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Platelet aggregation induced by ADP and collagen and five parameters of blood coagulation and fibrinolysis, (levels of fibrinogen, fibrinolytic activity of euglobulin, fibrinogen and/or fibrin degradation products, antiplasmin activity and antithrombin activity) were measured in patients with cancer of the head and neck. The results were compared with those from healthy controls. Enhancement of platelet aggregation, hyperfibrinolysis and hypercoagulable state were found in the circulatory blood of patients with cancer of the head and neck.

Earlier results indicated a diminished labelling efficiency and recovery negatively linked to actual cholesterol and lipoprotein values in hyperlipoproteinemics. This study was designed to examine whether other alternative tracers exhibit similar results and to study the influence on platelet viability in the presence or absence of PGI2. We demonstrate that no substantial difference occurs between the four tracers concerning labelling efficiency and recovery in normo- and hypercholesterolemics. Cholesterol severely affects the labelling parameters for all the tracers to a comparable extent. The absolute platelet function varies considerably, however, the percent changes in normo- and hypercholesterolemics seen before and after the labelling procedure do not differ significantly. PGI2 improves recovery in general, however, without affecting labelling efficiency or in vitro viability testing. As prolonged incubation further increases labelling efficiency, the presence and extent of hyperlipoproteinemia should be known in order to avoid poor labeling and viability and subsequently poor clinical results.

Platelet membranes play a key role in all stages of the haemostatic mechanism. Four of these in particular are considered here: adhesion to subendothelium, which involves an interaction between the glycoprotein I complex in the platelet membrane (deficient in the Bernard-Soulier syndrome) and plasma factor VIII; aggregation, involving the membrane glycoprotein IIb/IIIa complex (deficient in thrombasthenia), plasma fibrinogen and divalent cations; platelet factor 3 availability, a function of surface membrane phospholipids; and thromboxane synthesis, a function of the phospholipids of the membrane of the dense tubular system. The glycoprotein I complex also carries binding sites for thrombin and for drug-dependent antibodies, and glycoprotein IIb/IIIa is the site of the P1A1 antigen and of alpha-actinin.

Human platelets were labelled with aqueous 111In-tropolonate in comparison with 111In-oxinate. In normals the labelling efficiency with 111In-tropolonate was higher (93% +/- 2%) than with 111In-oxinate (67% +/- 8%) (P less than 0.05). In cases of severe thrombocytopenia, lower labelling efficiencies were obtained. In six normals a mean platelet life of 9 days +/- 3 days and an initial recovery of 59% +/- 15% were obtained. In twelve patients with thrombocytopenia the mean platelet life was 4 days +/- 4 days and the initial recovery was 58% +/- 20%. The absolute uptake of radioactivity in spleen and in liver in both groups are reported.