Stimulation and inhibition of cAMP accumulation by glucagon in canine hepatocytes.

T. Grady, M. Fickova, H. S. Tager, D. Trivedi, V. J. Hruby

Research output: Contribution to journalArticle

Abstract

We have examined, by use of isolated canine hepatocytes and selected hormone analogs, the mechanisms by which glucagon modifies the accumulation of cellular cAMP. Low concentrations of glucagon (less than or equal to 3 nM) enhanced the accumulation of hepatocyte cAMP, whereas higher concentrations of the hormone diminished the effectiveness of lower ones. This biphasic concentration dependence was observed as well for some glucagon analogs, but not for others, and was apparent for cells incubated in the presence or absence of theophylline. Glucagon at high concentrations (greater than or equal to 10 nM) also inhibited the accumulation of cAMP induced by isoproterenol. The inhibitory effect of glucagon in both of these systems was reversed or attenuated by cell incubations involving the use of pertussis toxin (islet-activating protein) or a peptide antagonist of the glucagon-adenylyl cyclase system. We conclude that (a) glucagon, through its interaction with high and low affinity binding sites, can either stimulate or inhibit the production of hepatocyte cAMP; (b) the inhibitory action of the hormone appears to arise from interactions of ligand with a subset of these binding sites and to require structural characteristics in addition to those that determine receptor binding affinity per se; and (c) the glucagon and adrenergic systems involved in stimulating cAMP accumulation are linked, at least with regard to the negative effect induced by high concentrations of glucagon.

Original languageEnglish (US)
Pages (from-to)15514-15520
Number of pages7
JournalJournal of Biological Chemistry
Volume262
Issue number32
StatePublished - Nov 15 1987
Externally publishedYes

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Glucagon
Canidae
Hepatocytes
Pertussis Toxin
Hormones
Binding Sites
Theophylline
Isoproterenol
Adenylyl Cyclases
Adrenergic Agents
Ligands
Peptides

ASJC Scopus subject areas

  • Biochemistry

Cite this

Stimulation and inhibition of cAMP accumulation by glucagon in canine hepatocytes. / Grady, T.; Fickova, M.; Tager, H. S.; Trivedi, D.; Hruby, V. J.

In: Journal of Biological Chemistry, Vol. 262, No. 32, 15.11.1987, p. 15514-15520.

Research output: Contribution to journalArticle

Grady, T, Fickova, M, Tager, HS, Trivedi, D & Hruby, VJ 1987, 'Stimulation and inhibition of cAMP accumulation by glucagon in canine hepatocytes.', Journal of Biological Chemistry, vol. 262, no. 32, pp. 15514-15520.
Grady, T. ; Fickova, M. ; Tager, H. S. ; Trivedi, D. ; Hruby, V. J. / Stimulation and inhibition of cAMP accumulation by glucagon in canine hepatocytes. In: Journal of Biological Chemistry. 1987 ; Vol. 262, No. 32. pp. 15514-15520.
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