Hyperglycaemic factor from the corpora cardiaca of Manduca sexta (L.) (Lepidoptera: Sphingidae)

Abstract

It could be shown that in the corpora cardiaca of Manduca sexta there is a hyperglycaemic factor. The factor is found neither in the brain, nor the corpora allata, nor the ventral nerve cord. In this species, changes in phosphorylase activity were shown to be a much more sensitive assay for this factor than changes in fat body glycogen content or in haemolymph suger content. One-hundredth pair of corpora cardiaca per 1.3 ml of haemolymph proved enough to fully stimulate fat body glycogen phosphorylase. Phosphorylase was fully activated as early as about 3.5 min after the injection of the factor. The hyperglycaemic factor was shown to be most likely a heat-stable peptide which is digested by pepsin and chymotrypsin but not by trypsin. Glucagon activated phosphorylase, too, but only at 10 −5 M, which is extremely high compared to its action in vertebrates.