Ischemic preconditioning (IP) may protect the lung from
ischemia-reperfusion (I/R) injury following cardiopulmonary by-pass and lung or
heart transplantation. The present study was undertaken to investigate the role of
ATP-dependent
potassium channels (K(
ATP)) in IP in the isolated
buffer-perfused rat lung (IBPR) under conditions of elevated pulmonary
vasoconstrictor tone (PVT). Since pulmonary arterial perfusion flow and left atrial pressure were constant, changes in pulmonary arterial pressure (PAP) directly reflect changes in pulmonary vascular resistance (PVR). When compared to control value, the pulmonary
vasodilator responses to
histamine and
acetylcholine (ACh) following 2 h of hypothermic
ischemia were significantly attenuated, whereas the pulmonary
vasodilator response to
sodium nitroprusside (SNP) was not altered. IP in the form of two cycles of 5 min of
ischemia and reperfusion applied prior to the two-hour interval of
ischemia, prevented the decrease in the pulmonary
vasodilator responses to
histamine and ACh. Pretreatment with
glybenclamide (GLB) or
HMR-1098, but not
5-hydroxydecanoic acid (5-HD), prior to IP abolished the protective effect of IP. In contrast, GLB or 5-HD did not significantly alter the pulmonary
vasodilator response to
histamine without IP pretreatment. The present data demonstrate that IP prevents impairment of endothelium-dependent
vasodilator responses in the rat pulmonary vascular bed. The present data further suggest that IP may alter the mediation of the pulmonary
vasodilator response to
histamine and thereby trigger a mechanism dependent on activation of sarcolemmal, and not mitochondrial, K(
ATP) channels to preserve endothelial-dependent
vasodilator responses and protect against I/R injury in the lung.