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Impairment of β-receptor-adenylate cyclase coupling during long-term metabolic inhibition in cultured heart muscle cells
J Mol
Cell
Cardiol
pW16
IMPAIRMENT DF B-RECEPTOR-ADENYLATE CYCLASE COUPLING DURING LONG-TERM METABOLIC INHIBITION IN CULTURED HEART MUSCLE CELLS Bernhard Wagenknecht, Claudia Beuttler, Karl Werdan Medizinische Klinik I, Klinikum Grosshadern, University of Munich, F.R.G. Acute as well as chronic myocardial ischemia is associated with an altered responsiveness to catecholamines. To study whether long-term ATP depletion in cardiomyocytes could be responsible for these alterations, we exposed neonatal rat heart muscle cells to 5 mM deoxyglucose for 24 hours. This manipulation results in a reversible reduction of ATP content to 65 %. The number of 8-receotors falls to 82 % whereas the receptor-mediated CAMP-prod_lSction (stimulation with'lOmb M isoproterenol) is reduced bv 55 %. Forskolin (10 M) was used to studv receotor-independent. alterations o"f the adenylate cyclase iystem. In ATP-deaeted 'cells the forskolin-stimulated CAMP-production was attenuated by 90 %. Conclusion: 1. Cultured heart muscle cells are a suitable experimental model system to study receptor regulation during long-term metabolic inhibition. 2. Long-term ATP depletion in heart muscle cells results in an impairment of B-receptor-adenylate cyclase signaling due to alterations at the receptoras well as the postreceptor-level. Supported
PW17
22 (Supplement
III)
by DFG (We 1230/1-l)
(1990)
and
Friedrich-Baur-Stiftung.
DRUG EFFECTS ON cGMP-STIMULATED PHOSPHODIESTERASE FROM CARDIAC TISSUES Narcisse Komas, Claire Lugnier, Jean-Claude Stoclet. CNRS, URA 600. Facult6 de Pharmacie, Universit6 Louis Pasteur de Strasbourg, B.P. 24, 67401 lllkirch France It has been suggested that CAMP hydrolysis by a cGMP-stimulated phosphodiesterase (cGS-PDE) accounts for the antagonismbstween cGMP and &&IF in the regulation of cardiac mu&e conlraclilll~, but the c&urence and role of this enzyme are unknown in the pacemaker tissue. Activation of cGS-PDE by cGMP analogues and its inhibition by cardlltonic drugs and other PDE inhibitors have been investiiated on the enzyme, isolated by High Performance Liquld Chromatography, from the dog lefl ventricle and from a dog sinoatrial node enriched preparation. The resultsshownosignificantdifferenoebetweentheproperties and dtugsensltiiitiesof cGS-PDE from the two 1issues. cGMP itself. 8-br-cGMP and P’deoxy-cGMP had dual effects on cGS-PDE which coukf be related to interactllns with allosteric and catalytic sites: at low concentrations CAMP hydrolysis was stimulated (maximal effect respectively at 10 p.M, 100 pM and 100 l.tM), while at higher concentrations these compounds inhibited CAMP hydrolysis. Cardiitonic drugs (enoximcne, piroximone and milrlnone) and selective inhibitors of other PDE forms (zaprinast, sulmazole and rolipram) were not effective inhibitors of cGS-PDE, while IBMX and dipyrldamole were efficient inhibitors of this enzyme (in the HIM range) and were more potent in the presence than in the absence of cGMP. In conclusion: i) cGS-PDE is present in the dog sinoattial node as in the left ventricle, ii) &br-cGMP and P’deoxycGMP are less able than cGMP 10 induce the potent stimulation of cGS-PDE and, iii) the mechanism of the positive inotropic effect of oardiitonicdtugs probably does not involvetheinhibiiion of cGS-PDEin canine heart.
Cell
Cardiol
pW16
IMPAIRMENT DF B-RECEPTOR-ADENYLATE CYCLASE COUPLING DURING LONG-TERM METABOLIC INHIBITION IN CULTURED HEART MUSCLE CELLS Bernhard Wagenknecht, Claudia Beuttler, Karl Werdan Medizinische Klinik I, Klinikum Grosshadern, University of Munich, F.R.G. Acute as well as chronic myocardial ischemia is associated with an altered responsiveness to catecholamines. To study whether long-term ATP depletion in cardiomyocytes could be responsible for these alterations, we exposed neonatal rat heart muscle cells to 5 mM deoxyglucose for 24 hours. This manipulation results in a reversible reduction of ATP content to 65 %. The number of 8-receotors falls to 82 % whereas the receptor-mediated CAMP-prod_lSction (stimulation with'lOmb M isoproterenol) is reduced bv 55 %. Forskolin (10 M) was used to studv receotor-independent. alterations o"f the adenylate cyclase iystem. In ATP-deaeted 'cells the forskolin-stimulated CAMP-production was attenuated by 90 %. Conclusion: 1. Cultured heart muscle cells are a suitable experimental model system to study receptor regulation during long-term metabolic inhibition. 2. Long-term ATP depletion in heart muscle cells results in an impairment of B-receptor-adenylate cyclase signaling due to alterations at the receptoras well as the postreceptor-level. Supported
PW17
22 (Supplement
III)
by DFG (We 1230/1-l)
(1990)
and
Friedrich-Baur-Stiftung.
DRUG EFFECTS ON cGMP-STIMULATED PHOSPHODIESTERASE FROM CARDIAC TISSUES Narcisse Komas, Claire Lugnier, Jean-Claude Stoclet. CNRS, URA 600. Facult6 de Pharmacie, Universit6 Louis Pasteur de Strasbourg, B.P. 24, 67401 lllkirch France It has been suggested that CAMP hydrolysis by a cGMP-stimulated phosphodiesterase (cGS-PDE) accounts for the antagonismbstween cGMP and &&IF in the regulation of cardiac mu&e conlraclilll~, but the c&urence and role of this enzyme are unknown in the pacemaker tissue. Activation of cGS-PDE by cGMP analogues and its inhibition by cardlltonic drugs and other PDE inhibitors have been investiiated on the enzyme, isolated by High Performance Liquld Chromatography, from the dog lefl ventricle and from a dog sinoatrial node enriched preparation. The resultsshownosignificantdifferenoebetweentheproperties and dtugsensltiiitiesof cGS-PDE from the two 1issues. cGMP itself. 8-br-cGMP and P’deoxy-cGMP had dual effects on cGS-PDE which coukf be related to interactllns with allosteric and catalytic sites: at low concentrations CAMP hydrolysis was stimulated (maximal effect respectively at 10 p.M, 100 pM and 100 l.tM), while at higher concentrations these compounds inhibited CAMP hydrolysis. Cardiitonic drugs (enoximcne, piroximone and milrlnone) and selective inhibitors of other PDE forms (zaprinast, sulmazole and rolipram) were not effective inhibitors of cGS-PDE, while IBMX and dipyrldamole were efficient inhibitors of this enzyme (in the HIM range) and were more potent in the presence than in the absence of cGMP. In conclusion: i) cGS-PDE is present in the dog sinoattial node as in the left ventricle, ii) &br-cGMP and P’deoxycGMP are less able than cGMP 10 induce the potent stimulation of cGS-PDE and, iii) the mechanism of the positive inotropic effect of oardiitonicdtugs probably does not involvetheinhibiiion of cGS-PDEin canine heart.