Detection of [22,23- 3H 2] dihydroazadirachtin binding sites on Schistocerca gregaria (Forskål) testes membranes

Specific binding of [22,23- 3H 2]dihydroazadirachtin in vitro was established using testes membranes from adult male Schistocerca gregaria. This specific binding was time dependent and saturable. Analysis of the saturation characteristics indicated one population of binding sites ( K d 8.7 nM, B max 0.3 pmol/mg protein). Once at a maximum level of binding, dissociation of the radioligand:membrane complex in the presence of unlabelled parent compound was incomplete. Azadirachtin and dihydroazadirachtin were almost equally potent inhibitors of binding of the radioligand when added in excess in competition studies whereas 3-tigloylazadirachtol was less potent and 22-α-bromo-22,23-dihydro-23-α,β-ethoxyazadirachtin was least effective at the concentrations tested. Other tissues tested (Malpighian tubules, fat body, accessory glands, ovaries, skeletal muscle and midgut) showed less specific binding under the conditions used.