EFFECT OF pH AND OSMOLALITY ON THE DEFORMABILITY OF DENSITY SEPARATED RED BLOOD CELLS

Abstract

1.5 p1 of unfractionated and density-separated red blood cells (RBC) of healthy adult donors were suspended in Dextran-70 buffer solutions (32cP) at different pH-values (range: 6.9 to 8.0) and osmolalities (range: 200 to 600 mmollkg). The RBC elongations were measured by a Rheoscope at different shear stresses and evaluated semiautomatically. Results: 1. Acidosis did not impair RBC deformability in any of the fractions. 2. Alcalosis caused a slight decrease in the deformability of non-fractioned RBC, whereas the deformability of aged RBC fell markedly. The young RBC remained uneffected. 3. Hyposmolality moderately increased the deformability of young cells. This increase in deformability was more pronounced for non-fractionated and aged RBC. 4. Hyperosmolality significantly reduced RBC deformability, especial19 in the non-fractionated and aged RBC population. We conclude that young RBC withstand severe alcalosis or hyper-osmolality better than aged RBC. Red blood c e l l (RBC) aggregation induced by f i b r i n o g e n i s a major determinant o f t h e non-Newtonian f l o w behavior o f blood and has been suggested as a p o s s i b l e c o n t r i b u t i n g f a c t o r f o r disturbed microcircu-l a t o r y f l o w and thrombogenesis. The purpose o f the present i n v e s t i g at i o n was t o evaluate several experimental measures o f RBC aggregation i n order t o determine t h e i r a b i l i t y t o d i f f e r e n t i a t e between groups w i t h low (25 neonates), normal (35 a d u l t c o n t r o l s) , and h i g h (59 pregnant women, 24 n e p h r o t i c syndrome) f i b r i n o g e n l e v e l s. The f o l l o w-i n g aggregation measures were employed: 1) Microscopic Aggregation Index (MAI); 2) Zeta Sedimentation R a t i o (ZSR); 3) Aggregation H a l f Time (AHT) a f t e r cessation o f shear; 4) R e l a t i v e L i g h t Transmission (RLT) a f t e r 1 and l o minutes o f s t a s i s ; 5) shear r a t e a t Minimum L i g h t Transmission (MLT) ; 5) Myrenne Erythrocyte Aggregation(MEA) .