Inhibition of human erythrocyte and leukocyte Na+, K(+)-pump activity by lysophosphatidylcholines.

Synthetic lysophosphatidylcholines (LPCs) were examined for their effects on erythrocyte and leukocyte Na+,K(+)-pump activity, on erythrocyte Na+,K(+)-cotransport activity and on the passive permeability of the red blood cell membrane. Erythrocyte and leukocyte Na+,K(+)-pump activity was estimated by ouabain-sensitive 86Rb-uptake and erythrocyte Na+,K(+)-cotransport activity by bumetanide-sensitive 86Rb-uptake. Bumetanide, ouabain-resistant 86Rb-uptake was considered as a measure of the passive permeability of the red blood cell membrane. LPCs containing long chain fatty acids such as myristoyl, palmitoyl, lauroyl, stearoyl and oleoyl inhibited erythrocyte and leukocyte Na+,K(+)-pump activity and erythrocyte Na+,K(+)-cotransport activity, while they stimulated the passive membrane permeability of the red blood cells. LPCs containing lauroyl, the shortest fatty acid in this group, had the lowest inhibitory activity, while LPCs with intermediate chain length fatty acids such as caproyl and decanoyl had no effect. The order of inhibitory action of these LPCs on erythrocyte and leukocyte Na+,K(+)-pump activity was: palmitoyl greater than stearoyl greater than myristoyl greater than oleoyl greater than lauroyl.