Adenylyl cyclase activity and glucose release from the liver of the
european eel, anguilla anguilla.
Fabbri, Elena, Laura Barbin, Antonio Capuzzo, and Carla Biondi.
Department of Biology, University of Ferrara, 44100 Ferrara,
Italy
APStracts 5:0271R, 1998.
The properties of adenylyl cyclase (ACase) in liver membranes of the
European eel (Anguilla anguilla) and the involvement of cAMP in
glucose release from isolated hepatocytes in response to
catecholamines were studied. Basal enzyme activity seemed essentially
unaffected by GTP, while a biphasic response to increasing nucleotide
concentrations was obtained in the presence of epinephrine. Eel liver
ACase was dose-dependently stimulated by GTP[gamma]S and inhibited by
GDP(S. ACase activity, intracellular cAMP levels and glucose release
from isolated hepatocytes were significantly enhanced by NaF,
forskolin, epinephrine and phenylephrine. The rise in cAMP production
stimulated by catecholamines was counteracted by propranolol, but not
by phentolamine. Catecholamine-induced glucose output was instead
partially antagonized by both phentolamine and propranolol. Complete
inhibition was obtained only by the simultaneous presence of the two
adrenergic antagonists. Glucose release from the cells was induced by
dibutyryl cAMP and by the calcium ionophore ionomycin. In summary,
these data provide the first characterization of eel liver ACase
system, and suggest a direct role for cAMP in the catecholamine
-dependent glucose output. Furthermore, the involvement of calcium
ions in this cellular response is hypothesized.
Received 2 February 1998; accepted in final form 10 July 1998.
APS Manuscript Number R45-8.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 30 July 1998