Aging of the erythrocyte. IX. Fluorescence studies on changes in membrane properties.

Fluorescence studies of membranes prepared from density-separated red blood cells demonstrated an increase in lipid viscosity (judging from fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene and 1-aminonaphthalene-8-sulfonate and changes in the physical state of proteins (judging from tryptophan fluorescence intensity and polarization). These alterations may be partly due to lipid peroxidation. In vivo accumulation of products of this process in the membranes was confirmed. Changes were also found in the distribution pattern of cell populations of different mean age in a cell sorter, probably due to alterations in rheological properties of the erythrocytes.