Ion shifts in myocardial cells during ischemia and reperfusion and the effect of membrane stabilizing agents on ischemic ion transport.

Ischemia-and reperfusion-induced time dependent changes of the intracellular K+/K+i/, Na+/Na+i/ and Ca2+/Ca2+i/ concentrations were analyzed in isolated Langendorff guinea pig hearts. In the ischemic period evoked by complete perfusion stop of 25 min duration a rapid loss of K+ and gain of Na+ was found. Ca2+i concentration started to increase only after 15 min of global ischemia. Reperfusion did not evoke substantial changes during the first minutes however Ca2+i very rapidly increased after 7 minutes of reperfusion. K+i rapidly increased above initial values in the first 3 minutes of reperfusion but then suddenly declined to the lowest ischemic level and remained at this level. Na+i concentration elevated by ischemia was not further affected by reperfusion. The membrane stabilizing antiarrhythmic agents: quinidine and lidocaine proved to be effective in preventing or moderating ischemia induced shifts in K+i and Na+i concentrations however did not affect Ca2+i content. This latter was markedly reduced by verapamil, a substance which failed to influence ischemic shifts of K+i and Na+i content.