The effects of endogenous phospholipase A2 activation on beta adrenoceptor function in cardiac cells

Bobik, A, Campbell, J, Snow, P and Little, PJ (1983) The effects of endogenous phospholipase A2 activation on beta adrenoceptor function in cardiac cells. Journal of Molecular and Cellular Cardiology, 15 11: 759-767. doi:10.1016/0022-2828(83)90335-8


Author Bobik, A
Campbell, J
Snow, P
Little, PJ
Title The effects of endogenous phospholipase A2 activation on beta adrenoceptor function in cardiac cells
Journal name Journal of Molecular and Cellular Cardiology   Check publisher's open access policy
ISSN 0022-2828
Publication date 1983-01-01
Year available 1983
Sub-type Article (original research)
DOI 10.1016/0022-2828(83)90335-8
Volume 15
Issue 11
Start page 759
End page 767
Total pages 9
Publisher ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
Language eng
Subject 1312 Molecular Biology
2705 Cardiology and Cardiovascular Medicine
Abstract The effects of endogenous phospholipase A2 activation by melittin on components of the beta adrenoceptor linked adenylate cyclase system were examined in cultured cardiac cells. Exposure of cardiac cells for one hour to melittin concentrations ranging from 0.125 μg/ml to 5.0 μg/ml induced a concentration dependent hydrolysis of radioactively labelled phospholipids and loss of lysophospholipids from the cell membrane. Melittin concentrations of 2.5 μg/ml or greater markedly attenuated the isoprenaline induced rise in cyclic AMP. In vitro studies using cell homogenates suggest that phospholipase A2 activation by the higher concentration of melittin (5 μg/ml) partially uncoupled the beta adrenoceptor from adenylate cyclase. Beta adrenoceptor number estimated by 125I-iodohydroxybenzylpindolol specific binding as well as the affinity of isoprenaline for these binding sites were unaffected by melittin pre-exposure. The percentage stimulation of adenylate cyclase by sodium fluoride or guanylylimidodi-phosphate was not significantly affected by activation of endogenous phospholipase A2 Phosphodiesterase activity in the soluble fraction of cell homogenates increased marginally (9%, P = 0.05) in cells exposed to melittin. These results suggest that activation of endogenous phospholipase A2 within the sarcolemma can modulate the activity of the beta adrenoceptor linked adenylate cyclase system of intact cardiac cells. The reduced beta adrenoceptor responsiveness of the cells appears to be primarily due to an alteration in coupling between the beta adrenoceptor and the guanine nucleotide binding protein component of the adenylate cyclase system and not between the latter and the catalytic subunit.
Keyword 3′,5′-cyclic AMP
Adenylate cyclase
Beta adrenoceptors
Melittin
Phospholipase A2
Phospholipids
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
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