, 3, 10 and 30 mg/kg/day. In the repeated-dose studies, ovarian weights were decreased at > or = 10 mg/kg in the 4 weeks study and an increase in large atretic follicles was observed histopathologically at > or = 3 mg/kg and > or = 10 mg/kg in the 2 and 4 weeks studies, respectively. In addition, decreased uterine weights and/or atrophic findings in the uterus and vagina at 30 mg/kg and > or = 10 mg/kg, mucification in the vaginal epithelium and alveolar hyperplasia in the mammary gland at > or = 3 mg/kg and > or = 10 mg/kg were seen in the 2 and 4 weeks studies, respectively. Irregular estrous cycles were seen at > or = 3 mg/kg and > or = 10 mg/kg in the 2 and 4 weeks studies. The no-observed-adverse-effect level (NOAEL) for the 2 and 4 weeks studies was considered to be less than 3 mg/kg and 3 mg/kg, respectively. The fertility study with dosing from 2 weeks before mating to day 6 of gestation showed irregular estrous cycles at > or = 10 mg/kg and prolonged copulatory intervals and a reduced fertility index at 30 mg/kg; the NOAEL was therefore considered to be 3 mg/kg, which was higher than that in the 2 weeks study. These results showed that oral CPZ treatment induced ovarian toxicity with 2 weeks or longer treatment and changed the fertility parameters and was therefore concluded that a 2 weeks administration period is adequate to detect the ovarian toxicity of CPZ. (+info)