Role of atp-sensitive potassium channels on modulating
diaphragmatic microvascular flow during hemorrhagic hypotension.
Chang, Han-Yu, Chang-Wen Chen, Tzuen-Ren Hsiue, and Cheng-Ren Chen.
Department of Internal Medicine, College of Medicine, National
Cheng Kung University, Tainan, Taiwan, R.O.C.
APStracts 3:0344H, 1996.
The effects of glibenclamide (GLB), a specific blocker of K+[ATP]
channels, and tetraethylammonium (TEA) on modulating regulation of
diaphragmatic microcirculation were assessed in anesthetized,
mechanically ventilated rats. With bicarbonate-buffered Ringer's
solution continuously suffusing the left hemi-diaphragm,
microcirculatory blood flow (QLDF) was recorded by laser-Doppler
flowmetry. Hemorrhagic hypotension (HH) was induced via bleeding into
a pressure reservoir. Five sets of experiments were performed. In set
1 (n=6), the vasodilator effect of diazoxide (3 x 10-4 M), was
abolished after 30-min suffusion with GLB, whereas the vasodilator
effect of sodium nitroprusside (3 x 10-6 M) remained the same. In set
2 (vehicle + HH, n=23), stepwise reduction of systemic arterial
pressure (PSYS) induced two distinct patterns of microvascular
responses. Regulation of QLDF could be observed in pattern A animals
at a range of PSYS from 113 to 52 mmHg, whereas QLDF in pattern B
animals rose progressively with declining PSYS. In set 3 (GLB + HH,
n=17), baseline values of QLDF were not significantly affected after
30-min suffusion of GLB (10-5 M). During hemorrhagic hypotension two
microvascular patterns similar to those in set 2 were observed. GLB
significantly potentiated the reduction of QLDF in pattern A animals.
In contrast, GLB had no effect on QLDF in pattern B animals. In set 4
(TEA + HH, n=17), similar microvascular responses, as compared to the
vehicle group, were observed during hemorrhagic hypotension after 30
-min suffusion of TEA (2 x 10-3 M). In set 5 (n=5), baseline values of
QLDF were not significantly altered during sham hypotension. We
conclude that 1) K+[ATP] channels are functional but not active in
resting diaphragmatic microcirculation; 2) K+[ATP] channels can
modulate regulation of microcirculation in the resting diaphragm
during hemorrhagic hypotension.
Received 8 February 1996; accepted in final form 20 July 1996.
APS Manuscript Number H1124-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996