Functional alterations of human platelets following ¹¹¹In labeling with different ligands and incubation media

We studied the effects of various ¹¹¹In-water soluble chelates and incubation media on labeling efficiency of platelets and in vitro platelet aggregability. High labeling efficiency of platelets in ACD-saline was achieved with ¹¹¹In-oxine sulfate, ¹¹¹In-tropolone and ¹¹¹In-MPO (2-mercaptopyridine-N-oxide). In the condition with 4.8 x 10⁶/mm³ platelets in ACD-plasma, ¹¹¹In-oxine-sulfate had low labeling efficiency and inconsistent labeling, while ¹¹¹In-tropolone and ¹¹¹In-MPO had high labeling efficiency. In vitro platelet aggregability (ADP 2 μM) was reduced when platelets were labeled in the absence of plasma. However, there was no significant difference in platelet aggregability among ¹¹¹In-platelets labeled by three different chelates. In conclusion, to maintain aggregation activity of the platelets with relatively high labeling efficiency, the best result was obtained by using MPO or tropolone chelate in plasma at 4.8 x 10⁶/μl platelet concentration.