ADIPOKINETIC HORMONE AND DEVELOPMENTAL-CHANGES OF THE RESPONSE OF FAT-BODY GLYCOGEN-PHOSPHORYLASE IN MANDUCA-SEXTA

The maximum percentage of active fat body glycogen phosphorylase which can be induced by the indigenous adipokinetic hormone (M-AKH) undergo es changes during the development of the tobacco hornworm, Manduca sex ta. In intact fifth-instar larvae and pharate pupae a maximum of 60-80 % can be achieved. Two picomoles of peptide were required in larvae we ighing 2-3 g, pharate pupae and pupae; 20 pmol in larger larvae (5.5-6 .5 g). In larvae 1 day before wandering (9-10 g), pupae and adults (bo th day 1 and day 2) 40% active phosphorylase was the maximum. Ligated abdomens from larvae weighing 9-10 g, however, showed a maximum phosph orylase activation of about 60%. The dilution of the injected peptide in different haemolymph volumes influences the results but cannot expl ain all the observed differences. Other parameters, e.g. presence of p eptidases in the haemolymph and on the surface of tissues bathed in ha emolymph or uptake of M-AKH into Malpighian tubules may undergo develo pmental changes which influence the residence time of the peptide in t he haemolymph.