Erythrocyte velocity and fluorescein transit time in the cerebral microcirculation of macroglobulinemic mice: Differential effect of a hyperviscosity syndrome on the passage of erythrocytes and plasma

Macroglobulinemic mice provide a model of human macroglobulinemia. These animals have an increased plasma viscosity, but whole blood viscosity may be normal because of anemia. In the cerebral microcirculation of these animals plasma velocity was significantly retarded, as indicated by prolonged arteriolarvenular transit time of fluorescein observed in microcineangiograms of the pial vasculature. On the other hand, erythrocyte velocity measured by ultra high-speed microcinematography was usually within normal limits, or elevated. Dehydration, a procedure which increases the concentration of macroglobulin, and increases the viscosity of whole blood and plasma, significantly decreased the erythrocyte velocity. The data are consistent with our previously published studies of "hyperviscosity syndromes" in that plasma transit time was prolonged to a greater extent than the erythrocyte velocity. Plasma velocity appears to diminish in the presence of increased plasma viscosity, even in the absence of an increased whole blood viscosity. On the other hand, erythrocyte velocity, while it may be influenced by plasma viscosity, seems to be more strongly influenced by additional factors such as hematocrit.