Experimental regional myocardial ischaemia and myocardial uptake of potassium analogues; intercomparison of 42K, 86Rb and 201Tl

The uptake of 42K, 86Rb and 201Tl by non-ischaemic and ischaemic myocardium was determined in rats with coronary artery ligature lasting 10, 30, 60 and 120 min, and in control rats without ischaemia. Whereas the myocardial concentration of 201Tl and 42K in control rats was similar and higher than that of 86Rb, 201Tl was superior to the other two radionuclides due to its significantly higher accumulation in non-ischaemic myocardium and the higher ratio of non-ischaemic to ischaemic radioactivity. The 86Rb accumulation in non-ischaemic myocardium and non-ischaemic/ischaemic ratio began to decrease from its maximum at 10 min. 201Tl, 42K and 86Rb blood levels in intact animals decreased rapidly after intravenous injection to low and nearly stabilized values at 5 min. Na+K+-ATPase activity in the ischaemic myocardium was high in the acutely ischaemic myocardium and decreased to below control levels after 4 h of ischaemia; changes in activity could not influence the low uptake of potassium analogues in fresh ischaemic myocardium.