RESUMEN
Since pesticides have been shown to interact with P-glycoprotein (P-gp), the purpose of this study was to examine the possible role of P-gp in pesticide resistance in the tobacco budworm (Heliothis virescens). Using three P-gp antibodies, P-gp expression in various resistant populations of tobacco budworms was found to be 2-6-times that of the susceptible larvae. Tobacco budworm P-gp was glycosylated and localized primarily in the cuticle and fat body with little expression in the mid gut. To determine the role of P-gp in pesticide resistance, resistant tobacco budworm larvae were treated with a P-gp inhibitor, quinidine, and challenged with various doses of thiodicarb. Inhibition of P-gp decreased the LD50 for thiodicarb by a factor of 12.5. Quinidine treatment did not result in a significant inhibition of the P-450 system nor did it alter the feeding of the larvae, suggesting the potential involvement of P-gp in pesticide resistance. An age-dependent increase in P-gp expression was detected in resistant larvae as compared to control, susceptible larvae. This correlates with the reported age-dependent increase in resistance and is further evidence supporting the role of P-gp in the development of pesticide resistance.
Asunto(s)
Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/fisiología , Resistencia a Múltiples Medicamentos/fisiología , Insecticidas/toxicidad , Lepidópteros/efectos de los fármacos , Tiocarbamatos/toxicidad , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/análisis , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/antagonistas & inhibidores , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/química , Animales , Anisoles/metabolismo , Inhibidores Enzimáticos del Citocromo P-450 , Sistema Enzimático del Citocromo P-450/metabolismo , Inhibidores Enzimáticos/farmacología , Glicosilación , Larva/química , Larva/efectos de los fármacos , Lepidópteros/química , Lepidópteros/crecimiento & desarrollo , Dosificación Letal Mediana , Peso Molecular , Butóxido de Piperonilo/farmacología , Quinidina/farmacología , Quinina/farmacología , Vinblastina/farmacologíaRESUMEN
Pesticides have been shown to interact with the multidrug resistance protein associated with cancer chemotherapy, P-glycoprotein (P-gp). P-gp, therefore, has also been implicated in the development of pesticide resistance. The purpose of this study was to characterize the effect P-gp has on the accumulation of the carbamate pesticide, thiodicarb. For these studies, resistant tobacco budworm larvae, expressing four times the P-gp as susceptible larvae, were pretreated with the P-gp inhibitor, quinidine, and challenged topically with thiodicarb. Quinidine enhanced thiodicarb toxicity in a dose-dependent manner, with mortality in the presence of P-gp inhibition increased up to 33%. Quinidine treatment increased [14C]thiodicarb accumulation 2- to 3-fold as compared to thiodicarb treatment alone. This study suggests that P-gp contributes to quinidine synergism of thiodicarb toxicity and suggests that P-gp may be involved in cuticular resistance to pesticides.
