Characterization of pregnancy outcome following thiram-induced ovulatory delay in the female rat.
A single injection of the dithiocarbamate fungicide, thiram, suppresses the proestrous surge of LH and delays ovulation for 24 h. In this study, we examined fertility after a thiram-induced delayed ovulation. Females were injected with thiram (50 mg/kg, IP) on proestrus (1300 h) and mated on the following evening. Control and thiram-treated, but nondelayed, females were injected and mated on the same day. The number of females in the thiram-delayed group that became pregnant was reduced and litter size on GD 20 was reduced: however, no obvious morphological anomalies were seen. The number of pregnant females and litter size was not altered in the thiram-nondelayed rats, indicating that it is the thiram-induced delay in ovulation and not the exposure to thiram per se that was responsible for altered pregnancy outcome. On GD 7 and 11, the number of live fetuses per litter was reduced in the delayed females, but the number of implantation sites was not different from controls. On GD 11 the mean developmental score, head length, crown-rump length, and somite number in the delayed group were also reduced, indicating retarded development of live embryos. These results demonstrate that delayed ovulation induced by a single thiram exposure does not alter the number of oocytes released or the number that implant. However, the concept from these females are compromised during midgestation.
Stoker
T E
TE
Endocrinology Branch, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
Cooper
R L
RL
Goldman
J M
JM
Andrews
J E
JE
D000818:Animals; D000935:Antifungal Agents / Q000633:toxicity*; D004971:Estrus / Q000187:drug effects*; D005260:Female; D005298:Fertility / Q000187:drug effects*; D005327:Fetal Resorption / Q000139:chemically induced*; D011247:Pregnancy; D051381:Rats; D013893:Thiram / Q000633:toxicity*
D000935:Antifungal Agents; D013893:Thiram