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Increase in functional activity rather than in amount of Gi-alpha in failing human heart with dilated cardiomyopathy.

Journal article
Authors Michael Fu
Qi-Ming Liang
Finn Waagstein
Johan Hoebeke
C Sylvén
E Jansson
P Sotonyi
Åke Hjalmarson
Published in Cardiovascular research
Volume 26
Issue 10
Pages 950-5
ISSN 0008-6363
Publication year 1992
Published at Wallenberg Laboratory
Pages 950-5
Language en
Keywords Adenylate Cyclase, metabolism, Cardiomyopathy, Dilated, metabolism, physiopathology, Enzyme-Linked Immunosorbent Assay, GTP-Binding Proteins, metabolism, Heart, physiopathology, Humans, Immunoblotting, Receptors, Adrenergic, beta, metabolism, Receptors, Muscarinic, metabolism
Subject categories Physiology, Cell and Molecular Biology


OBJECTIVE: The aim was to investigate whether or not increased pertussis toxin catalysed ADP ribosylation correlates with increased amount of Gi-alpha in failing human heart. DESIGN: Antisera raised against unique synthetic peptides corresponding to alpha subunits of Gs and Gi 1-3 were used in immunoblotting and ELISA to determine amounts of various G proteins. Adenylyl cyclase activity, beta adrenoceptors, and muscarinic receptors were then measured in cardiomyopathic hearts (n = 6) obtained at transplant in order to study whether or not an altered expression of G proteins has relevance to the integrity and function of the receptor--adenylyl cyclase system. Six non-failing control hearts were also studied. RESULTS: No significant differences in the peptide equivalent amounts of either Gs or Gi were found in the failing human heart as compared to the non-failing heart. However, functional activity of Gi was shown to increase significantly since there was a decrease in basal (57%), isoprenaline stimulated (60%), and guanyliminodiphosphate stimulated (52%) adenylyl cyclase activity. In contrast the density of beta adrenoceptors was markedly decreased (51%) in failing human heart in comparison to non-failing hearts. Neither the density nor the affinity of muscarinic receptors changed in the failing human heart. CONCLUSION: These results suggest that in the failing human heart, there is an increase in functional activity rather than in amount of Gi, and an important part of functional expression of Gi-alpha may be regulated at the post-translational level.

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