title: pH modulation of large conductance potassium channel from adrenal chromaffin granules.
abstract: We report here that large conductance K(+) selective channel in adrenal chromaffin granules is controlled by pH. We measured electrogenic influx of (86)Rb(+) into chromaffin granules prepared from bovine adrenal gland medulla. The (86)Rb(+) influx was inhibited by acidic pH. Purified chromaffin granule membranes were also fused with planar lipid bilayer. A potassium channel with conductance of 432+/-9 pS in symmetric 450 mM KCl was observed after reconstitution into lipid bilayer. The channel activity was unaffected by charybdotoxin, a blocker of the Ca(2+)-activated K(+) channel of large conductance. It was observed that acidification to pH 6.4 cis side of the membrane lowered the channel open probability and single channel conductance. Whereas only weak influence on the single channel current amplitude and open probability were observed upon lowering of the pH at the trans side. We conclude that a pH-sensitive large conductance potassium channel operates in the chromaffin granule membrane.
authors.affiliation: Department of Biophysics, Agriculture University, Warsaw, Poland.
authors.forename: Renata
authors.initials: R
authors.lastname: Hordejuk
authors.forename: Nikolai A
authors.initials: NA
authors.lastname: Lobanov
authors.forename: Anna
authors.initials: A
authors.lastname: Kicinska
authors.forename: Adam
authors.initials: A
authors.lastname: Szewczyk
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Dolowy
mesh_terms: D000313:Adrenal Medulla / Q000166:cytology / Q000502:physiology*; D000818:Animals; D002417:Cattle; D002837:Chromaffin Granules / Q000737:chemistry / Q000502:physiology*; D004553:Electric Conductivity; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport / Q000502:physiology; D008051:Lipid Bilayers / Q000737:chemistry; D008564:Membrane Potentials / Q000502:physiology; D015221:Potassium Channels / Q000502:physiology*; D012414:Rubidium Radioisotopes / Q000032:analysis / Q000378:metabolism
chemical_list: D008051:Lipid Bilayers; D015221:Potassium Channels; D012414:Rubidium Radioisotopes