Osmotic stress as a factor in the detrimental effect of glycerol on human platelets.

The aim of this work was to determine the importance of osmotic stress as a damaging factor in the detrimental effect of glycerol on human platelets. The severity of osmotic stress was mitigated by reducing the rate of change of glycerol concentration in the suspending medium. The classical permeability equations were used to predict cell volume changes in response to step changes in extracellular glycerol concentration. Protocols were devised that limited cellular shrinkage during glycerol addition and cellular swelling during glycerol dilution. When glycerol was added and diluted rapidly, the recovery of the hypotonic stress response with respect to untreated controls was unaffected by 0.25 mol/liter glycerol, but was reduced to ca. 65% after exposure to 0.5 mol/liter glycerol and to ca. 25% after exposure to 1 mol/liter glycerol. When 1 mol/liter glycerol was added and removed slowly such that cell volume remained within the range of 60-130% of normal volume, recovery of the hypotonic stress response was improved to ca. 50%, and the aggregation response was undiminished. Osmotic stress was therefore at least partly responsible for the damage caused by glycerol. However, platelets were damaged more after slow dilution from 1 mol/liter glycerol, when cellular swelling was limited to 116% of normal volume, than after rapid dilution from 0.25 or 0.5 mol/liter glycerol, which resulted in cellular swelling to 123% and 146% of normal volume, respectively. Thus, a possible toxic effect of glycerol cannot as yet be discounted.