The purpose of this study was to assess the effects of Guthion, a pesticide with anticholinesterase activity, on development in rats and mice. A preliminary toxicity study with Guthion indicated that a 35 LD50 dose for virgin rats and a 10 day LD50 dose for virgin mice was between 4 and 8 mg/kg/day for both species. On the basis of this data, doses of 0, 1.25, 2.5, and 5.0 mg/kg/day were selected for the developmental study, which consisted of two phases. During the first phase, pregnant rats and mice were treated for 10 days starting on gestational day 6. The high dose affected maternal welfare only in rats. Guthion did not significantly increase in a dose-related manner any of the specific anomalies observed in either rats or mice. During the second phase, pregnant rats were treated from gestational day 6 to post-partum day 21. Dams in the high dose group were more sensitive to Guthion later in gestation with the result that deaths and signs of anticholinesterase toxicity increased during this time. Guthion also adversely affected maternal welfare in this group. As a result of Guthion toxicity, only one litter survived until weaning. The inability to dissociate toxicity in adult and developing animals suggests that Guthion has little primary effect on the development of rats or mice.

Project Officer: Ronald L. Baron. Midwest Research Institute "August 1978." "EPA-600/1-78-056."