[Effect of systemic hematocrit on blood supply in microvessels of the cerebral cortex]

The rat systemic hematocrit was increased by 44-54% by means of substitution of 2 ml of the rat own blood with the same volume of washed erythrocytes. Cine-TV technique revealed that the linear velocity of blood flow decreased by 20% immediately after the erythrocytes administration in most vessels under study. Changes of the blood flow were different in some microvessels: in 89% of cases the velocity decreased by 100-1600 mu/sec; no changes occurred in 5% of cases; and in 6% of cases the velocity increased by 100-500 mu/sec. The above changes were followed by a drop of arterial pressure (118 and 107 mm Hg, resp.). Within 5 min after increase of the systemic hematocrit, the blood flow was practically restored followed by an increase in the arterial pressure even over initial values. The data obtained suggest that the systemic hematocrit plays a certain part in changes of the blood flow in microvessels, being not, however, a major factor.