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High Activity of Large‐conductance Ca 2+ ‐activated K + channels Underlies Weak Myogenic Tone of Rat Mesenteric Arteries in Comparison of Cerebral Artery
Author(s) -
Seo Eun Yeong,
Yun Myung Churl,
Zhang Yin Hua,
Kim Sung Joon
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.804.1
Subject(s) - iberiotoxin , mechanosensitive channels , chemistry , vasoconstriction , depolarization , mesenteric arteries , myogenic contraction , cerebral arteries , medicine , artery , patch clamp , bk channel , vasodilation , biophysics , anatomy , potassium channel , endocrinology , cardiology , electrophysiology , ion channel , biology , smooth muscle , receptor
Myogenic tone (MT) of resistance artery, vasoconstriction in response to increasing luminal pressure (P lum ), stabilizes regional blood flow albeit the fluctuation of perfusion pressure. The levels of MT differ between vascular beds. Mechanosensitive depolarization of membrane potential and activation of voltage‐gated Ca 2+ channels (VOCCs) are cellular mechanisms for MT in smooth muscle cells (SMCs). Large‐conductance Ca 2+ ‐activated K + channel (BK Ca ) in SMCs may antagonize the contractile signals in MT. Using video‐analysis of pressurized (60 mmHg) artery, we found that MT in mesenteric artery (MA) is significantly smaller than that of cerebral artery (CA). Iberiotoxin, a selective BK Ca inhibitor, augmented the MT of MA by larger extent than CA. Patch clamp analysis showed that not only the BK Ca current density but also unitary slope conductance of MASMC are higher than CASMCs. In addition, the frequency of spontaneous transient outward currents (STOCs) reflecting the BK Ca activity in responses to Ca 2+ sparks was higher in MASMCs. Voltage‐gated K + channel (Kv) activity was also higher in MASMCs. Although Ba 2+ ‐sensitive inwardly rectifying K + current is larger in CASMCs, pretreatment with Ba 2+ did not induce significant augmentation of iberiotoxin sensitivity of MT in CA. Taken together, it is suggested that more frequent STOCs and larger average outward current via BK Ca could explain the weak MT in MA.