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Characterization of large-conductance, calcium-activated potassium channels from human myometrium

, : Characterization of large-conductance, calcium-activated potassium channels from human myometrium. American Journal Of Obstetrics & Gynecology. 168(2): 652-660

Objectives: The purpose of our study was to detect and characterize potassium channels in the plasma membrane of smooth muscle cells from human myometrium. Study Design: Plasma membrane vesicles were incorporated into lipid bilayers to record single potassium channel activity. Results: We predominantly found a "maxi" calcium-activated potassium channel (261 picosiemens). This channel was calcium (micromoles per liter range) and voltage sensitive, highly selective for K+ over Na+ and Cs+, and was sensitive to external tetraethylammonium (dissociation constant apprxeq 220 mu-mol/L) and charybdotoxin (dissociation constant apprxeq 23 nmol/L). External apamin and 4-aminopyridine had no effect on this channel. Another type of potassium channel that was less frequently observed was also identified. It had a smaller conductance (142 picosiemens) and it seemed to be calcium independent (up to 50 nmol/L). Conclusion: Human myometrium possesses abundant "maxi" calcium-activated potassium channels. This channel shares common characteristics with other "maxi" calcium-activated potassium channels, including calcium and voltage gating, high conductance and selectivity, and channel pharmacologic profile.


PMID: 7679886

DOI: 10.1016/0002-9378(93)90513-I

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