The Effect of Tienilic Acid on Na+ and K+ Transport in Human Red Cells

DANIELE CUSI; RICARDO GARAY

Abstract

Tienilic acid inhibits erythrocyte Na⁺,K⁺ cotransport to a lesser extent than does furosemide. This property seems to be proportional to its diuretic effects. Under conditions in which the erythrocytes have all of their saturable Na⁺ and K⁺ transport systems blocked, the addition of tienilic acid induces an increase in K⁺ permeability. This effect shows saturation kinetics with the increase in the internal K⁺ concentration and could not be inhibited by ethylene glycol bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid quinine, carbocyanine, or tetraethylammonium. These results suggest that the main effects of tienilic acid on transmembrane cation transport may be the opening of transient or permanent K⁺ channels.

ACKNOWLEDGMENTS We are indebted to V. Lew (Cambridge University, Cambridge, England), P. Lauf (Duke University, Durham, N. C.), P. Ascher and H. M. Gerschenfeld (Ecole Normale Supérieure, Paris), and P. Meyer (Hôpital Necker, Paris) for interest and discussion. We are also indebted to M. Saunders and J. G. Mongeot who helped with the writing of the manuscript. We wish to thank Anphar for the provision of tienilic acid, MSD for the gift of amioride, Prophac for spironolactone, Ciba-Geigy for hydrochlorathiazide, Hoechst for furosemide, and Lab. Servier for indapamide.