Mechanically stimulated ATP release and hemolysis. Inset: The amount of ATP (fmol/106 cells) detected in supernatants depends on the duration of mechanical shear stress stimulation. Each bar represents the average of 6 measurements ± SEM. The data on stimulated release are significantly different from control values (P < .05, Mann-Whitney U test, indicated by *). The main graph shows tight, linear correlation (R = 0.923; P < .0001) between ATP release induced by shear stress and extent of hemolysis (depicted as absorbance – left axis, or % hemolysis – right axis) for all data points (n = 30) of the experiment reported in the inset. Open symbols refer to the controls and solid symbols to stimulated RBC samples. The slope of linear fit corresponds to intracellular ATP concentration of 0.67 mM. The data are representative of n = 4 similar experiments. The estimated volume averaged shear stress was ∼4 dyne/cm2 (see “Materials and methods”).
