THE ACCUMULATION OF ORGANIC BASES BY THE HUMAN PLATELET

¹ Departments of Medicine, Baltimore City Hospitals and the Johns Hopkins University School of Medicine, Baltimore, Maryland

Washed human platelets were incubated with reserpine, quinidine, procaine or histamine. Subsequently, the concentration of drug in cell water was measured. There was extensive binding of reserpine to the platelet over a wide range of reserpine concentrations. Uptake was considerably reduced when platelets were incubated in plasma or in a buffered solution of albumin rather than in buffer alone. Ultrafiltration experiments revealed the drug to bind avidly to plasma protein. Similarly, there was considerable binding of quinidine to the platelet. The cell/medium distribution ratio of quinidine was inversely proportional to the initial concentration of drug in the medium. The distribution of procaine and histamine across the membrane of the platelet, at an external pH of 6.8 or of 7.4, could be explained by the hydrogen ion gradient across the membrane. At an external pH of 8.0, these drugs were, in part, bound to the cell.