EFFECT OF FREE FATTY-ACIDS ON ERYTHROCYTE MORPHOLOGY AND MEMBRANE FLUIDITY

Changes in red blood cell shape and membrane properties in response to the interaction with free fatty acids and their derivatives were stud ied by light scattering at small and large angles, light microscopy an d fluorescence anisotropy. The influence of these agents depended on t he end groups and increased with increasing chain length. The fatty ac ids exerted a biphasic effect on the cell size, shape and surface prop erties, and induced erythrocyte aggregation. After transient size alte ration with a reduction in diameter, caused by low free fatty acid con centrations (up to 5-10 mu M in the case of palmitic acid), fatty acid s increased the erythrocyte diameter at higher concentrations (20-60 m u M in the case of palmitic acid). The aliphatic aldehydes and methyl esters of fatty acids significantly decreased the cell diameter at the concentrations used. Changes in erythrocyte shape and size were accom panied by changes in membrane microviscosity. Palmitic acid decreased the rotational diffusion of the fluorescence probe incorporated into t he membrane whereas methyl ester of palmitic acid and lauric aldehyde increased probe mobility. Also the erythrocyte modification by malondi aldehyde influenced cell morphology and highly decreased membrane flui dity.