pH effects on high conductance Ca2+-activated K+ channels (BK(Ca)) in human internal mammary artery smooth muscle cells.
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.
Raingo
Jesica
J
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.
Rebolledo
Alejandro
A
Grassi de Gende
Angela O
AO
Sanz
Nora
N
Tommasi
Juan
J
Milesi
Verónica
V
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*
D051036:Large-Conductance Calcium-Activated Potassium Channels; D010455:Peptides; D024681:Potassium Channels, Calcium-Activated; C064719:iberiotoxin