Nitric oxide stimulates a large-conductance Ca-activated K+ channel in human skin fibroblasts through protein kinase G pathway.
In order to investigate the large-conductance Ca(2+)-activated K(+) (BK(Ca)) channel and determine the effects of nitric oxide (NO) on the channel in human skin fibroblasts, we performed electrophysiological patch clamp recordings on 5th-passage cells of human genital skin cultures. The whole-cell outward K(+) current was increased with depolarization, and proved to be sensitive to NS1619 (a selective BK(Ca) channel activator) and iberiotoxin (a specific BK(Ca )channel inhibitor). The single-channel currents showed 226 pS of mean conductance in symmetrical K(+). Sodium nitroprusside (SNP; an NO donor) significantly increased the K(+) current amplitude in the whole-cell mode, and open probability of the channel (NPo) in the cell-attached mode, but not in the inside-out mode. S-nitroso-N-acetylpenicillamine (an NO donor) and 8-Br-cGMP (a membrane-permeant cGMP analogue) also increased the BK(Ca )channel activity. The stimulatory effect of SNP on BK(Ca) channels was inhibited by pretreatment with 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one (a soluble guanylyl cyclase inhibitor), or KT5823 [a specific protein kinase G (PKG) inhibitor]. Cytoplasmic PKG also increased the channel activity in inside-out patches. In conclusion, the present data indicate that BK(Ca) channels constitute a significant fraction of K(+) current in human skin fibroblasts, and that NO increases NPo of BK(Ca) channels, which are mediated via the cGMP/PKG pathway, without direct effects on the channel.
Lim
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I
Department of Physiology, College of Medicine, Chung-Ang University, Seoul, Korea. injalim@cau.ac.kr
Yun
J
J
Kim
S
S
Lee
C
C
Seo
S
S
Kim
T
T
Bang
H
H
D001562:Benzimidazoles / Q000494:pharmacology; D002227:Carbazoles / Q000494:pharmacology; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D015640:Ion Channel Gating; D008564:Membrane Potentials / Q000187:drug effects; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism*; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D012867:Skin / Q000166:cytology
D001562:Benzimidazoles; D002227:Carbazoles; D007211:Indoles; D020030:Nitric Oxide Donors; D010455:Peptides; D024681:Potassium Channels, Calcium-Activated; C073601:KT 5823; C086491:NS 1619; D009599:Nitroprusside; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; C064719:iberiotoxin; D026423:S-Nitroso-N-Acetylpenicillamine; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP; D011188:Potassium