K+ and Ca2+ channel activity and cytosolic [Ca2+] in oxygen-sensing tissues.
Ion channels are known to participate in the secretory or mechanical responses of chemoreceptor cells to changes in oxygen tension (P(O2)). We review here the modifications of K+ and Ca2+ channel activity and the resulting changes in cytosolic [Ca2+] induced by low P(O2) in glomus cells and arterial smooth muscle which are well known examples of O2-sensitive cells. Glomus cells of the carotid body behave as presynaptic-like elements where hypoxia produces a reduction of K+ conductance leading to enhanced membrane excitability, Ca2+ entry and release of dopamine and other neurotransmitters. In arterial myocytes, hypoxia can inhibit or potentiate Ca2+ channel activity, thus regulating cytosolic [Ca2+] and contraction. Ca2+ channel inhibition is observed in systemic myocytes and most conduit pulmonary myocytes, whereas potentiation is seen in a population of resistance pulmonary myocytes. The mechanism whereby O2 modulates ion channel activity could depend on either the direct allosteric modulation by O2-sensing molecules or redox modification by reactive chemical species.
López-Barneo
J
J
Departamento de Fisiología Médica y Biofisica, Universidad de Sevilla, Facultad de Medicina, Spain. lbarneo@cica.es
Pardal
R
R
Montoro
R J
RJ
Smani
T
T
García-Hirschfeld
J
J
Ureña
J
J
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D002344:Carotid Body / Q000166:cytology / Q000378:metabolism; D015687:Cell Hypoxia / Q000502:physiology; D002628:Chemoreceptor Cells / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*
D015220:Calcium Channels; D015221:Potassium Channels; D010100:Oxygen; D002118:Calcium