Impact of injecting hydrophilic silica beads on phenoloxidase activity in Helicoverpa armigera haemolymph

Insects use cellular and humoral immune systems to defend themselves from foreign bodies. We assayed the dynamics of plasma phenoloxidase (PO) activity in Helicoverpa armigera larvae after the injection of hydrophilic silica beads into the haemocoel, We also studied the effects of the activators trypsin and laminarin, and inhibitors p NPGB and PTU on PO activities in plasma after silica beads were injected. The results showed that PO activities increased markedly after the injection of silica beads. PO activities in plasma were increased by the presence of trypsin, but under similar conditions PO activities did not follow the same trend when activated by laminarin. There may be an accumulation of prophenoloxidases (proPO) after the intrusion of foreign objects causing proPO to be activated at the appropriate time. p NPGB and PTU can totally inhibit PO activities.