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1 Department of Physiology, Morehouse School of Medicine, Atlanta, Georgia 30310; and 2 Women's Health Initiative, State University of New York Health Science Center at Brooklyn, Brooklyn, New York 11203
Resting membrane potential (RMP) and whole cell currents were
recorded in human THP-1 monocytes adherent to polystyrene, unstimulated human umbilical vein endothelial cells (HUVECs),
lipopolysaccharide (LPS)-treated HUVECs, immobilized
E-selectin, or vascular cell adhesion molecule 1 (VCAM-1)
using the patch-clamp technique. RMP after 5 h on polystyrene was
24.3 ± 1.7 mV (n = 42) with delayed rectifier K+
(Idr) and
Cl
currents
(ICl) present
in >75% of the cells. Inwardly rectifying K+ currents
(Iir) were
present in only 14% of THP-1 cells. Adherence to unstimulated HUVECs
or E-selectin for 5 h had no effect on Iir or
ICl but decreased
Idr. Five hours
after adherence to LPS-treated HUVECs, outward currents were unchanged,
but Iir was
present in 81% of THP-1 cells. A twofold increase in
Iir and a
hyperpolarization (
41.3 ± 3.7 mV,
n = 16) were abolished by pretreatment
of THP-1 cells with cycloheximide, a protein synthesis inhibitor, or
herbimycin A, a tyrosine kinase inhibitor, or by pretreatment of the
LPS-treated HUVECs with anti-VCAM-1. Only a brief (15-min) interaction
between THP-1 cells and LPS-treated HUVECs was required to
induce Iir expression 5 h later. THP-1 cells adherent to VCAM-1 exhibited similar
conductances to cells adherent to LPS-treated HUVECs. Thus engagement
of specific integrins results in selective modulation of different
K+ conductances.
monocytic leukemia; integrin; adhesion molecules; ion channels; signaling
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