Effect of intensified red blood cell aggregability on arterial pressure and mesenteric microcirculation.

Intensified aggregability of red blood cells (RBC) was produced in adult white rats by the step-by-step intravascular administration of a high-molecular-weight dextran, with a molecular weight approximating that of blood fibrinogen. As a result, the systemic arterial pressure was elevated by more than one-third of the initial level, whereas the diameter of arterioles in the intestinal mesentery remained practically unchanged. This provided sufficient grounds for the conclusion that the increase in the total peripheral resistance was due to disturbances in blood rheological properties. Despite the elevated arterial pressure, the blood flow velocity in mesenteric arterioles displayed a clear-cut tendency to slow down. Simultaneously, a large number of RBC aggregates appeared in the mesenteric microvessels. In patients with a stable form of arterial hypertension the RBC aggregability index was found to be significantly increased as compared with that of the healthy control group. Following treatment with Ca(2+)- and beta-adrenergic blockers the index decreased significantly in parallel with the lowering of arterial pressure. The obtained results suggest that the intensified RBC aggregation in microvessels causing a disturbance of normal blood flow structure, and hence of blood rheological properties, might be an important factor responsible for the elevation of systemic arterial pressure in humans with arterial hypertension.