Effect of reduced red cell "deformability" on flow velocity in capillaries of rat mesentery.

A graded reduction of "deformability" of red blood cells (RBC's) of rats was obtained by treatment with the SH-oxidizing agent, diamide. Rigidified RBC's were injected into rats by isovolemic exchange against 60% of the native RBC's and RBC flow velocities in capillaries of rat mesentery measured. At normal mean arterial pressure RBC flow velocity decreases by 29% in rats receiving cells rigidified with 0.5 mmol . 1(-1) diamide. Surprisingly a further rigidification of erythrocytes by 1.5 mmol . 1(-1) diamide results in a decrease of flow by only 15%. During hypotension RBC flow velocities dropped precipitously to 8 +/- 15% for the 0.5 nmol . 1(-1) and to 2 +/- 6% for the 1.5 mmol . 1(-1) diamide group compared to velocities during normotension. By microscopy we observed a stop of flow in many vessels. This result outlines the importance of a normal red cell "deformability" for the maintenance of sufficient perfusion of the microcirculation, in particular at low blood pressure gradients.