Influence of plasma proteins on erythrocyte aggregation in three mammalianspecies

The aggregation capacity of human erythrocytes lies between that of the non -aggregating bovine erythrocytes and the remarkably aggregating equine ones . As the ability to aggregate is attributed to cell factors and the composi tion of the plasma proteins, the role that plasma proteins play in the aggr egation process in these three species was studied. Washed erythrocytes wer e suspended in phosphate-buffered saline (PBS; pH 7.4, 300 mOsm/L) plus pol yvinylpyrrolidone (PVP) in a suitable concentration to obtain an average in tensity of aggregation (control media). The superimposed effect of replacin g 80% of the medium by either autologous plasma, serum or albumin solution was studied. The plasma proteins appeared to enhance aggregation by human a nd equine erythrocytes, but impaired this process in bovine erythrocytes. S ome evidence was obtained supporting the existence of serum factors capable of reducing aggregation of erythrocytes in cattle and it was concluded tha t the non-aggregating behaviour of bovine erythrocytes may be due to the ce lls interacting particularly with the macromolecules in the serum.