A hypertonicity-activated nonselective conductance in single proximal tubule cells isolated from mouse kidney

• Published in: The Journal of membrane biology Vol. 192; no. 3; pp. 191 - 201
• Main Authors: Balloch, K J D, Hartley, J A, Millar, I D, Kibble, J D, Robson, L
• Format: Journal Article
• Language: English
• Published: United States Springer Nature B.V 01-04-2003
• Subjects: Adenosine Triphosphate - pharmacology; Animals; Cell Size - physiology; Cells, Cultured; Cyclic AMP - metabolism; Electric Conductivity; Hypertonic Solutions; Ion Channel Gating - drug effects; Ion Channel Gating - physiology; Ion Channels - physiology; Kidney Tubules, Proximal - cytology; Kidney Tubules, Proximal - drug effects; Kidney Tubules, Proximal - physiology; Mechanotransduction, Cellular - physiology; Membrane Potentials - drug effects; Membrane Potentials - physiology; Mice; Mice, Inbred C57BL; Osmotic Pressure
• ISSN: 0022-2631; 1432-1424
• DOI: 10.1007/s00232-002-1075-8

The whole-cell patch-clamp technique was used to examine nonselective conductances in single proximal tubule cells isolated from mouse kidney. Single cells were isolated in either the presence or absence of a cocktail designed to stimulate cAMP. Patches were obtained with Na+ Ringer in the bath and Cs+ Ringer in the pipette. On initially achieving the whole-cell configuration, whole-cell currents were small. In cAMP-stimulated cells, with 5 mM ATP in the pipette solution, whole-cell currents increased with time. The activated current was linear, slightly cation-selective, did not discriminate between Na+ and K+ and was inhibited by 100 microM gadolinium. These properties are consistent with the activation of a nonselective conductance, designated G(NS). Activation of G(NS) was abolished with pipette AMP-PNP, ATP plus alkaline phosphatase or in the absence of ATP. In unstimulated cells G(NS) was activated by pipette ATP together with PKA. These data support the hypothesis that G(NS) is activated by a PKA-mediated phosphorylation event. G(NS) was also activated by a hypertonic shock. However, G(NS) does not appear to be involved in regulatory volume increase (RVI), as RVI was unaffected in the presence of the G(NS) blocker gadolinium. Instead, the ATP sensitivity of G(NS) suggests that it may be regulated by the metabolic state of the renal proximal tubule cell.