Shape transformation of erythrocytes determined by light scattering changes associated with relaxation of particle orientation.

Dilute suspensions of normal erythrocytes exhibit a pearl-like sheen (nacre) when subjected to flow. This results from the asymmetric form (biconcave disc) of these cells. Upon cessation of flow, the nacreous effect decays in 2-3 min, corresponding to the time required for the discs to achieve random orientations by rotatory Brownian motion. The degree of nacre can be measured by comparing the intensity of scattered red light at an angle of 45 degrees for the flowing system to that when the effect has disappeared. Since the phenomenon is critically dependent on red cell shape, it is possible to quantify the extent of erythrocyte disc-to-sphere transformation induced by detergents, low salt concentrations, or metabolic depletion.