Protective effect of a low K+ cardioplegic solution on myocardial Na,K-ATPase activity.

Long duration ischemia in hypothermic conditions followed by reperfusion alters membrane transport function and in particular Na,K-ATPase. We compared the protective effect of two well-described cardioplegic solutions on cardiac Na,K-ATPase activity during reperfusion after hypothermic ischemia. Isolated perfused rat hearts (n = 10) were arrested with CRMBM or UW cardioplegic solutions and submitted to 12 hr of ischemia at 4°C in the same solution followed by 60 min of reperfusion. Functional recovery and Na,K-ATPase activity were measured at the end of reperfusion and compared with control hearts and hearts submitted to severe ischemia (30 min at 37°C) followed by reflow. Na,K-ATPase activity was not altered after 12 hr of ischemia and 1 hr reflow when the CRMBM solution was used for preservation (55 ′ 2 μmolPi/mg prot/hr) compared to control (53 ′ 2 μmol Pi/mg prot/hr) while it was significantly altered with UW solution (44 ′ 2 μmol Pi/mg prot/hr, p<0.05 vs control and CRMBM). Better preservation of Na,K-ATPase activity with the CRMBM solution was associated with higher functional recovery compared to UW as represented by the recovery of RPP, 52 ′ 12% vs 8 ′ 5%, p<0.05 and coronary flow (70 ′ 2% vs 50 ′ 8%, p<0.05). The enhanced protection provided by CRMBM compared to UW may be related to its lower K + content.