Earlier observations of ours have suggested that, under in vitro conditions resembling those under which platelets function haemostatically in vivo, their activation is promoted by the red cells. Seme of the evidence suggested that this is through limited haemolysis with release of ADP. However, newly determined time relationships make this uncertain. Could red cells provide ADP without haemolysis?Crtheir flow properties affect the process more? To analyse the problem, we are determining

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... nce of red cell deformability on membrane constitution; and release of haemoglobin and adeninenucleotides under different conditions. Ten percent human red cell suspensions in physiological salines flow under constant pressures through 2, 3, 4 and 5 pm micropore filters, the flow rate measured continuously with an electronic balance. Initial flow rates are increased by fluidising agents, eg. ethanol, and decreased by agents with opposite effect. Our results are consistent with the new hypothesis of S.J. Singer on the mode of action of amphipathic agents, such as chlorpromazine, on red cell membranes.