Effect of ronnel after chronic feeding to dogs

Abstract

Ronnel, O,O-dimethyl- O-(2,4,5-trichlorophenyl) phosphorothioate, was subjected to a toxicity study lasting 2 yr in the dog. Throughout the period there were not any overt clinical signs that could be attributed to ronnel, and body weight did not appear to be affected even at the high level of intake of 10 mg/kg/day. There was no evidence of any effect of ronnel upon urinalysis, hematologic findings, blood biochemical findings (other than a depression of plasma cholinesterase), organ weights or the histologic appearance of the tissues. Ronnel was without adverse effect upon erythrodyte cholinesterase or brain cholinesterase. Depression of plasma cholinesterase was the only noteworthy effect observed in the study. Depression was significant at the 10 mg/kg/day dietary level ( P = 0.01), but was only slight at the intermediate 3 mg/kg/day level ( P < 0.05). Dogs in the intermediate group had plasma cholinesterase values which, overall, averaged 82% of pretreatment controls. Plasma cholinesterase values for the 1 mg/kg/day level were indistinguishable from those of controls. The unequivocal no-effect level of ronnel in dogs is concluded to be 1 mg/kg/day. However, considering that no other effects were observed in the study and that depression of plasma cholinesterase was generally within a 20% variation from pretreatment values, it is concluded that 3 mg ronnel/kg/day produced no significant toxicologic effect in dogs.