Plasma and blood viscosities, and aggregation of red cells in racehorses.

Abstract

Nineteen racehorses have been studied for haemorheologic factors as earlier studies showed a definite correlation between physical fitness and these factors in humans. Results included individual values for all viscosity factors, and the arithmetic means, the latter showing 4.70 +/- 0.49 cP for blood viscosity measured at a shear rate of 180 s-1; 1.100 +/- 0.048 cP for plasma viscosity; 1.045 +/- 0.063 for the rigidity of red cells defined by term 'Tk'; 42.2 +/- 4.1% haematocrit; 290 +/- 39 mg per 100 ml for fibrinogen level; and 278 +/- 75 mm h-1 for aggregation of red cells at 37 degrees C (corrected for plasma viscosity and at constant haematocrit of 30%). Data for subgroups have also been obtained. Linear regressions of apparent blood viscosity against log shear rate were found to be specific to individual racehorses, and differed significantly between some racehorses. Data for blood viscosity, plasma viscosity and haematocrit were near the values reported for human athletes, but rigidity of red cells and aggregation of red cells was found to be much higher in horses. No correlation was found between aggregation of red cells and fibrinogen level. In blood samples from some horses, the erythrocyte sedimentation rates increased with decrease of temperature, while in other samples they increased with increase of temperature. It appears that it is possible to characterise individual horses by blood viscosity factors and viscosity functions.