To clarify the mechanism of sensitivity to an endotoxin lipopolysaccharide LPS0111:B4, which causes severe liver injury in a variety of animals, we have developed an in vitro assay to measure Kupffer cell-mediated cytotoxicity in the human liver cell line, WRL68. This assay could detect the decrease in Kupffer cell activity induced by gadolinium chloride (GdCl₃), which is an inhibitor in Kupffer cells. Among Kupffer cells derived from dogs, rats, and monkeys, LPS-activated canine Kupffer cells exhibited remarkably high cytotoxicity against WRL68 cells. This species difference is correlated with a species difference in the lethality of LPS0111:B4. Additionally, the conditioned medium of LPS-activated canine Kupffer cells was also cytotoxic to WRL68 cells. To identify the mediators of this cytotoxicity, we measured the accelerated release of interleukin-1β, and interleukin-6 from Kupffer cells on stimulation with LPS0111:B4. From the correlation of the response to LPS0111:B4, interleukin-1β and interleukin-6 are considered to be responsible for the canine Kupffer cell-mediated cytotoxicity of LPS0111:B4.

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Dual fluorescent staining (DFS) with calcein acetoxy methyl ester (CAM), which labels the cellular esterase activity that is a major component of energy metabolism in cellular mitochondria, and with ethidium homodimer-1 (EthD-1) was used to evaluate mitochondrial function and membrane integrity in rat spermatozoa. The spermatozoa stained by DFS could be classified into three different populations microscopically when excited at 490 nm after 60 min incubation. 1) Spermatozoa, which were stained with CAM alone and had maintained either mitochondrial function or membrane integrity, were identified as live during incubation. 2) Spermatozoa, which were stained with EthD-1 alone and had lost either mitochondrial function or membrane integrity, were identified as already dead at the beginning of incubation. 3) Spermatozoa, which were stained with both CAM and EthD-1 and had maintained mitochondrial function with membrane breached, were identified as having died during incubation. Two toxicological tests, an in vitro triton X-100 experiment and an in vivo nitrobenzene experiment, were done. All spermatozoa were immobilized and lost either mitochondrial function or membrane integrity by 1.0% triton X-100 treatment. Almost no motile sperm were found at 0.1% in the triton X-100 group and in the groups treated with 60 and 40 mg/kg/day of nitrobenzene, and these spermatozoa maintained their mitochondrial function but had their membrane breached. In conclusion, the DFS procedure, which uses CAM and EthD-1, can clearly and visually identify the population of viable and dead spermatozoa simultaneously by fluorescence microscopy in rats. This is a useful technique to characterize sperm status, which is determined by the mitochondrial function assessed by CAM and membrane integrity evaluated by EthD-1.

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Flutamide, which has antiandrogenic properties, was administered to pregnant rats, and effects on male offspring were examined. Crj : CD (SD) IGS (SPF) females were administered flutamide (0.15, 0.6, 2.5, 10.0, 100 mg/kg, P.O.) from gestation Day 14 to post parturition Day 3. The number of pups, body weights, clinical features, anogenital distance (AGD), nipple retention, testicular descent, and urogenital malformation in F1 males were examined. Hormone measurement, necropsy and histopathological examination were carried out at post-neonatal Day 4 (PND 4) and PND 60. Sperm analysis was also carried out at PND 60. Decrease in body weight was seen in the 100 mg/kg group and the AGD was decreased at 2.5 mg/kg and above. Retention of nipples, hypospadia, vaginal pouches, penis malformation, unilateral ectopic testis, and decrease of organ weights (prostate, seminal vesicles, levator ani muscle plus bulbocavernosus muscle, testis) were observed at 10 mg/kg and above. Testicular testosterone (T) was increased significantly with 100 mg/kg at PND 4 and tendencies for increase were observed in serum T, LH and FSH at 10 mg/kg and more at the same time point. In contrast, elevated levels of LH and FSH were seen with 100 mg/kg at PND 60. Histopathological examination revealed defects or hypoplastic changes of genital organs (≥10 mg/kg), squamous metaplasia (10 mg/kg) or mucification (100 mg/kg) of the urethral diverticulum epithelium and inflammation of genital organs (100 mg/kg). Though only undescended testes lacked spermatogenesis at 10 mg/kg, atrophic change of seminiferous tubules and azoospermia were observed in the 100 mg/kg group, despite testicular descent. Perinatal administration of flutamide affected F1 male rats at 2.5 mg/kg and above. In addition to urogenital malformation, 100 mg/kg flutamide caused high LH and FSH levels at PND 60. This study indicates that the most sensitive parameter is AGD, whereby reduction was observed at 2.5 mg/kg. A clear no-effect level (NOEL: 0.6 mg/kg) was obtained in this perinatal study of an antiandrogenic chemical.

