title: Effects of dietary dieldrin on reproduction in the Swiss-Vancouver (SWV) mouse.
abstract: Reproduction was studied in SWV female mice that had raised one litter and then received either 0.2.5,5,10,15,20 or 25 parts/10(6) dietary dieldrin (n = 18 or 19 per group). Exposure began 4 weeks prior to the second mating and continued until day 28 postpartum (weaning). Fertile males were caged with the females during weeks 5-6 of exposure. Significantly mortality of the females occurred only at 20 and 25 parts/10(6) (89% and 56%, respectively) and all deaths occurred before parturition. Dieldrin did not affect behavioural oestrus. At 10 and 15 parts/10(6), 18% of the bred females did not become pregnant; all animals at lower doses and all survivors at higher doses were fertile. The gestation period was not affected. At 25 parts/10(6), the litter size was decreased by 17% over the control size (13.2 pups). The infertility and reduced fecundity resulted from a lesion(s) preceding implantation. Thus, in a separate experiment, 15 parts/10(6) increased the number of bred females that had no implantation sites 5 days post coitum while 25 parts/10(6) decreased the number of sites per pregnant female. As expected from the original dose-responses for infertility and decreased litter size, the converse effects did not occur. Pre-weaning mortality of all the pups occurred in 31%, 47%, 80% and 100% of the litters at 0,2.5,5, and larger than or equal to parts/10(6), respectively. Within the litters raised at 2.5 and 5 parts/10(6), the pup survival was not different from the controls (75%). Thus, in this strain, litter -oss is dieldrin's most important reproductive effect and it correlated with a dieldrin-induced maternal hepatomegaly. The birth weight of pups in litters that were lost was reduced by 3-13% and pre-death growth was reduced or absent. Pup-killing and pup-neglect were important proximate causes of mortality, but only at doses larger than or equal to 15 parts/10(6).
mesh_terms: D000818:Animals; D001724:Birth Weight / Q000187:drug effects; D004026:Dieldrin / Q000633:toxicity*; D010064:Embryo Implantation / Q000187:drug effects; D004971:Estrus / Q000187:drug effects; D005260:Female; D005298:Fertility / Q000187:drug effects; D005313:Fetal Death / Q000139:chemically induced; D008098:Litter Size / Q000187:drug effects; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D010060:Ovulation / Q000187:drug effects; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects; D012098:Reproduction / Q000187:drug effects*; D012737:Sex Factors
chemical_list: D004026:Dieldrin