Farrukh HM, White M, Port JD, Handwerger D, Larrabee P, Klein J, Roden RA, Skerl L, Renlund DG, Feldman AM. Up-regulation of beta 2-adrenergic receptors in previously transplanted, denervated nonfailing human hearts.
J Am Coll Cardiol 1993;
22:1902-8. [PMID:
8245347 DOI:
10.1016/0735-1097(93)90777-x]
[Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
OBJECTIVES
The purpose of this study was to examine beta-adrenergic receptor signal transduction in denervated, previously transplanted human ventricular myocardium.
BACKGROUND
In model systems, surgical denervation typically results in both presynaptic and postsynaptic supersensitivity in beta-adrenergic receptor pathways and alteration in G protein-mediated signal transduction.
METHODS
We examined beta-adrenergic receptor signal transduction in the left and right ventricles removed from nine subjects with a previous transplant and surgical denervation 25 +/- 4 months after their first transplantation. Twenty-six hearts removed from organ donors served as control hearts.
RESULTS
Total beta-adrenergic receptor density and stimulation of muscle contraction in isolated right ventricular trabeculae by the nonselective agonist isoproterenol were similar in the transplant and donor groups. Beta 1-receptor density was not different in the left ventricles of the two groups but tended to be reduced (by 29%, p = 0.09) in transplant right ventricles. By contrast, beta 2-receptor density was higher in transplant left and right ventricles relative to the respective values in donor ventricles by 33% in left ventricles and 97% in right ventricles (both p < 0.05). Isoproterenol, which in particulate fractions of human heart stimulates adenylyl cyclase primarily via beta 2-receptors, produced a greater increase in cyclic adenosine monophosphate generation in membranes prepared from transplant left ventricles and right ventricles compared with donors. In contrast, guanosine 5'-[beta,gamma-imido]triphosphate, sodium fluoride and forskolin, which stimulate adenylyl cyclase through nonreceptor/G protein-sensitive mechanisms, yielded similar degrees of adenylyl cyclase stimulation in the two groups, and both pertussis toxin- and cholera toxin-catalyzed adenosine diphosphate ribosylation were not altered in transplanted left ventricles.
CONCLUSIONS
These data indicate that the transplanted human heart exhibits an up-regulation of functional beta 2-adrenergic receptors.
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