Microrheology in skeletal muscle vessels of erythrocytic mice [article]

Vincent Richter, Universitätsbibliothek Der FU Berlin, Universitätsbibliothek Der FU Berlin
2011
Elevated systemic hematocrit (Hct) is known to increase cardiovascular risk, such as deep vein thrombosis, myocardial infarction, and stroke. Besides an impairment of the hemodynamic conditions due to the increased blood viscosity and resistance to blood flow, another possible mechanism could be a disturbance of the blood-endothelial cell (EC) interface. It has been shown that the flowing blood interacts with the EC surface via an approximately 0.5 µm thick layer, termed glycocalyx, or
more » ... al surface layer (ESL), which is relevant for various physiological and pathophysiological processes, including inflammation, transendothelial molecular transport, and atherosclerosis. The consequences of increased Hct levels for the functional properties of this interface in microvessels are incompletely understood. To examine the effects of elevated Hct on ESL thickness, microvascular hemodynamics and hemorheology, an erythropoietin-transgenic mouse line (tg6) exhibiting Hct levels as high as 0.85 without alteration of total peripheral resistance was used. Intravital microscopy of cremaster muscle venules (nvessel = 32), both before and after systemic hemodilution, was combined with micro-particle image velocimetry (µ-PIV) to determine specific flow quantities (flow velocity, shear rate, shear stress, viscosity, flow rate) and ESL thickness. C57 wild-type mice (wt, Hct 0.46) served as control (nvessel = 37). A flow simulation model was used to assess the effects of changes in Hct and ESL on overall flow resistance in a microvascular network. Tg6 mice showed reduced flow velocity (2.5-fold) and flow rate (2-fold) relative to their wt counterparts. ESL thickness in tg6 mice was substantially smaller (median, 0.13 µm) than in control mice (median, 0.52 µm). Flow simulations show that the increase in luminal vessel diameter in tg6 mice due to the reduced ESL accounts for less than 20% of the maintenance of network flow resistance. The simulations further indicate that only the integrative effect of several compensatory mecha [...]
doi:10.17169/refubium-15771 fatcat:grzdmnsvbffurg6kildmkzfwye