Myocardial stunning is associated with impaired calcium uptake by sarcoplasmic reticulum.
Myocardial stunning (temporary post-ischaemic contractile dysfunction) may be caused by oxidative stress and/or impaired myocyte calcium homeostasis. Regional myocardial stunning was induced in open-chest pigs (segment shortening reduced to 68.3+/-4.7% of baseline) by repetitive brief circumflex coronary occlusion (I/R). Reduced glutathione was depleted in stunned myocardium (1.34+/-0.06 vs. 1.77+/-0.11 nmol/mg, p=0.02 vs. remote myocardium) indicating regional oxidant stress, but no regional differences were observed in protein-bound 3-nitrotyrosine or S-nitrosothiol content. Repetitive I/R did not affect myocardial quantities of the sarcolemmal sodium-calcium exchanger, L-type channel, SR calcium ATPase and phospholamban, or the kinetics of ligand binding to L-type channels and SR calcium release channels. However, initial rates of oxalate-supported (45)Ca uptake by SR were impaired in stunned myocardium (41.3+/-13.5 vs. 73.0+/-15.6 nmol/min/mg protein, p=0.03). The ability of SR calcium ATPase to sequester cytosolic calcium is impaired in stunned myocardium. This is a potential mechanism underlying contractile dysfunction.
Kumar
Sanjay
S
National Heart & Lung Institute, Imperial College, London, UK. S.Kumar3@rbht.nhs.uk
Hall
Roger J C
RJ
Mani
Ali R
AR
Moore
Kevin P
KP
Camici
Paolo G
PG
Rimoldi
Ornella E
OE
Williams
Alan J
AJ
Macleod
Kenneth T
KT
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D006439:Hemodynamics; D009200:Myocardial Contraction; D017202:Myocardial Ischemia / Q000378:metabolism* / Q000503:physiopathology; D009206:Myocardium / Q000378:metabolism*; D026361:Reactive Nitrogen Species / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism*; D013552:Swine
D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium