Research on polychaete annelid osmoregulatory peptide(s) by immunocytochemical and physiological approaches. Computer reconstruction of the brain and evidence for a role of angiotensin-like molecules in Nereis (Hediste) diversicolor OF Müller.
Immunohistochemical and physiological studies were carried out on Nereis (Hediste) diversicolor OF Müller in order to obtain evidence concerning the neuroendocrine control of polychaete osmoregulation. The occurrence in this animal of peptides immunologically related to mammalian angiotensin II and I (AII and AI) and oxytocin (OT) was demonstrated in the brain and the ventral nerve cord (VNC) perikarya and nerve fibres as well as in a few peripheral structures (peripheral nerves, epithelial cells, nuchal organ, intestine and nephridia). The exact localization of immunoreactive cells was achieved by serial sections of brain and ventral nerve cord followed by a three-dimensional reconstruction of brain ganglionic nuclei using the CATIA ('Conception Assistée Tridimensionnelle Inter Active') Dassault system program. Injections of polyclonal antisera against AII or OT provoked a partial inhibition of the increase in body weight in Nereis exposed to hypo-osmotic medium. The effect of a-AII seemed more pronounced than that of a-OT. In a subsequent test, injections of synthetic AII and AII-amide (peptide recently isolated from an achaete (Salzet et al (1995) J Biol Chem 270, 1575-1582) enhanced the increase in body weight and, therefore, strengthened the hypothesis of the neuroendocrine control of Nereis osmoregulation. The antidiuretic effect of both synthetic peptides in this study was indicative of the exact role of Nereis endogenous molecule(s). AII was less potent than its amidated form. If AI-like can easily be struck off the list of putative endogenous osmoregulatory factors, the role of OT-like substance in Nereis osmoregulation, which is partially demonstrated in this study, needs to be clarified by further physiological experiments using injection of synthetic peptide(s) or endogenous substance(s). All these results are discussed and compared to those recently obtained in an achaete annelid (Salzet et al (1993) Brain Res 631, 247-255; Salzet et al (1993) Brain Res 601, 173-184; Salzet et al (1995) J Biol Chem 270, 1575-1582.
Fewou
J
J
Laboratoire de Phylogénie moléculaire des Annélides, Université des Sciences et Technologies de Lille, Villeneuve-d'Ascq, France.
Dhainaut-Courtois
N
N
D000809:Angiotensins / Q000378:metabolism*; D000818:Animals; D000845:Annelida / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D014882:Water-Electrolyte Balance
D000809:Angiotensins