EXPRESSION OF CALCIUM REGULATORY PROTEINS IN SHORT-TERM HIBERNATION AND STUNNING IN THE IN-SITU PORCINE HEART

Background: Myocardial hibernation and stunning are characterised by a reversible contractile dysfunction during and after ischaemia, respec tively. Calcium homeostasis might be disturbed in hibernation and stun ning due to altered expression of cardiac proteins involved in calcium handling. Methods: In enflurane-anaesthetised swine the coronary bloo d flow through the left anterior descending coronary artery was decrea sed to reduce regional contractile function (microsonometry) by simila r to 50%. In transmural biopsies obtained during ischaemia and reperfu sion creatine phosphate as well as the expression of sarcoplasmic reti culum calcium ATPase (SERCA), phospholamban (PLB), calsequestrin (CSQ) ; and troponin inhibitor (TnI) were determined. Results: During ischae mia creatine phosphate, after an initial reduction, recovered back to control values, and necrosis was absent (hibernation). After 90 min of ischaemia the myocardium was reperfused for 120 min but regional cont ractile function continued to be depressed (stunning). PLB, SERCA, CSQ , and TnI proteins were unchanged during ischaemia as well as reperfus ion. Likewise, levels of PLB and SERCA mRNAs were unchanged. Conclusio n: It is concluded that other mechanisms than altered expression of th ese regulating proteins underlie the contractile dysfunction observed during acute ischaemia, short-term hibernation and stunning. (C) 1998 Elsevier Science B.V.