[Mechanism of myocardial protection with potassium arrest in isolated ischemic rat hearts].
Isolated working rat hearts were exposed to 25 min ischemia, and functional recovery was assessed by aortic flow (AoF) and rate-pressure product (RPP) to evaluate the beneficial effects of potassium (20 mM) induced arrest (K-arrest) prior to ischemia. K-arrest improved the recovery of function after 30 min of reperfusion compared with the control group (%AoF: 68 +/- 6 vs 0%, %RPP: 90 +/- 3% vs 60 +/- 3%, p less than 0.01). The accumulation of Ca++ at the end of reperfusion was less in hearts with K-arrest (2.2 +/- 0.1 vs 4.5 +/- 0.3 mumol/g dry, p less than 0.01). There was no difference between the two groups in high energy phosphate content at the end of ischemia. The increase in intracellular Na+ (Nai) during ischemia was reduced in hearts with K-arrest (delta: 19 vs 46 mumol/g dry), and the level of intracellular K+ (Ki) was higher at the end of ischemia in hearts with K-arrest (341 +/- 4 vs 318 +/- 2 mumol/g dry, p less than 0.01). During the first 5 min of reperfusion, the level of Ki in K-arrested hearts jumped to a higher level than in the control group (delta: 15 vs 2 mumol/g dry, p less than 0.01). The level of Nai was lower in hearts with K-arrest after 5 min of reperfusion. These data suggested that K-arrest might preserve the activity of Na+/K+ ATPase during ischemia and early reperfusion, and that it attenuated the increase in Nai during ischemia and reperfusion, which resulted in less Ca++ overload during reperfusion via the Na+/Ca++ exchange mechanism and led to improved recovery.
Yoshino
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Sigfied and Janet Weis Center for Research, Geisinger Clinic.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D003327:Coronary Disease / Q000378:metabolism; D006324:Heart Arrest, Induced / Q000379:methods*; D066298:In Vitro Techniques; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000517:prevention & control*; D009206:Myocardium / Q000378:metabolism*; D011188:Potassium; D017680:Potassium Compounds; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D017680:Potassium Compounds; C018369:potassium cardioplegic solution; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; D002118:Calcium