Mechanical fragility of erythrocyte membrane in neonates and adults

Abstract

The shortened life span of neonatal red blood cells (RBC) is associated with accelerated membrane loss. The present study was designed to measure the critical shear force that causes membrane failure and the rate of membrane failure for neonatal and adult RBC. A micropi-pette technique was used to determine the membrane ex-tensional (shear) elastic modulus (i.e. resistance of the membrane to extensional elastic deformation), the rate of extensional membrane deformation (i.e. surface viscosity), and the tension for local membrane fragmentation. A flow channel system was used to determine the critical shear force of plastic membrane deformation (i.e. beginning of membrane tether formation), the rate of plastic deformation, and the plastic shear viscosity coefficient. The extensional elastic modulus of neonatal RBC was 18% smaller and the rate of elastic deformation was 25% longer compared with adult cells (p < 0.05). Membrane surface viscosity was similar for both cell types. The tension for local membrane fragmentation in the micropipette was 23% lower in neonates than in adults. However, the strain (i.e. extent of membrane deformation calculated as ratio of the stress resultant and the elastic modulus) at which membrane rupture in the micropipette occurred was similar for neonatal and adult RBC. This indicates that the smaller critical tension for neonatal RBC membrane failure was due to increased membrane elastic deformability. The critical shear force for membrane tether formation in the flow channel was similar for neonatal and adult RBC (1.17 ± 0.13 vs 1.19 ± 0.21 X 10-6 dyne, p > 0.1), whereas the tether growth was about two times faster and the plastic viscosity coefficient was 50% less for neonatal RBC compared with adult cells. These results indicate that the critical force for membrane failure is similar for neonatal and adult RBC if the increased membrane deformability of neonatal RBC is considered. However, once the membrane begins to fail, neonatal RBC appear to lose more membrane per unit time. © 1992 International Pediatric Research Foundation, Inc.