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 ischeamic 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.