Affiliations: Zentrum Physiologie und Pathophysiologie, Georg - August Universität, Humboldtallee 23, 37073 Gottingen, Germany | Institut für Physiologie, Klinikum der RWTH Aachen, Pauwelsstraße 30, 52074 Aachen, Germany
Abstract: A Couette device was used for the examination of the flow behaviour exhibited by haemoglobin-A (Hb-A) solutions; the applied shear rates ranged from 0.624 x 10−3 through 4.59 s−1. The degree of O2 - saturation (SO2) was either above 90% (“oxyhaemoglobin-A” or OxyHb-A) or below 10% (“deoxyhaemoglobin-A” or DeoxyHb-A). Besides O2 ; K+, Ca2+ and 2,3-bisphosphoglycerate (2,3-BPG) were used as additional effectors of haemoglobin-A Thus, it has been possible to demonstrate: 1) The flow properties of OxyHb-A are strict Newtonian and are independent of any other effector added to the solutions. 2) The reduction of SO2 does not alter the linear torque - shear rate relationship as known for OxyHb-A. 3) K+ at 0.3 mmol/g DeoxyHb-A does not interfere with the Newtonian behaviour of DeoxyHb-A. 4) Ca2+ at 4 μmol/g DeoxyHb-A has no measurable influence on DeoxyHb-A rheology; at 24 μmol/g DeoxyHb-A, however, a fourfold rise in the viscosity of DeoxyHb-A was observed. 5) The addition of 2,3-BPG at fractions of 20 and 30 μmol/g DeoxyHb-A led to a 1.4 - fold increase in DeoxyHb-A viscosity for solutions with a DeoxyHb-A concentration below 32 g/100 ml; above 33 g/100 ml, however, the increase was 2.3 - fold if 2,3-BPG was present at the high relative concentration. 6) Microscopically, particle formation has been ascertained for the cases of increased viscosity in 4) and 5). This development of heterogeneity proved to be a reversible process on reoxygenation.
Keywords: human haemoglobin-A, polymerization, deoxygenation, viscometry, calcium, 2,3-bisphosphoglycerate, erythrocyte
