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1 Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157; and 2 Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta, Georgia 30912
We assessed the effect of epoxyeicosatrienoic acids
(EETs) in intact mesenteric arteries and Ca2+-activated
K+ (BKCa) channels of isolated vascular
smooth muscle cells from control and insulin-resistant (IR) rats. The
response to 11,12-EET and 14,15-EET was assessed in small mesenteric
arteries from control and IR rats in vitro. Mechanistic studies were
performed in endothelium intact or denuded arteries and in the presence
of pharmacological inhibitors. Moreover, EET-induced activation of the
BKCa channel was assessed in myocytes in both the
cell-attached and the inside-out (I/O) patch-clamp configurations. In
control arteries, both EET isomers induced relaxation. Relaxation was
impaired by endothelium denudation,
N
-nitro-L-arginine, or
iberiotoxin (IBTX), whereas it was abolished by IBTX + apamin or
charybdotoxin + apamin. In contrast, the EETs did not
relax IR arteries. In control myocytes, the EETs increased BKCa activity in both configurations. Conversely, in
the cell-attached mode, EETs had no effect on BKCa
channel activity in IR myocytes, whereas in the I/O configuration,
BKCa channel activity was enhanced. EETs induce
relaxation in small mesenteric arteries from control rats through
KCa channels. In contrast, arteries from IR rats do
not relax to the EETs. Patch-clamp studies suggest impaired relaxation
is due to altered regulatory mechanisms of the BKCa channel.
calcium-dependent K+ channels; vascular smooth muscle; endothelium
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