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Department of Physiology, University of South Alabama, Mobile, Alabama 36688
We have previously shown that ANG II increases
microvascular permeability in normal dog lungs but not after
pacing-induced heart failure. This study investigated how ANG II
induces permeability in isolated blood-perfused canine lung lobes and
what alterations occur during heart failure. In normal lobes, the
protein kinase C (PKC) inhibitors staurosporine (500 nM) or
chelerythrine (10 µM) did not modify ANG II-induced increases in the
capillary filtration coefficient
(Kf,c,
ml · min
1 · cmH2O
1 · 100 g
1; an index of
microvascular permeability), suggesting that PKC is not involved.
Thapsigargin (150 nM) was used to stimulate capacitative Ca2+ entry in lobes from control
dogs and dogs paced at 245 beats/min for 4 wk to induce heart failure.
In control lobes,
Kf,c rose after
thapsigargin, from 0.06 ± 0.01 to 0.17 ± 0.03 ml · min
1 · cmH2O
1 · 100 g
1 (mean ± SE,
P < 0.05) but did not change in the
paced group. A Ca2+ ionophore,
A-23187, increased
Kf,c in both
control (10 µM; 0.05 ± 0.01 to 0.17 ± 0.05 ml · min
1 · cmH2O
1 · 100 g
1,
P < 0.05) and pace (5 µM; 0.06 ± 0.01 to 0.21 ± 0.07 ml · min
1 · cmH2O
1 · 100 g
1,
P < 0.05) lobes, indicating that
increasing intracellular Ca2+ is
sufficient to induce pulmonary microvascular permeability after pacing.
We conclude that during heart failure,
Ca2+ signaling within the
pulmonary microvascular endothelium is altered.
venous hypertension; microvascular permeability; capacitative calcium entry; pulmonary endothelium; capillary filtration coefficient
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