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The antidiabetic agent troglitazone was given to groups of 4 cynomolgus monkeys per sex at 300, 600, or 1200 mg/kg daily by gavage for 52 weeks. A group of 4 monkeys per sex received vehicle alone and served as controls. Emesis and soft stool or diarrhea occurred sporadically in all troglitazone-treated groups, but did not compromise animal health. There were no effects on body weight or food consumption, or ophthalmologic, electrocardiographic, or echocardiographic parameters. Erythrocyte count, hemoglobin, and hematocrit decreased 8% to 16% in males at all doses and serum cholesterol decreased 30% to 46% in both sexes at all doses. Urinary ketones were increased in several animals at 600 and 1200 mg/kg. Absolute and relative liver weights increased at all doses in both sexes by 40% to 71%. The only microscopic change attributable to troglitazone treatment was minimal to mild bile duct hyperplasia in males at all doses and in females at 600 and 1200 mg/kg. No differences in systemic exposure were apparent between sexes. Over the dose range tested, AUC_(0-24) values were 27 to 102 μg·hr/ml of troglitazone, 401 to 2060 μg·hr/ml of its sulfate conjugate, and 34 to 312 μg·hr/ml of its quinone metabolite. Therefore, oral administration of troglitazone to monkeys at 300, 600, and 1200 mg/kg for 52 weeks resulted in significant systemic exposure, with only minimal gastrointestinal, hematologic, and hepatic effects.

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Endocrinological assessment of male reproductive toxicity was carried out in SD-Slc male rats treated with 5-FU (0, 20, 30 mg/kg/day) orally for 2-week or 4-week term. Serum hormone levels including GnRH, FSH, LH, prolactin, total and free testosterone, inhibin B, pro-alpha C, and activin A were determined as well as histopathological examination of the reproductive organs. The 5-FU treated groups showed histopathological changes in the testis such as degeneration of seminiferous epithelium. An obvious decrease in serum testosterone level was observed with a reduced organ weight of the seminal vesicle and prostate. However, no significant changes were noted in serum LH or FSH levels, nor in the morphological examination of the Leydig cells. Decreased serum levels were noted in activin A and prolactin. An increased serum level was noted in GnRH and pro-alpha C whose synthesis is regulated by FSH. Serum inhibin B levels showed a tendency toward decreasing with morphological change (vacuolation) in Sertoli cells. These results indicated that male reproductive toxicity induced by 5-FU would be augmented by decreased serum prolactin and testosterone levels as well as a decreased function of Sertoli cell, in addition to the direct cytotoxic effects on germ cells. It is suggested that these endocrinological changes related to male reproductive toxicities can be detected even in the 2-week-treated study.

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The potential of purple sweet potato color (PSPC) and red cabbage color (RCC), natural anthocyanin food colors, to modify colorectal carcinogenesis was investigated in male F344/DuCrj rats, initially treated with 1,2-dimethylhydrazine (DMH) and receiving 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in the diet. After DMH initiation, PSPC and RCC were given at a dietary level of 5.0% in combination with 0.02% PhIP until week 36. No PSPC or RCC-treatment-related changes in clinical signs and body weight were found. Incidences and multiplicities of colorectal adenomas and carcinomas in rats initiated with DMH were clearly increased by PhIP. In contrast, lesion development was suppressed by RCC, or tended to be inhibited by PSPC administration. Furthermore, in the non-DMH initiation groups, induction of aberrant crypt foci (ACF) by PhIP was significantly decreased by RCC supplementation. The results thus demonstrate that while PhIP clearly exerts promoting effects on DMH-induced colorectal carcinogenesis, these can be reduced by 5.0% PSPC or 5.0% RCC in a diet under the present experimental conditions.

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