STRUCTURAL CHARACTERIZATION OF OSMOREGULATOR PEPTIDES FROM THE BRAIN OF THE LEECH THEROMYZON TESSULATUM - IPEPYVWD AND IPEPYVWD-AMIDE

Neurons immunoreactive to an antiserum (a-OT) directed specifically ag ainst the C-terminal part (prolyl-leucyl-glycinamide) of vertebrate ox ytocin (OT) were detected in the brain of the leech Theromyzon tessula tum. With high pressure gel permeation chromatography followed by reve rsed-phase HPLC on brain extracts, evidence was given of the presence of three peptides (P1, P2, P3) immunoreactive to a-OT. Results of inje ction experiments in T. tessulatum and of titrations of each peptide a t the different physiological stages of the animals which showed a pea k in peptide PI amount at stage 3B, indicated that P1 is the active OT -like peptide. Using three steps of reversed-phase HPLC, Edman degrada tion and electrospray mass spectrometry, two sequences for P1 (IPEPYVW D and IPEPYVWD-amide) were found. These peptides differ from peptides to the oxytocin/vasopressin family and are unique in the animal kingdo m. Confirmation of their action on the hydric balance and their distri bution in the CNS were presented.