Cyclic GMP reduces ventricular myocyte stunning after simulated ischemia-reperfusion.
We tested the hypothesis that the second messenger activated by nitric oxide, cyclic GMP, would reduce the effects of myocyte stunning following simulated ischemia-reperfusion and that this was related to cyclic GMP protein kinase. Ventricular cardiac myocytes were isolated from New Zealand White rabbits (n = 8). Cell shortening was measured by a video edge detector and protein phosphorylation was determined autoradiographically after SDS gel electrophoresis. Cell shortening data were acquired at: (i) baseline followed by 8-Bromo-cGMP 10(-6) M (8-Br-cGMP) and then KT 5823 10(-6) M (cyclic GMP protein kinase inhibitor) and (ii) simulated ischemia (20 min of 95% N(2)-5% CO(2) at 37 degrees C) followed by simulated reperfusion (reoxygenation) with addition of 8-Br-cGMP 10(-6) M followed by KT 5823 10(-6) M, (iii) addition of 8-Br-cGMP prior to ischemia followed by the addition of KT 5823 10(-6) M after 30 min of reoxygenation. In the control group, 8-Br-cGMP 10(-6) M decreased percentage shortening (%short) (5.0 +/- 0.6 vs 3.8 +/- 0. 4) and the maximum velocity (V(max), microm/s) (48.6 +/- 6.9 vs 40.2 +/- 6.4). KT 5823 10(-6) M added after 8-Br-cGMP partially restored %short (4.6 +/- 0.5) and V(max) (46.6 +/- 8.0). After stunning, baseline myocytes had decreased %short (3.4 +/- 0.2) and V(max) (36. 0 +/- 4.2). After the addition of 8-Br-cGMP, the %short (2.7 +/- 0. 2) and V(max) (27.6 +/- 2.5) decreased further. The addition of KT 5823 did not change either the %short or the V(max). The myocytes with 8-Br-cGMP during ischemia had increased %short (4.2 +/- 0.2) and V(max) (37.2 +/- 3.4) when compared to the stunned group. The addition of KT 5823 did not significantly alter %short (3.3 +/- 0.4) or V(max) (29.2 +/- 5.0) in the myocytes pretreated with 8-Br-cGMP. Protein phosphorylation was increased by 8-Br-cGMP in control and stunned myocytes. KT 5823 blocked this effect in control but not stunned myocytes, suggesting some change in the cyclic GMP protein kinase. Ischemia-reperfusion produced myocyte stunning that was reduced when 8-Br-cGMP was added prior to but not after ischemia.
Gandhi
A
A
Heart and Brain Circulation Laboratory, Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, New Jersey, 08854-5635, USA.
Yan
L
L
Scholz
P M
PM
Huang
M W
MW
Weiss
H R
HR
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002227:Carbazoles; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006352:Heart Ventricles; D007211:Indoles; D017202:Myocardial Ischemia / Q000503:physiopathology*; D015425:Myocardial Reperfusion; D017682:Myocardial Stunning / Q000503:physiopathology*; D009206:Myocardium / Q000166:cytology*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011817:Rabbits
D000470:Alkaloids; D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D010750:Phosphoproteins; C073601:KT 5823; C016276:8-bromocyclic GMP; D006152:Cyclic GMP