Interaction between cyclic GMP protein kinase and cyclic AMP may be diminished in stunned cardiac myocytes.
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.
Yan
L
L
Heart and Brain Circulation Laboratory, University of Medicine and Dentistry of New Jersey (UMDNJ), Robert Wood Johnson Medical School, Piscataway, NJ 08854-5635, USA.
Patel
K N
KN
Zhang
Q
Q
Scholz
P M
PM
Weiss
H R
HR
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
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