title: Hypoxia increases BK channel activity in the inner mitochondrial membrane.
abstract: To explore the potential function of the BK channel in the inner mitochondrial membrane under physiological and hypoxic conditions, we used on-mitoplast and whole-mitoplast patches. Single BK channels had a conductance of 276+/-9 pS under symmetrical K(+) solutions, were Ca(2+)- and voltage-dependent and were inhibited by 0.1 microM charybdotoxin. In response to hypoxia, BK increased open probability, shifted its reversal potential (9.3+/-2.4 mV) in the positive direction and did not change its conductance. We conclude that (1) the properties at rest of this mitoplast K(+) channel are similar to those of BK channels in the plasma membrane; (2) hypoxia induces an increase, rather than a decrease (as in the plasmalemma), in the open probability of this K(+) channel, leading to K(+) efflux from the mitochondrial matrix to the outside. We speculate that this increase in K(+) efflux from mitochondria into the cytosol is important during hypoxia in maintaining cytosolic K(+).
authors.affiliation: Department of Pediatrics (Section of Respiratory Medicine), University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0735, USA.
authors.forename: Xiang Q
authors.initials: XQ
authors.lastname: Gu
authors.forename: Detlef
authors.initials: D
authors.lastname: Siemen
authors.forename: Suhel
authors.initials: S
authors.lastname: Parvez
authors.forename: Yu
authors.initials: Y
authors.lastname: Cheng
authors.forename: Jin
authors.initials: J
authors.lastname: Xue
authors.forename: Dan
authors.initials: D
authors.lastname: Zhou
authors.forename: Xiaolu
authors.initials: X
authors.lastname: Sun
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Jonas
authors.forename: Gabriel G
authors.initials: GG
authors.lastname: Haddad
mesh_terms: D002118:Calcium / Q000378:metabolism*; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D018999:Charybdotoxin / Q000494:pharmacology; D006801:Humans; D015640:Ion Channel Gating; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000502:physiology*; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000502:physiology*; D009498:Neurotoxins / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; D009498:Neurotoxins; D018999:Charybdotoxin; D011188:Potassium; D002118:Calcium