The effect of acute manipulation of blood volume and osmolality on
plasma avt concentration in seawater flounder, platichthys
flesus.
Warne, J. M., R. J. Balment.
School of Biological Sciences, University of Manchester, Oxford
Road, Manchester M13 9PT, UK
APStracts 2:0155R, 1995.
Chronically cannulated seawater adapted flounder (Platichthys flesus)
were used unanesthetized and unrestrained in experimental series
which acutely manipulated blood volume and plasma osmolality to
determine their influence on plasma arginine vasotocin (AVT)
concentrations. Immunoreactive AVT was measured using a
radioimmunoassay validated for flounder and other teleosts. Following
haemorrhage induced hypovolaemia or hypervolaemia produced by saline
infusion no major changes in plasma AVT concentrations were detected.
Raising plasma osmolality by intraperitoneal injection of 1 M NaCl
compared with control 150 mM NaCl injected fish (329.4 +/- 3.4 vs
320.4 +/- 3.0 mOsm/kgH2O, p<0.05) produced an increase in plasma
AVT concentration (6.7 +/- 1.2 vs 4.2 +/- 0.2 fmol/ml, p<0.05).
In a separate study, plasma composition in a large number of
uncannulated seawater adapted flounder was determined. This
demonstrated a positive linear relationship between the natural
variation observed between fish in plasma AVT concentrations and
plasma osmolality and sodium and chloride concentrations. These data
indicate that AVT secretion in SW adapted flounder is closely related
and perhaps directly sensitive to changes in plasma tonicity.
Received 3 January 1995; accepted in final form 30 May 1995.
APS Manuscript Number R3-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.