title: Hypertonicity activates nonselective cation channels in mouse cortical collecting duct cells.
abstract: We investigated the effect of cell shrinkage on whole-cell currents of M-1 mouse cortical collecting duct cells. Addition of 100 mM sucrose to an isotonic NaCl bath solution induced cell shrinkage and increased whole-cell currents within 5-10 min by approximately 12-fold. The effect was reversible upon return to isotonic solution and could also be elicited by adding 100 mM urea or 50 mM NaCl. Replacement of bath Na+ by K+, Cs+, Li+, or Rb+ did not significantly affect the stimulated inward current, but replacement by N-methyl-D-glucamine reduced it by 88.1 +/- 1.3% (n = 34); this demonstrates that hypertonicity activates a nonselective alkali cation conductance. The activation was independent of extra- and intracellular Ca2+, but 1 or 10 mM ATP in the pipette suppressed it in a concentration-dependent manner, indicating that intracellular ATP levels may modulate the degree of channel activation. Flufenamic acid (0.1 mM) and gadolinium (0.1 mM) inhibited the stimulated current by 68.7 +/- 5.9% (n = 9) and 32.4 +/- 11.7% (n = 6), respectively, whereas 0.1 mM amiloride had no significant effect. During the early phase of hypertonic stimulation single-channel transitions could be detected in whole-cell current recordings, and a gradual activation of 30 and more individual channels with a single-channel conductance of 26.7 +/- 0.4 pS (n = 29) could be resolved. Thus, we identified the nonselective cation channel underlying the shrinkage-induced whole-cell conductance that may play a role in volume regulation.
authors.affiliation: Zentrum der Physiologie, Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Volk
authors.forename: E
authors.initials: E
authors.lastname: Frömter
authors.forename: C
authors.initials: C
authors.lastname: Korbmacher
mesh_terms: D000227:Adenine Nucleotides / Q000378:metabolism; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002712:Chlorides / Q000378:metabolism; D005439:Flufenamic Acid / Q000494:pharmacology; D005682:Gadolinium / Q000494:pharmacology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D007685:Kidney Tubules, Collecting / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009994:Osmolar Concentration; D012965:Sodium Chloride / Q000494:pharmacology; D014508:Urea / Q000494:pharmacology
chemical_list: D000227:Adenine Nucleotides; D002712:Chlorides; D007473:Ion Channels; D012965:Sodium Chloride; D005439:Flufenamic Acid; D000584:Amiloride; D014508:Urea; D005682:Gadolinium; D002118:Calcium