Different expression of large-conductance calcium-activated K+ channels in human internal mammary and radial arteries.
OBJECTIVE
In this study, we investigated and compared the electrophysiological and molecular properties of large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels between human internal mammary arteries (IMA) and radial arteries (RA).


RESULTS
IMA and RA sections were obtained from 79 patients (including 9 females) undergoing coronary artery bypass graft surgery. We examined the effects of K(+) channel blockers tetraethylammonium (TEA), iberiotoxin (IBTX), and 4-aminopyridine (4-AP) on isolated smooth muscle cells (SMCs) using patch clamping. Both TEA (1 mM) and IBTX (0.1 µM) significantly decreased K(+) currents in IMA SMCs and RA SMCs, while 4-AP (1 mM) only had a weak effect. IBTX had a greater K(+)-blocking effect on IMA SMCs than on RA SMCs. Consistently, TEA and IBTX evoked significant constriction of both intact vascular rings. IBTX had a greater constrictor effect on IMA rings (18.5 ± 6.7%, n= 8) than on RA rings (10.6 ± 3.1%, n= 8), P< 0.05. RT-PCR and western blot analysis demonstrated that gene and protein expression of the α-subunit of BK(Ca) channels from IMA was greater than that from RA.


CONCLUSIONS
The density of BK(Ca) channels is greater in human IMA than in RA resulting in greater BK(Ca) currents in SMCs from IMA. This may partly explain the finding of less spasm in IMA grafts than in RA grafts. Our results may be of value in determining the best anti-spasm agent to use peri-operatively.
Shao
Yangzhen
Y
Research and Development Unit, National Heart Centre, Singapore. yangzhen.shao@wlab.gu.se
Liew
Reginald
R
Guan
Bingcai
B
Wong
Philip E H
PE
Shim
Winston S N
WS
Chua
Yeowleng
Y
He
Guowei
G
D015153:Blotting, Western; D001026:Coronary Artery Bypass / Q000009:adverse effects; D005260:Female; D006801:Humans; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000378:metabolism; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008323:Mammary Arteries / Q000187:drug effects / Q000378:metabolism* / Q000601:surgery; D008564:Membrane Potentials; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000601:surgery; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D017534:Radial Artery / Q000187:drug effects / Q000378:metabolism* / Q000601:surgery; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013035:Spasm / Q000209:etiology / Q000378:metabolism; D020858:Tissue and Organ Harvesting; D014661:Vasoconstriction
D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D026902:Potassium Channel Blockers