INDUCTION AND LOCALIZATION OF FAD-GLUCOSE DEHYDROGENASE (GLD) DURING ENCAPSULATION OF ABIOTIC IMPLANTS IN MANDUCA-SEXTA LARVAE

FAD-Glucose dehydrogenase (GLD) (EC 1.1.99.10) was assayed during the encapsulation response against abiotic implants (sterile latex) in fou rth instar Manduca sexta larvae. No GLD activity was detected in fresh hemolymph or hemocytes of control or sham-treated larvae. Two types o f responses occurred at 0.5 and 3h after implantation. In the majority of larvae, only the encapsulation had high levels of GLD specific act ivity. In the second response, low levels of GLD specific activity wer e detected in hemocytes and cell-free hemolymph but not in the encapsu lation. By 24h after implantation, GLD activity was detected in the en capsulation tissue of all larvae. Levels of GLD specific activity did not significantly differ over time (0.5-72 h) during encapsulation. Fr eezing cell-free hemolymph from control larvae activated otherwise ina ctive hemolymph stores of GLD. In vitro experiments and histochemical staining demonstrated that GLD activity was localized in granules of p lasmatocytes adhered to coverslips. Granules of both plasmatocytes and granulocytes contained GLD protein as detected by immunohistochemistr y. Based on previous characterization of GLD, we hypothesize that GLD participates in strengthening the encapsulation and in the killing rea ction, via reaction with quinones generated by phenoloxidase and subse quent production of free radicals.