Locust ion transport peptide (ITP): A putative hormone controlling water and ionic balance in terrestrial insects

Abstract

SYNOPSIS. The anterior (ileum) and posterior (rectum) segments of the locust hindgut constitute the reabsorptive regions of the excretory system, which conserves or eliminates body water and solutes as required for osmotic homeostasis. Hindgut transport mechanisms in the desert locust have previously been well described but the neuropeptide hormones that may naturally control these processes are only now being identified. Ion Transport Peptide (ITP) has been isolated from locust corpus cardiacum (CC) and its full sequence of 72 amino acids deduced from its cDNA. Native ITP has the same actions as crude CC extracts in stimulating Cl~, Na+, K+, and fluid absorption and inhibiting H secretion (i.e., influencing pH regulation). The deduced amino acid sequence of ITP was confirmed by showing biological activity of expressed and synthetic forms of this peptide. ITP ' has high sequence homology with a large family of crustacean hormones that include hyperglycaemic (CHH) and moult-inhibiting hormones (MIH) and is the first member reported outside crustaceans.