Blood cell structure-function studies: light transmission and attenuation coefficients of suspensions of blood cells and model particles at rest and with stirring.

The Beer-Lambert law of light transmission was found valid for suspensions of blood platelets, erythrocytes, and leukocytes, as well as similarly sized model particles (latex spheres and flat guanine crystals), for a DB-G double-bean photometer at 605 and 710 mg, and a Payton aggregometer with red filter (660 to 750 mu). Attenuation coefficients (K) showed a similar dependence on a particle "equivalent sphere" radius as data reported for a "zero-degree photometer," for particles at rest. Size distribution, degree of aggregation, state of contamination, and effects of aldehyde fixation of the cell suspensions, well as optical geometry, were related to the measured K values. Particle optical efficiencies (K) for asymmetric particles were similar whether calculated from cross-sectional areas derived from "equivalent spheres" or from geometric cross-sections accounting for orientation distributions at rest. Appropriate cell and latex models were identified for the erythrocytes (E) and platelets (P) at rest on the basis of similar K,k values. The biphasic change in K occurring with stirring of these asymmetric blood cells (E, HP) was partly explainable by the known variations of K with shear-induced particle alignment to the optic axis. No such effects were observed with spherical particles or "sphered" cells, even when polydisperse as to size an aggregates. This investigation begins to quantitate ongoing light transmission studies of blood cell shape/aggregation changes.