RESUMEN
This study was undertaken to assess the effect of certain insecticides [viz.; avermectin, imidacloprid, methomyl, triazophos] and their binary combinations on the growth rate and weights of internal organs in albino rats, as well as to analyze the joint action of the tested mixtures against the rate of growth. The treatment with avermectin [at 1/10 LD[50]] caused weekly body weight gain in male and female rats very higher than those recorded for the control rats, while the treatment with imidacloprid [at 1/5 LD[50]] induced an opposite result. Also, most of the other tested treatments reduced the rate of growth. Relative to the body weights, a number of treatments [e.g. triazophos; avermectin + imidacloprid] were found to produce increases in the weights of heart, liver and spleen. Other treatments, such as methomyl [at 1/10 and 1/5 LD[50s]], caused obvious decreases in the relative weight of kidneys, testes, and ovaries, while the relative weight of lungs did not change significantly by the tested insecticides; either given singly or in paired combinations. The results of joint action analysis revealed that the most effective mixture inducing potentiation against the growth rate of male and female rats was entitled to the combination of avermectin + methomyl [Relative Interaction Index ; RII = 0.10 and 0.32 respectively]. Antagonistic effect was obtained with the mixture imidacloprid + triazophos against female rats [RII=1.15]