Protein release from the larval fat body of the southwestern corn borer, Diatraea grandiosella: An in vitro study

The release of protein from the perivisceral fat body of non-diapausing, pre-diapausing and diapausing larvae of the southwestern corn borer, Diatraea grandiosella, was examined in vitro. Time course studies showed a selective release of proteins into macromolecule-free Grace's medium. The rate of release of individual proteins differed. The release of some proteins was partially inhibited by the incorporation of potassium cyanide (10^?2 M) and ouabain (5 × 10^?3 M) into the medium. During a 5 min incubation a single major high molecular weight protein fraction was released at a high rate from the fat body of both non-diapausing and diapausing larvae. A low molecular weight protein (the diapause-associated protein) was also released readily from the fat body of diapausing larvae. Although most proteins released from the fat body in vitro appeared to be present in the haemolymph in vivo, one notable exception was the absence of the diapause-associated protein from the haemolymph. The method holds promise for facilitating further studies of protein release from insect fat body.