In addition to the five 70-kDa heat shock proteins (HSP70) (13) and an additional thymidine kinase (TK) gene (see Fig. 1 A-C

The alkylphenol breakdown products of alkylphenol ethoxylates have been shown in in vitro studies to be weakly estrogenic, but few in vivo data address this issue in mammals. Because estrogens have been found to be most potent during developmental/perinatal exposures, this study maximized developmental exposure to nonylphenol (NP) by treating 3.5 generations of Sprague-Dawley rats to NP in diet at 200, 650, and 2000 ppm to determine the range and severity of any toxicity. Dose rate was higher for younger rats; calculated dose ranges were 9-35, 30-100, and 100-350 mg/kg/d for the low (200NP), middle (650NP), and high (2000NP) dose groups, respectively. There were adult (F0, F1, F2) and postnatal day (pnd) 21 (F1, F2, F3) necropsies; the oldest F3 rats were killed on pnd 55-58. Body weight gain was reduced by 8-10% in the 650NP and 2000NP groups. Vaginal opening was accelerated by approximately 2 days (650NP) and approximately 6 days (2000NP) in F1, F2, and F3 generations. Uterine weights at pnd 21 were increased in 650NP (14%) and 2000NP (50%) F1 females, but not in other generations. Testis descent, anogenital distance, and preputial separation were not consistently changed. No consistent changes were seen in pup number, weight or viability, litter indices, or other functional reproductive measures. Relative ovary weight in F2 adults was decreased at 650NP and 2000NP by 12%; relative ovary was unchanged in other generations. Follicle counts were unchanged in F2 adults. Sperm indices, including CASA measures, were unchanged in F0 and F1 males. In F2 rats, epididymal sperm density was reduced by 8% and 13% at 650NP and 2000NP, respectively. Testicular spermatid count was reduced by 13% in 2000NP F2 males; testis and epididymis weights were unchanged. Erosion of gastric and duodenal mucosa was monitored grossly and microscopically, and never found. Kidney weights were increased in 650NP and 2000NP males, and renal medullary tubular dilatation and cyst formation were noted in all generations of males, and often at the lowest dose tested. These data show that NP had limited effects on the reproductive system in the presence of measurable nephrotoxicity. The F2 sperm effects are either statistical/biological "noise," or imply heretofore unknown pharmacokinetics or toxicodynamics. These sperm data should be interpreted cautiously until the findings are repeated.

was published in 1993 (NAS, 1993). Among the recommenand evaluated for changes to the immune system and for reproducdations were changes in the risk assessment process, changes tive toxicity. Dose-dependent amounts of MXC and metabolites were present in milk and plasma of dams and pups. The high dose in surveillance of the food supply, and a call for better inforof MXC reduced litter size by É17%. Ano-genital distance was mation on the effects of pesticides on the developing aniunchanged, although vaginal opening was accelerated in all mals' reproductive, immune, and central nervous systems. treated groups, and male prepuce separation was delayed at the The National Toxicology Program, in conjunction with middle and high doses by 8 and 34 days, respectively. In the collaborators at EPA's National Health and Environmental neurobehavioral evaluation, high-dose males were more excitable, Effects Research Laboratory, developed a design that would but other changes were inconsistent and insubstantial. A decrease address some of the data needs identified in the NAS report. in the antibody plaque-forming cell response was seen in malesThe NAS report identified the exposure period of concern only. Adult estrous cyclicity was disrupted at 50 and 150MXC, for humans as being from the last trimester of pregnancy to doses which also showed reduced rates of pregnancy and delivery. years of age, a range that is approximated in the rodentUterine weights (corrected for pregnancy) were reduced in all study used here. Because the concern was on direct contreated pregnant females. High-dose males impregnated fewer untreated females; epididymal sperm count and testis weight were sumption of pesticide residues, we dosed dams for the week before and the week after birth, and then direct-dosed the pups from postnatal day (pnd)7 to pnd42, the approximate This article has been reviewed by the National Health and Environmental age of puberty in these rats. Animals are taken at various Effects Laboratory, U.S. Environmental Protection Agency, and approved points in the dosing period to ascertain effects: compound for publication. Approval does not signify that the contents necessarily in milk is determined at pnd7, the last day of dosing for the reflect the views of the Agency nor does mention of trade names or commercial products constitute endorsement or recommendation for use.dam, and the time during her dosing when she is likely to 138