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Vol. 59, Issue 4, 825-836, April 2001
Department of Pharmacology, School of Medicine, Universidad
Complutense, Madrid, Spain
In the present study, we analyzed the effects of two angiotensin II
type 1 receptor antagonists, candesartan (0.1 µM) and eprosartan (1 µM), on hKv1.5, HERG, KvLQT1+minK, and Kv4.3 channels expressed on
Ltk
or Chinese hamster ovary cells using
the patch-clamp technique. Candesartan and eprosartan produced a
voltage-dependent block of hKv1.5 channels decreasing the current at
+60 mV by 20.9 ± 2.3% and 14.3 ± 1.5%, respectively. The
blockade was frequency-dependent, suggesting an open-channel
interaction. Eprosartan inhibited the tail amplitude of HERG currents
elicited on repolarization after pulses to +60 mV from 239 ± 78 to 179 ± 72 pA. Candesartan shifted the activation curve of HERG
channels in the hyperpolarizing direction, thus increasing the current
amplitude elicited by depolarizations to potentials between
50 and 0 mV. Candesartan reduced the KvLQT1+minK currents elicited by 2-s pulses
to +60 mV (38.7 ± 6.3%). In contrast, eprosartan transiently
increased (8.8 ± 2.7%) and thereafter reduced the KvLQT1+minK
current amplitude by 17.7 ± 3.0%. Eprosartan, but not
candesartan, blocked Kv4.3 channels in a voltage-dependent manner
(22.2 ± 3.5% at +50 mV) without modifying the voltage-dependence of Kv4.3 channel inactivation. Candesartan slightly prolonged the
action potential duration recorded in guinea pig papillary muscles at
all driving rates. Eprosartan prolonged the action potential duration
in muscles driven at 0.1 to 1 Hz, but it shortened this parameter at
faster rates (2-3 Hz). All these results demonstrated that candesartan
and eprosartan exert direct effects on Kv1.5, HERG, KvLQT1+minK, and
Kv4.3 currents involved in human cardiac repolarization.
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