title: pH effects on high conductance Ca2+-activated K+ channels (BK(Ca)) in human internal mammary artery smooth muscle cells.
abstract: BACKGROUND
  In vascular smooth muscle cells, different types of K+ channels participate in the regulation of membrane potential and consequently in the contractile behavior of the vessel. There is little information about the properties and role of K+ channels in human internal mammary artery (HIMA), the vessel of choice for coronary revascularization.
  
  
  METHODS
  Patch-clamp technique on isolated HIMA smooth muscle cells was used.
  
  
  RESULTS
  This work presents for the first time single-channel properties of the high conductance Ca2+-activated K+ channel (BK(Ca)) of HIMA. It presents a single-channel conductance of 228+/-4 pS (n=44, 8 cells), is sensitive to 100 nM iberiotoxin, and its open probability is Ca2+- and voltage-dependent. Inside-out results show that BK(Ca) channels in HIMA are directly activated by increasing the pH of intracellular media (NPo=0.096+/-0.032 at pH 7.4 and NPo=0.459+/-0.111 at pH 7.6, n=12 cells, p<0.05) and inhibited by lowering this pH (NPo=0.175+/-0.067 at pH 7.4 and NPo=0.051+/-0.019 at pH 6.8, n=13 cells, p<0.05).
  
  
  CONCLUSIONS
  The evidences presented about single-channel properties and intracellular pH sensitivity of BK(Ca) from HIMA smooth muscle cells provide useful information to elucidate physiological or pathological mechanisms in this vessel, as well as for future studies where drugs could have BK(Ca) channels as targets for pharmacological therapies.
authors.affiliation: Cátedra de Fisiología, Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), Calles 47 y 115, La Plata (1900), Argentina.
authors.forename: Jesica
authors.initials: J
authors.lastname: Raingo
authors.forename: Alejandro
authors.initials: A
authors.lastname: Rebolledo
authors.forename: Angela O
authors.initials: AO
authors.lastname: Grassi de Gende
authors.forename: Nora
authors.initials: N
authors.lastname: Sanz
authors.forename: Juan
authors.initials: J
authors.lastname: Tommasi
authors.forename: Verónica
authors.initials: V
authors.lastname: Milesi
mesh_terms: D000704:Analysis of Variance; D004594:Electrophysiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008323:Mammary Arteries / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology*; D009130:Muscle, Smooth / Q000378:metabolism / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010455:Peptides; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism*
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; D010455:Peptides; D024681:Potassium Channels, Calcium-Activated; C064719:iberiotoxin