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Vol. 294, Issue 3, 955-962, September 2000
Departments of Pharmacology and Medicine, Vanderbilt University
School of Medicine, Nashville, Tennessee (I.C.-H.Y., P.B.B., K.T.M.);
and Cardiovascular Research Department, Procter & Gamble
Pharmaceuticals, Mason, Ohio (M.W.S., A.B.)
Selective inhibitors of the slow component of the cardiac delayed
rectifier K+ current, IKs, are of interest as
novel class III antiarrhythmic agents and as tools for studying the
physiologic roles of the IKs current. Racemic chromanol
293B is an inhibitor of both native IKs and its putative
molecular counterpart, the KvLQT1+minK ion channel complex. We
synthesized the (+)-[3S,4R] and
(
)-[3R,4S] enantiomers of chromanol
293B using chiral intermediates of known absolute configuration and
determined their relative potency to block recombinant human
K+ channels that form the basis for the major repolarizing
K+ currents in human heart, including KvLQT1+minK, human
ether-a-go-go-related gene product (hERG), Kv1.5, and Kv4.3,
corresponding to the slow (IKs), rapid (IKr),
and ultrarapid (IKur) delayed rectifier currents and the
transient outward current (ITo), respectively.
K+ channels were expressed in mammalian cells and currents
were recorded using the whole-cell patch-clamp technique. We found that
the physicochemical properties and relative potency of the enantiomers
differed from those reported previously, with
(
)-[3R,4S]293B nearly 7-fold more
potent in block of KvLQT1+minK than
(+)-[3S,4R]293B, indicating that the
original stereochemical assignments were reversed. K+
current inhibition by (
)-293B was selective for KvLQT1+minK over
hERG, whereas the stereospecificity of block for KvLQT1+minK and Kv1.5
was preserved, with (
)-293B more potent than (+)-293B for both
channel complexes. We conclude that the
(
)-[3R,4S] enantiomer of chromanol
293B is a selective inhibitor of KvLQT1+minK and therefore a useful
tool for studying IKs.
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