Chain length-dependent interaction of free fatty acids with the erythrocyte membrane.

Free fatty acids protect erythrocytes against hypotonic haemolysis in a certain low concentration range and become haemolytic at higher concentrations. The chain length dependence of this biphasic behaviour was investigated using human erythrocytes. The results can be summarized as follows: (i) A critical minimum chain length is required for both effects. Octanoic acid (C8) and fatty acids with a shorter chain length do not have any effect on the osmotic resistance of erythrocytes. (ii) Decanoic acid (C10) decreases the extent of hypo-osmotic haemolysis and does not become haemolytic at higher concentrations. (iii) Dodecanoic acid (C12) represents the minimum chain length for the typical concentration-dependent biphasic behaviour with protection against hypo-osmotic haemolysis at a certain low concentration range and subsequent haemolysis at higher concentrations. (iv) Tetradecanoic acid (C14) exhibits two concentration ranges of protection against hypo-osmotic haemolysis, each followed by haemolytic concentrations. (v) The observed effects are not correlated with the critical micellar concentrations of the investigated fatty acids.