Effects of chlorpyriphos on the alpha-amylase activity in the in vivo and in vitro conditions: Case study: Sitophilus oryzea

Purpose: Insect-insecticide interaction, as a dynamic system, increases our knowledge to improve chemical application. Although modes of action in the most insecticides is obvious (direct action) but the other targets which may be affected after treatment are not determined (indirect action). In this study digestive enzymes were considered as potential targets for insecticides. Research method: Some of (three sample) adults that were exposed to the different insecticide concentrations were selected for in vivo analysis. In this part, internal organs (midgut) were homogenates and enzyme activity was determined. On the other hand, in the in vitro assays, nontoxic adults were selected and after dissection of the guts, incubated to the different insecticide manually. Fifty microliters enzyme solution with 450 μl toxic solutions incubated 30 min in the room temperature before enzyme assay. Findings: Twenty hours after exposure to the insecticides, gut of adults were dissected and used for in vivo experiment. Our data showed that there was a significant difference in the enzyme activity among different concentrations of chlorpyriphos. The highest and lowest level of enzyme inhibitory was occurred in the 2000 and 0 ppm (control). There was no significant difference between control (0 ppm) and 300 ppm.  Data in the in vitro experiment showed that enzyme activity was reduced in the toxic concentrations. Trend of enzyme inhibiting that occurred with chlorpyriphos was regular as the highest and lowest inhibiting were observed in the maximum (99.2 %) and minimum concentrations (7.4 %), respectively. Limitations: There is a problem in which how to correlate in vivo and in vitro results to practical toxicology. Originality/Value: Using of new insecticides with new and widespread mode of action can be recommended against postharvest pest in the practical entomology.