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 MULLER
J. Fewou et N. Dhainautcourtois, 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 MULLER, Biology of the cell, 85(1), 1995, pp. 21-33
Immunohistochemical and physiological studies were carried out on Nere
is (Hediste) diversicolor OF Muller in order to obtain evidence concer
ning the neuroendocrine control of polychaete osmoregulation. The occu
rrence 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 fibr
es as well as in a few peripheral structures (peripheral nerves, epith
elial cells, nuchal organ, intestine and nephridia). The exact localiz
ation 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 Assistee Trid
imensionnelle Inter Active') Dassault system program. Injections of po
lyclonal antisera against AII or OT provoked a partial inhibition of t
he increase in body weight in Nereis exposed to hypo-osmotic medium. T
he effect of a-All seemed more pronounced than that of a-OT. In a subs
equent test, injections of synthetic AII and AII-amide (peptide recent
ly isolated from an achaete (Salzet et al (1995) J Biol Chem 270, 1575
-1582) enhanced the increase in body weight and, therefore, strenghthe
ned the hypothesis of the neuroendocrine control of Nereis osmoregulat
ion. 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 Al-like can easily be stru
ck off the list of putative endogenous osmoregulaory factors, the role
of OT-like substance in Nereis osmoregulation, which is partially dem
onstrated in this study, needs to be clarified by further physiologica
l experiments using injection of synthetic peptide(s) or endogenous su
bstance(s). All these results are discussed and compared to those rece
ntly obtained in an achaete annelid (Salzet er al (1993) Brain Res 631
, 247-255; Salzet et al (1993) Brain Res 601, 173-184; Salzet et al (1
995) J Biol Chem 270, 1575-1582.