title: Interaction between cyclic GMP protein kinase and cyclic AMP may be diminished in stunned cardiac myocytes.
abstract: We tested the hypothesis that the importance of the negative functional effects of the cyclic GMP protein kinase would be reduced in stunned (simulated ischemia/reperfusion) cardiac myocytes. Ventricular cardiac myocytes were isolated from New Zealand white rabbits (N=7). Myocytes were studied at baseline and after simulated ischemia (15 min of 95% N(2)-5% CO(2) at 37 degrees C) followed by simulated reperfusion (reoxygenation). Cell shortening was studied with a video edge detector; O(2) consumption was measured using O(2) electrodes. Protein phosphorylation was measured autoradiographically after gel electrophoresis. Functional and metabolic data were acquired after: (1) 8-(4-chlorophenylthio)guanosine-3',5'-monophosphate (PCPT, cGMP protein kinase agonist) 10(-7) or 10(-5) M; (2) 8-Br-cAMP 10(-5) M followed by PCPT 10(-7) or 10(-5) M; (3) beta-phenyl-1, N(2)-etheno-8-bromoguanosine-3',5'-monophosphorothioate, SP-isomer (SP, cGMP protein kinase agonist) 10(-7) or 10(-5) M; (2) 8-Br-cAMP 10(-5) M followed by SP 10(-7) or 10(-5) M. At baseline, percent of shortening (Pcs) and maximal rate of shortening (Rs) were significantly lower in the stunned myocytes (Pcs: 5.0+/-0.2% control vs. 3.8+/-0.3 stunned; Rs: 64.8+/-5.9 microm/s control vs. 46.9+/-4.8 stunned). In both groups, PCPT and SP dose-dependently decreased Pcs and Rs. The effects were slightly, but not significantly, less in stunned myocytes. 8-Br-cyclic AMP significantly increased function in control, but not stunned myocytes (Pcs, 4.5+/-0.5 to 6.2+/-0.8 control vs. 3.1+/-0.2 to 3.6+/-0.2 stunned). The negative functional effects of PCPT and SP were diminished after 8-Br-cyclic AMP in control (from -39% to-29%) and diminished significantly more in the stunned myocytes (-19%). PCPT and cyclic AMP phosphorylated similar protein bands. In stunned myocytes, three (22, 31 and 53 kDa) bands were enhanced less by PCPT.
authors.affiliation: Heart and Brain Circulation Laboratory, University of Medicine and Dentistry of New Jersey (UMDNJ), Robert Wood Johnson Medical School, Piscataway, NJ 08854-5635, USA.
authors.forename: L
authors.initials: L
authors.lastname: Yan
authors.forename: K N
authors.initials: KN
authors.lastname: Patel
authors.forename: Q
authors.initials: Q
authors.lastname: Zhang
authors.forename: P M
authors.initials: PM
authors.lastname: Scholz
authors.forename: H R
authors.initials: HR
authors.lastname: Weiss
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D048429:Cell Size / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017682:Myocardial Stunning / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects; D010750:Phosphoproteins / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D011817:Rabbits; D013873:Thionucleotides / Q000494:pharmacology
chemical_list: D010750:Phosphoproteins; D013873:Thionucleotides; C098740:8-bromo-beta-phenyl-1,N(2)-ethenoguanosine 3',5'-cyclic monophosphorothioate; D015124:8-Bromo Cyclic Adenosine Monophosphate; C055656:8-((4-chlorophenyl)thio)cyclic-3',5'-GMP; D000242:Cyclic AMP; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP