Fusion of cultured dog kidney (MDCK) cells: II. Relationship between cell pH and K conductance in response to aldosterone.

Autor: Oberleithner, Hans, Kersting, Ulrich, Silbernagl, Stefan, Steigner, Wieland, Vogel, Ulrich
Zdroj: Journal of Membrane Biology; 1989, Vol. 111 Issue 1, p49-56, 8p
Abstrakt: We have chosen the MDCK cell line to investigate aldosterone action on H transport and its role in regulating cell membrane K conductance ( G). Cells grown in a monolayer respond to aldosterone indicated by the dose-dependent formation of domes and by the alkalinization of the dome fluid. The pH sensitivity of the plasma membrane K channels was tested in 'giant cells' fused from individual MDCK cells. Cytoplasmic pH (pH) and G were measured simultaneously while the cell interior was acidified gradually by an extracellular acid load. We found a steep signoidal relationship between pH and G (Hill coefficient 4.4±0.4), indicating multiple H binding sites at a single K channel. Application of aldosterone increased pH within 120 min from 7.22±0.04 to 7.45±0.02 and from 7.15±0.03 to 7.28±0.02 in the absence and presence of the CO/HCO buffer system, respectively. We conclude that the hormone-induced cytoplasmic alkalinization in the presence of CO/ HCO is limited by the increased activity of a pH-regulating HCO extrusion system. Since G is stimulated half-maximally at the pH of 7.18±0.04, internal H ions could serve as an effective intracellular signal for the regulation of transepithelial K flux. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
Externí odkaz: