Endothelium-independent effect of estrogen on Ca(2+)-activated K(+) channels in human coronary artery smooth muscle cells.
OBJECTIVE
Postmenopausal estrogen replacement therapy lowers the incidence of cardiovascular disease, suggesting that estrogens support cardiovascular function. Estrogens dilate coronary arteries; however, little is known about the molecular basis of how estrogen affects the human coronary circulation. The cellular/molecular effects of estrogen action on human coronary smooth muscle were investigated in the present study.


METHODS
Patch-clamp and fluorescent microscopy studies were performed on human coronary myocytes in the absence of endothelium.


RESULTS
Estrogen increased whole-cell currents over a range of membrane potentials, and further studies indicated that the large-conductance (186.5 +/- 3 pS), calcium- and voltage-activated potassium (BK(Ca)) channel was the target of estrogen action. Channel activity was stimulated approximately 15-fold by nanomolar concentrations of 17 beta-estradiol, and this stimulation was reversed >90% by inhibiting cGMP-dependent protein kinase activity with 300 nM KT5823. 17 beta-Estradiol increased the level of cGMP and nitric oxide in human myocytes, and the stimulatory effect of estrogen on channel activity and NO production was reversed by inhibiting NO synthase with 10 microM N(G)-monomethyl-L-arginine.


CONCLUSIONS
Our cellular and molecular studies identify the BK(Ca) channel as a target of estrogen action in human coronary artery smooth muscle. This response to estrogen involves cGMP-dependent phosphorylation of the BK(Ca) channel or a closely associated regulatory molecule, and further evidence suggests involvement of the NO/cGMP signaling system in coronary smooth muscle. These findings are the first to provide direct evidence for a molecular mechanism that can account for endothelium-independent effects of estrogen on human arteries, and may also help explain why estrogens reduce myocardial ischemia and stimulate coronary blood flow in patients with diseased coronary arteries.
White
Richard E
RE
Department of Pharmacology and Toxicology, Medical College of Georgia, 1120 15th Street, Augusta, GA 30912-2300, USA. rwhite@mail.mcg.edu
Han
Guichun
G
Maunz
Melissa
M
Dimitropoulou
Christiana
C
El-Mowafy
Abdalla M
AM
Barlow
Robert S
RS
Catravas
John D
JD
Snead
Connie
C
Carrier
Gerald O
GO
Zhu
Shu
S
Yu
Xiuping
X
D000470:Alkaloids / Q000494:pharmacology; D000704:Analysis of Variance; D002227:Carbazoles; D003331:Coronary Vessels; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology*; D006801:Humans; D007211:Indoles; D008856:Microscopy, Fluorescence; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology*; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects*; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects*; D019323:omega-N-Methylarginine / Q000494:pharmacology
D000470:Alkaloids; D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D010455:Peptides; D024681:Potassium Channels, Calcium-Activated; D024642:Potassium Channels, Voltage-Gated; C073601:KT 5823; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D004958:Estradiol; C064719:iberiotoxin; D000242:Cyclic AMP; D019001:Nitric Oxide Synthase; D017868:Cyclic AMP-Dependent Protein Kinases