Thesis (M.Sc. in Pharm.)--Chulalongkorn University, 1997

Studies on the effects of methomyl, a highly toxic carbamate insecticide, in rats receiving a single dose and repeated doses orally were carried out. The rats treated with single doses of 3-7 mg/kg of methomyl showed significant increase in total lactate dehydrogenase (LDH) activity on day 1. The highest total LDH enzyme activity occurred in the rats receiving 7 mg/kg of methomyl on day 3 after dosing. Subsequently, the level of LDH activity declined to normal level on days 5 and 7 after dosing. These high LDH activities were concurrent with significantly increased LDH-3 and LDH-4 level. Both spleen weight and splenocyte viability were significantly reduced in rats treated with an acute dose of 6 and 8 mg/kg of methomyl on days 1 and 3. Splenotoxicity effect seen was protected by pretreatment with N-acetylcysteine (NAC). These results are discussed in terms of various mechanisms which might be involved. The author suggests that mechanisms how NAC which acts as a scavenger of the free radical generated by injured cells protect against methomyl toxicity should be further investigated.