Capillary resistance to flow of hardened (diamide treated)red blood cells (RBC)

Pressure-flow curves for control and hardened (diamide treated) human RBC's were obtained in capillaries of the isolated rat mesentery, in order to evaluate resistance to flow of hardened RBC's. Blood vessels were maximally dilated by an infusion of 10(-5) mol/l acetylcholine and isoprenaline and perfused with freshly collected human RBC's as well as with RBC's hardened by a treatment (hct 40%; pH 8.0; 37 degree C) with 0.5 mmol/l or 1.5 mmol/l diamide, respectively, suspended in Albumin (0.05%) - Ringer solution. The mesentery was perfused via a hydrostatic pressure reservoir. Arterio-venous pressure difference was varied from 4-10 kPa, and corresponding arteriolo-venular pressure gradients changed from about 200-500 Pa/mm. No significant difference in resistance to flow was observed between control and diamide treated cells over the whole pressure range. However, the flow through the microvascular bed was inhomogeneous upon perfusion with diamide treated cells, caused by a deceleration and stoppage of the cells at capillary narrowing (ratio of cell to vessel diameter greater than 2). The time of stagnation increased with decreasing pressure gradient.