THE EFFECTS OF PALMITATE ON HUMAN ERYTHROCYTE-MEMBRANE POTENTIAL AND OSMOTIC STABILITY

To evaluate the mechanism(s) of erythrocyte stabilization in hypotonic medium by free fatty acids, we have studied the effect of palmitic ac id and its derivatives on human erythrocyte membrane electrochemical p roperties, osmotic stability and fluidity. Palmitic acid increased the membrane potential to the highest extent as compared with its derivat ives. The membrane potential was equal to -11.0 +/- 1.7 mV in the abse nce and -23.3 +/- 3.2 mV in the presence of 400 mu mol l(-1) of palmit ic acid, -15.3 +/- 2.2 mV in the presence of 400 mu mol l(-1) of methy l ester of palmitic acid and -14.2 +/- 1.8 mV in the presence of 400 m u Mol l(-1) of lauric aldehyde. We propose that free fatty acids, cont aining the charged carboxylic end group, in contrast to the correspond ing esters or aldehydes, can act as ionophores. At the same time, the osmotic stabilization of erythrocytes by palmitic acid and its derivat ives was higher in sodium-containing as compared with potassium-contai ning media and did not correlate with the effect of these compounds on the membrane potential. We suggest that protective potassium leakage does not play a main role in erythrocyte osmotic stabilization by free fatty acids. Possibly this stabilization is due to the structural rea rrangement of the whole membrane.