The effect of cyclic nucleotides and icosanoids on Na+ and K+ transport in human red cells.

Cyclic AMP inhibits the bumetanide-sensitive Na+,K+ cotransport system in human red cells. The cotransport inhibition is enhanced by addition of phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine to the incubation medium. The cyclic AMP concentration giving half-maximal cotransport inhibition showed a wide variation among different individuals (from 0.1 to 5 mM external cyclic AMP concentration). In contrast to cyclic AMP, cyclic GMP showed little effect on the cotransport system. The ouabain-sensitive Na+,K+ pump was almost unaffected by cyclic nucleotides. Prostacyclin was the only tested prostaglandin showing an effect on Na+ and K+ transport in human red cells. In some individuals, this icosanoid stimulated the Na+,K+ cotransport system. Leukotriene B4 stimulated K+ fluxes.