IN-111 TROPOLONE, A NEW HIGH-AFFINITY PLATELET LABEL - PREPARATION AND EVALUATION OF LABELING PARAMETERS

Abstract

Platelets were labeled with a new neutral, lipid-soluble metal complex of 111In and tropolone. Unlike oxine, which must be dissolved in ethyl alcohol, tropolone is soluble in isotonic saline. Platelet labeling with 111In tropolone can be performed in both acid-citrate-dextrose(ACD)-plasma and ACD-saline media within 2 h. Labeling efficiency was 80-90% in ACD-saline and 60-70% in the ACD-plasma medium. Optimum concentrations for the labeling of platelets with 111In tropolone were 5 .mu.g/ml in ACD-saline and 10 .mu.g/ml in ACD-plasma, using a 15 min incubation at room temperature. A kit formulation for convenient routine preparation of 111In labeled platelets was developed. Platelet labeling parameters studied were: concentration of tropolone, citrate, plasma proteins and Ca+2, platelet density, temperature and pH of incubation medium. Their effects on the mechanism of platelet labeling with lipid-soluble tracers are discussed.