Distribution of 201Tl in the blood.

Thallium-201 distribution in the blood was investigated both in vivo and in vitro. Thallium-201 was distributed into the erythrocytes and plasma with the ratio of 1.4 +/- 0.3 to 1.0, immediately after its administration. The uptake of 201Tl into the erythrocytes in vitro were affected by the incubation temperature and the presence of ouabain and KCl; indicating that the 201Tl was uptaken into cells partly through their membranes Na, K-ATPase. Erythrocytes could retain 201Tl in it, whereas 201Tl was present as free ion in the plasma. Thallium-201 was flew out of erythrocytes into the plasma, keeping the ratio of 201Tl in erythrocytes/plasma to be 1.9 +/- 0.2/1.0.