Evidence for multiple forms of the prothoracicotropic hormone in Drosophila melanogaster and inciation of a new function

The prothoracicotropic hormone (PTTH) was extracted from brains of the fruit fly, Drosophila melanogaster , partially purified and characterized by chromatography and electrophoresis. In vitro bioassays of the fractions obtained from chromatography revealed the existence of at least two forms of PTTH, a large form (14-17 kDa: "big PTTH") and a small form (3-5 kDa: "small PTTH"). The neural extract was able to stimulate ring glands to secrete ecdysone in a dose-dependent manner in vitro. Moreover, when incubated with imaginal wing discs, the extract specifically simulated the synthesis of the heat-shock protein 83. This observation suggests that PTTH may have a hormonal role beyond its well-known function in the control of ecdysone secretion within the neuro-endocrine axis of brain and prothoracic glands.