Hormonal regulation of carbohydrate metabolism in the blowfly Phormia terraenovae

Abstract

The corpus cardiacum-corpus allatum complex of the blowfly, Phormia terraenovae, contains a factor causing activation of glycogen phosphorylase and an increase of the total carbohydrate concentration in the haemolymph. Trehalose which contributes about 90% of the blowfly's normal blood sugar is preferentially elevated upon gland injection. Hypertrehalosaemia is also induced when blowfly gland extract is injected into the American cockroach, Periplaneta americana, as a test insect. Separation of a methanolic corpus cardiacum extract from blowflies on reversed-phase high-performance liquid chromatography results in only one distinct absorbance peak having a fair hypertrehalosaemic activity in cockroaches and activating blowfly abdominal glycogen phosphorylase. The material elutes slightly later than the hypertrehalosaemic hormone II (Pea-CAH-II) of P. americana. There is no evidence for a second hypertrehalosaemic factor or for antagonistically acting molecules. Stress induced by shaking blowflies at various frequencies results in an activation of glycogen phosphorylase and blood carbohydrate elevation; both actions are unaffected by the age of the experimental insects (tested up to 7 days after imaginal ecdysis). Flight (1 h) causes a 50% decrease in the glycogen content of the blowfly and a 2-fold increase in haemolymph carbohydrate levels. Release of the hypertrehalosaemic material of P. terraenovae is also shown by collecting and purifying blood from stressed blowflies, and injecting the peptide fraction into test cockroaches, which then unequivocally show a hypertrehalosaemic response.