Enhancement of erythrocyte sedimentation rate by polymerized hemoglobin

Development of hemoglobin-based blood substitutes requires the scrutiny of blood rheological parameters that could be influenced by this class of molecules. Accordingly, we have examined the effects of glutaraldehyde-polymerized human hemoglobin on the erythrocyte sedimentation rate (ESR). For this purpose, human hemoglobin (Hb) was polymerized by glutaraldehyde, and its progress was monitored by gel permeation. ESR was measured by addition of hemoglobin or polymerized Hb (Poly-Hb) to citrated rat whole blood. The results indicate that, whereas Hb exerted minimal perturbation of ESR, Poly-Hb obtained under some polymerization conditions induced an over fifty-fold elevation of ESR. When polymerized Hb was fractionated by size, and different fractions were tested for their effects on ESR, a sharp dependence of ESR enhancement on molecular size of polymerized Hb was found. These observations suggest that ESR enhancement is mediated by macromolecular bridging formed by Poly-Hb of an adequate length between the surfaces of two stacking erythrocytes.