EFFECT OF ERYTHROCYTE DEFORMABILITY ON MYOCARDIAL HEMATOCRIT GRADIENT

Myocardial hematocrit gradient was determined between epicardium and endocardium of the left ventricular wall in rat heart under the influence of erythrocyte deformability alterations. Hematocrit determinations were performed by measuring two different radionuclides labeling plasma (I-125-labeled albumin) and erythrocytes (Tc-99m) in 100-mu m-thick left ventricular myocardium slices. Myocardial hematocrit gradient calculated after exchange transfusions with partially hardened red blood cell suspensions was compared with the results of the control group, in which the exchange transfusions were done using normal, hematocrit-matched blood. In the control group, the hematocrit value in the myocardium adjacent to epicardium was 0.331 +/- 0.076 l/l and decreased to 0.232 +/- 0.054 l/l near the endocardium. Myocardial hematocrit between these two was represented by a linear gradient. In the group with impaired erythrocyte deformability, the hematocrit value was 0.359 +/- 0.074 l/l in the epicardial myocardium and remained at 0.341 +/- 0.082 l/l in the endocardial layer. These results indicate that tissue hematocrit gradient in the left ventricular myocardium may be disturbed if erythrocyte deformability is altered.