Localization and immunological characterization of insulin-like peptide(s)in the land snail Otala lactea (Mollusca : Pulmonata)

Insulin-like peptides were detected by means of immunological techniques in tissues of the land snail Otala lactea. Insulin-positive cells were detect ed in all the ganglia except the right parietal ganglion and visceral gangl ion. In the digestive tract, insulin-positive cells were found in the muscl e and connective tissue layer of the intestine. The amount of insulin-like peptide detected in acid-ethanol extract of brains and digestive tracts fro m active snails did not differ significantly from that in the corresponding tissues from estivating (dormant) ones. More insulin-like peptide was dete cted in hemolymph from active snails than in hemolymph from estivating ones . Brains from active snails released insulin-like peptide in vitro. Analysi s of the cerebral ganglia or digestive tract extracts by size-exclusion chr omatography and insulin RIA revealed more than one fraction with insulin im munoreactivity. Some of these fractions contained material with molecular m asses close to those of mammalian insulin or its subunits. Further analysis of the extracts by reverse-phase chromatography also revealed more than on e fraction with immunoreactivity. The immunoreactive material from the dige stive tract was found to be less hydrophobic than insulin. Western blot ana lysis of the cerebral ganglia extract revealed more than one band with insu lin immunoreactivity. Three of these bands had molecular masses very simila r to those of vertebrate insulin, its subunits, and its precursor.