Binding of 113mIn ion to human erythrocytes.

The 113mIn ion is tightly bound to hemoglobin; less than 20% of the total amount of 113mIn present in the red cells are attached to the stroma. The extraction of the heme from purified hemoglobin with HCl/acetone mixture showed 99% of the 113mIn activity in the heme fraction. In comparison to the 51Cr and 99mTc isotopes known to be bound to the beta-chain of globin only, 20 and 30%, respectively, of their activities were found in the heme fraction. Acetyl acetone is necessary for effective labelling of erythrocytes with 113mIn. Only 7% of the acetyl acetone applied were found in the cells associated with the heme. It is not involved in the binding of 113mIn to hemoglobin, but facilitates the transport of the 113mIn ions into the cells.