Non-esterified long-chain
fatty acids reduce the extent of hypotonic
hemolysis at a certain low concentration range but cause
hemolysis at higher concentrations. This biphasic behavior was investigated at different temperatures (0-37 degrees C) for lauric (12:0), myristic (14:0), palmitoleic (16:1), oleic (cis-18:1) and elaidic (trans-18:1)
acids. The results are summarized as follows: (A) the
fatty acids examined exhibit a high degree of specificity in their thermotropic behavior; (B)
oleic acid protects against hypotonic
hemolysis even at the highest concentrations, up to 15 degrees C, when it becomes hemolytic, but only in a limited concentration range; (C)
elaidic acid does not affect the osmotic stability of erythrocytes up to 20 degrees C, when it starts protecting: above 30 degrees C, it becomes hemolytic at the highest concentrations; (D)
palmitoleic acid is an excellent protecting agent at all temperatures in a certain concentration range, becoming hemolytic at higher concentrations; (E)
lauric acid protects up to 30 degrees C and becomes hemolytic only above this temperature; (F)
myristic acid exhibits an extremely unusual behavior at 30 and 37 degrees C by having alternating concentration ranges of protecting and hemolytic effects; (G) there is a common critical temperature for
hemolysis at 30 degrees C for saturated and trans-
unsaturated fatty acids; (H) the initial slope of Arrhenius plots of percent
hemolysis at the concentration of maximum protection is negative for cis-
unsaturated fatty acids and positive for saturated and trans-
unsaturated fatty acids.