Erythrocyte aggregation tendency and cellular properties in horse, human, and rat: a comparative study.

Horse blood has a higher tendency to form red blood cell (RBC) aggregates compared with human blood, with this enhanced aggregation previously attributed to differences in plasma factors. Our results confirm this observation and further indicate that washed horse RBC also have a significantly higher aggregation tendency in dextran 70 solutions (i.e., horse RBC have a higher "aggregability"). In contrast, the aggregation tendency of rat RBC, both in autologous plasma and in dextran 70, is significantly less compared with human and horse RBC. Other rheological findings for horse and rat RBC include smaller changes in RBC deformation indexes over the same shear stress range and a lower RBC shape recovery time constant. Rat RBC also had higher two-phase aqueous polymer partition coefficients, suggesting a higher surface charge. Membrane protein analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed marked differences: 1) band 4.2 protein was lacking in horse RBC membranes, and 2) carbohydrate groups have different distributions in human, rat, and horse RBC, as indicated by different patterns in periodic acid-Schiff-stained protein bands. Our results clearly indicate significant differences in RBC aggregability among the three species and indicate that cellular factors contribute importantly to these differences. Furthermore, they suggest that systematic studies of blood and RBC from different species should provide insight into the mechanism(s) of RBC aggregation.