Platelet cryopreservation with glycerol, dextran, and mannitol: recovery of 5-hydroxytryptamine uptake and hypotonic stress response.

Human platelets were frozen in 0.5 M glycerol, 0.5 M glycerol + 3% Dextran T40, or 0.5 M glycerol + 5% mannitol. The recovery of active transport of 5-hydroxytryptamine (5-HT) and the hypotonic stress response after freezing were dependent on the rate of cooling: the optimum range of rates was between 12 and 23 degrees C/min. The numerical recovery of cells was independent of cooling rate, but freezing altered the cell-size distribution. The combination of dextran and glycerol was no better than glycerol alone at protecting platelets against freezing damage. Mannitol, however, adversely affected platelet 5-HT uptake, and this was reflected in a low recovery of that activity after freezing platelets in glycerol supplemented with mannitol.