Cation permeability and mechanical properties of the erythrocyte membrane under the influence of lysophosphatidylcholine (LPC) in isotonic and hypotonic media

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Abstract
The osmotic behavior of erythrocytes under the influence of lysophosphatidylcholine (LPC) was investigated at temperatures of +4.degree. C and 20.degree. C by allowing them to swell rapidly in hypotonic media in the presence of LPC or to swell gradually at first and then interact with LPC. Prelytic K release, the degree of hemolysis and the cell volume under various osmotic conditions were measured, together with the returning volumes, i.e., the volumes in an isotonic solution to which the cells returned from that in the hypotonic solution. LPC had a hemolyzing effect on erythrocytes in an isotonic medium and in slightly hypotonic media under all the osmotic conditions investigated. The degree of hemolysis increased with increasing concentrations of LPC or decreasing temperatures, being greater during gradual than during rapid swelling. LPC also produced a prelytic leakage of K connected with the decrease in cell volume in an isotonic medium and in returning volumes in all the media and under all the osmotic conditions investigated. The semipermeability of the membrane was preserved in all these cases; however, erythrocyte osmotic swelling was observed, although to a lesser extent than without LPC. During rapid swelling both the curves for the prelytic K leakage and the degree of hemolysis were shifted towards more dilute solutions. Since the critical hemolytic volume was not increased, the shift in K leakage and hemolysis caused by LPC may be due to increased rigidity in the cell membrane. The curves for both K leakage and hemolysis shifted towards more concentrated solutions during gradual swelling, perhaps due to increased membrane fragmentation.