Erythrocyte aggregation as a determinant of blood flow: effect of pH, temperature and osmotic pressure

The effect of pH, temperature and osmotic pressure on velocity of erythrocyte aggregation was quantitatively examined with a rheoscope combined with a video-camera, an image analyzer and a computer, (a) in an artificial medium containing fibrinogen and albumin and (b) in diluted autologous plasma. (1) With increasing pH of the medium, the velocity of erythrocyte aggregation increased. (2) The velocity of erythrocyte aggregation in the artificial medium increased as the temperature rose. However, in 70% autologous plasma the velocity was minimum at 15-18 degrees C, increasing both above and below this temperature (above 30 degrees C, the velocity saturated). (3) The velocity of erythrocyte aggregation decreased in hypotonic medium, while it increased in hypertonic medium (at osmotic pressures higher than 400 mOsm, the velocity decreased). The mechanism of erythrocyte aggregation is discussed with special reference to the morphological changes produced by pH, temperature and osmotic pressure, and the implications of the phenomena for oxygen transport to tissues in (patho)physiological situations are considered.