Occurrence of passive furosemide-sensitive transmembrane potassium transport in cultured cells

• Published in: Biochimica et biophysica acta Vol. 646; no. 3; p. 389
• Main Authors: Aiton, J F, Chipperfield, A R, Lamb, J F, Ogden, P, Simmons, N L
• Format: Journal Article
• Language: English
• Published: Netherlands 07-09-1981
• Subjects: Animals; Anions - pharmacology; Biological Transport - drug effects; Cells, Cultured; Chick Embryo; Chlorides - pharmacology; Furosemide - pharmacology; Humans; Myocardium - metabolism; Ouabain - pharmacology; Potassium - metabolism; Sodium - pharmacology
• ISSN: 0006-3002
• DOI: 10.1016/0005-2736(81)90307-2

Furosemide (1 x 10(-4) M) inhibits a proportion of the total passive (ouabain-insensitive) K+ influx into primary chick heart cell cultures (85%), BC3H1 cells (75%), MDCK cells (40%) and HeLa cells (57%). This action of furosemide upon K+ influx is independent of (Na+ + K+)-pump inhibition since the furosemide-sensitive component of the K+ influx is identical in the presence and absence of ouabain (1 x 10(-3) M). For HeLa cells the passive, furosemide-sensitive component of K+ influx is markedly dependent upon the external K+, Na+ and Cl- content. Acetate, iodide and nitrate are ineffective as substitutes for Cl-, whereas Br- is partially effective. Partial Cl- replacement by NO3- gave an apparent affinity of 100 mM [Cl]. Na+ replacement by choline+ abolishes the furosemide-sensitive component, whereas Li+ replacement reduces this component by 48%. Partial Na+ replacement by choline+ gives an apparent affinity of 25 mM [Na+]. Variation in the external K+ content gives an affinity for the furosemide-sensitive component of approx. 1.0 mM. Furosemide inhibition of the passive K+ influx is of high affinity, half-maximal inhibition being observed at 5 x 10(-6) M furosemide. Piretanide (1 x 10(-4) M) and phloretin (1 x 10(-4) M) inhibit the same component of passive K+ influx as furosemide; ethacrynic acid and amiloride (both 1 x 10(-4) M) partially so. The stilbene, SITS (1 x 10(-6) M), was ineffective as an inhibitor for the furosemide-sensitive component.