Evaluation of chronic exposure of the male rat reproductive system to the insecticide methomyl.

Carbamate insecticides are widely used in industry, agriculture and for public health purposes. Numerous incidents of acute carbamate poisoning have resulted from inhalation of sprays or contamination of crops or food. This work was conducted to study the effect of chronic exposure to methomyl on hormonal, histopathological and histochemical changes in rat testes. The treated group received methomyl orally (17 mg kg(-1)in saline) daily for 2 months, while the control group received saline. A significant decrease in the level of testosterone was observed in the intoxicated animals, while the levels of FSH, LH and prolactin were significantly increased. Histopathological studies of the intoxicated rat testes revealed variable degrees of degenerative changes in the seminiferous tubules up to total cellular destruction. As regards the histochemical results, it was found that both acid phosphatase and alpha esterase enzyme activity was significantly increased compared to the control group. On the other hand succinic dehydrogenase enzyme activity was significantly reduced. No significant change was observed in alkaline phosphatase enzyme activity. The hormonal changes and testicular damage continued for 30 days after withdrawal of the insecticide indicating a persistent effect. From the above-mentioned findings, it has been concluded that chronic exposure to methomyl insecticide has deleterious effects on rat testes. Therefore application of such insecticide should be limited to a designed program with special care in handling to limit or minimize its hazards. Copyright 2001 Academic Press.