UPTAKE, RETENTION, METABOLISM AND EXCRETION OF [22,23-H-3(2)]DIHYDROAZADIRACHTIN IN SCHISTOCERCA-GREGARIA

[22,23-H-3(2)]dihydroazadirachtin was used as a tracer of azadirachtin to follow the distribution and metabolism of the tertranortripenoid i n the locust Schistocerca gregaria. Injected tracer was rapidly remove d from the haemolymph into many of the locust tissues. This uptake was inhibited by a large excess of injected dihydroazadirachtin, suggesti ng that the uptake was by a specific mechanism. High concentrations of injected unlabelled derivatives of azadirachtin inhibited to differen t extents the clearance of the tracer from the haemolymph. The results suggest that azadirachtin and its derivatives have different affiniti es for the uptake mechanism. Radiolabelled dihydroazadirachtin applied topically was shown to penetrate the locust cuticle quite slowly. A l arge fraction of the tracer was present in the fat body as well as gut and nervous tissue. Binding was persistent and not easily displaced. There was no evidence that dihydroazadirachtin was secreted into the p rimary urine by an active pumping mechanism. Metabolism of the dihydro azadirachtin was largely restricted to fat body and crop.