Histamine uptake by human platelets

We have investigated the uptake of histamine by human platelets. Incubations were carried out in platelet rich plasma prepared by using sodium citrate as an anticoagulant at histamine concentrations of 2.5 nmol.l^-1, with and without stirring, in a platelet aggregometer cuvette at 37 °C. Stirring increased platelet histamine uptake significantly. Conventional platelet aggregating agents (e.g. adrenaline) significantly increased platelet histamine uptake at sub-aggregatory concentrations. Histamine uptake by platelets may be a useful index of platelet behaviour when studying the effect of subaggregatory concentrations of platelet agonists in conditions where platelet aggregation is altered, e.g. peripheral vascular disease and diabetes mellitus.