Different mechanisms underlying the stimulation of K(Ca) channels by nitric oxide and carbon monoxide.
The molecular mechanisms underlying the effects of nitric oxide (NO) and carbon monoxide (CO), individually and collectively, on large-conductance calcium-activated K(+) (K(Ca)) channels were investigated in rat vascular smooth muscle cells (SMCs). Both NO and CO increased the activity of native K(Ca) channels. Dehydrosoyasaponin-I, a specific agonist for beta subunit of K(Ca) channels, increased the open probability of native K(Ca) channels only when it was delivered to the cytoplasmic surface of membrane. CO, but not NO, further increased the activity of native K(Ca) channels that had been maximally stimulated by dehydrosoyasaponin-I. After treatment of SMCs with anti-K(Ca),beta subunit antisense oligodeoxynucleotides, the stimulatory effect of NO, but not of CO, on K(Ca) channels was nullified. CO, but not NO, enhanced the K(Ca) current densities of heterologously expressed cloned K(Ca),alpha subunit, showing that the presence of K(Ca),beta subunit is not a necessity for the effect of CO but essential for that of NO. Finally, pretreatment of SMCs with NO abolished the effects of subsequently applied CO or diethyl pyrocarbonate on K(Ca) channels. In summary, the stimulatory effects of CO and NO on K(Ca) channels rely on the specific interactions of these gases with K(Ca),alpha and K(Ca),beta subunits.
Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Lingyun
L
Wu
Kun
K
Cao
Yanjie
Y
Lu
Rui
R
Wang
D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D002248:Carbon Monoxide / Q000494:pharmacology*; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008297:Male; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D009828:Oleanolic Acid / Q000031:analogs & derivatives*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D024681:Potassium Channels, Calcium-Activated / Q000819:agonists / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D012503:Saponins / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D014315:Triterpenes / Q000494:pharmacology
D020030:Nitric Oxide Donors; D016376:Oligonucleotides, Antisense; D024681:Potassium Channels, Calcium-Activated; D012503:Saponins; D014315:Triterpenes; C071764:dehydrosoyasaponin I; D009599:Nitroprusside; D009569:Nitric Oxide; D009828:Oleanolic Acid; D002248:Carbon Monoxide; D011188:Potassium; D002118:Calcium