Enhancement of calcium cycling by atrial sarcoplasmic reticulum after cardiopulmonary bypass and cardioplegia during open heart surgery.
We studied myocardial Ca2+ cycling during cardiopulmonary bypass and cold-blood cardioplegia ( CPB/CBC) in patients with coronary heart disease undergoing coronary artery bypass grafting. Right atrial biopsies were taken from 13 patients before and after CPB/CBC: after pericardiotomy, immediately after aortic cross-clamp removal, and following termination of CPB/CBC. Changes in ionized Ca2+ concentration (nM) were monitored with indo 1 during Ca2+ uptake and Ca2+ release by sarcoplasmic reticulum in a medium containing 1% homogenized myocardium. Ryanodine inhibition was used to estimate Ca2+ release channel activity. With CPB/CBC, the initial Ca2+ concentration of reaction media increased 33%, (962 +/- 150 to 1262 +/- 106 nM; mean +/- SD). Ca2+ cycling increased asymmetrically, 108% for Ca2+ uptake (3.91 +/- 1.32 to 8.15 +/- 3.17 nM/s), 197% for Ca2+ release (0.90 +/- 0.80 to 2.73 +/- 1.13 nM/s), and 68% for the ratio of Ca(2+)-release to Ca(2+)-uptake activities (0.22 +/- 0.14 to 0.37 +/- 0.13). The dissociation constant of the Ca2+ pump for Ca2+ was unaltered by CPB/CBC (289 +/- 76 nM). During the time period that was studied post-bypass, Ca(2+)-pump activity remained increased, although the Ca(2+)-channel activity returned to pre-bypass values (all p < 0.05). We conclude that CPB/CBC produces increased myocardial Ca2+ load, twofold increased Ca2+ uptake, and threefold increased Ca2+ release by sarcoplasmic reticulum.[1]References
- Enhancement of calcium cycling by atrial sarcoplasmic reticulum after cardiopulmonary bypass and cardioplegia during open heart surgery. O'Brien, P.J., Shen, H., Ianuzzo, S., Cane, M.E., McGrath, L.B., Ianuzzo, C.D. Can. J. Physiol. Pharmacol. (1997) [Pubmed]
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