Effects of red blood cell hyperaggregation on the rat microcirculation blood flow

Abstract

This study presents the effects of red blood cell (RBC) hyperaggregation on the blood flow and pressure in the rat mesentery and cremaster network. We exclusively studied in situ non-vasodilated organs, in order to maintain the physiological regulation mechanisms. Dextran 500 was injected at different concentrations to increase RBC aggregation. The aggregation rate was measured on very small blood samples with an erythroaggregameter (SEFAM) which evaluated the disaggregating shear stress (tau D) needed to break the RBC aggregates. Microscopic observations and laser Doppler velocimetry were used to quantify the flow rate. The plasmatic dextran concentration (C) increase had different correlated effects: for example, tau D increased from 3 dynes cm-2 (for the control sample) to 14 dynes cm-2 (for C = 75 microM L-1); the flow rate was reduced threefold and very large aggregates were observed in the venules; the arteriolar pressure increased while venular pressure decreased. In order to differentiate the effects of RBC hyperaggregation from those of plasma hyperviscosity (due to dextran 500) on microcirculatory blood flow, we injected an RBC antiaggregating drug (troxerutine) (50 or 100 mg kg-1 i.v.). The consequences were a high reduction for (tau D) (from 14 dynes cm(-2)-9 dynes cm-2), smaller aggregates and higher blood flow in the venules. No effect of troxerutine was observed on plasma viscosity (plasma control: 1.9 cP with or without troxerutine; plasma with dextran at C = 75 microM L-1: 2.45 cP with or without troxerutine). The results strongly suggest that RBC aggregation has a significant influence on blood flow rate in the microcirculatory network.

Nitric oxide generation by endothelial cells exposed to shear stress in glass tubes perfused with red blood cell suspensions: role of aggregation

“…Most previous studies on the effects of RBC aggregation on in vivo blood flow dynamics have utilized models based on including or infusing highmolecular-weight material such as dextrans in the suspending medium (6,18,33). This approach results in increased suspending phase viscosity in addition to enhanced RBC aggregation (e.g., the Dextran group).…”

Modulation of endothelial nitric oxide synthase expression by red blood cell aggregation

“…In previous studies designed to assess the hemodynamic effects of RBC aggregation, high-mass-weight polymers such as 500-kDa dextran have been used to increase RBC aggregation (6,11,19,35,48). The use of these large polymers has been proven to be effective for modifying RBC aggregation, yet has potential disadvantages: 1) plasma or suspending phase viscosity is increased [e.g., for 500-kDa dextran, 1.5 g/dl yields a 80% increase of suspending medium viscosity (43)] and hence the fluid viscosity near the vascular wall is modified; 2) plasma proteins are diluted via the added polymer solution; 3) in some experimental animals (e.g., the rat), dextran and similar polymers can lead to anaphylactic-type reactions and thus induce a pathophysiological state (10); 4) the elevated colloid osmotic pressure caused by macromolecules in solution could alter intra-versus extravascular fluid volumes; and 5) due to metabolism/excretion, polymer concentration decreases with the time after infusion (22), thus precluding long-term temporal studies of RBC aggregation effects.…”

Red Blood Cell Aggregation and Deformability among Patients Qualified for Bariatric Surgery

“…7 Another study also confirmed the influence of the RBC hyperaggregability on the microcirculation blood-flow. 8 Other authors suggest that an increase in RBC aggregation influences venous vascular resistance 9 and predisposes to circulary stasis 10 and thrombosis. 11 The aim of this study was to investigate red blood cell aggregability and deformability among obese patients who were qualified for bariatric surgery and its correlation with lipid plasma concentrations.…”