Hemorrhagic shock in swine: nitric oxide and potassium sensitive adenosine triphosphate channel activation.
BACKGROUND
To determine the role of nitric oxide and adenosine triphosphate-sensitive potassium (KATP) vascular channels in vascular decompensation during controlled hemorrhagic shock in swine.


METHODS
Thirty instrumented, anesthetized adolescent Yorkshire swine were subjected to controlled isobaric hemorrhage to a mean arterial pressure of 40 mmHg for 2 h (n = 6) or 4 h (n = 10) or 50 mmHg for 4 h (n = 8). An additional six animals were used as anesthetized instrumented time controls. During controlled hemorrhage, plasma and tissue samples were obtained every 30 to 60 min. Before euthanasia, tissue (carotid artery, lung, liver, and aorta) was obtained for analysis of nitrate concentrations and nitric oxide synthase activity. Isolated carotid artery ring reactivity to norepinephrine was also determined with and without glibenclamide.


RESULTS
Animals hemorrhaged to 40 mmHg decompensated earlier than animals hemorrhaged to 50 mmHg. Plasma nitrate concentrations and nitric oxide synthase activity rose consistently throughout hemorrhage in both groups. However, they were substantially higher in the mean arterial pressure 40 group. Constitutive nitric oxide synthase activity was the major contributor to total nitric oxide synthase activity throughout the protocol with only the animals maintained at 40 mmHg for 4 h showing evidence of inducible nitric oxide synthase activity. Profound KATP channel activation and hyporeactivity of isolated vessel rings to norepinephrine was not observed until 4 h after the initiation of hemorrhagic shock. Only those animals with inducible nitric oxide synthase activity showed a decreased response to norepinephrine, and this hyporeactivity was reversed with the KATP channel inhibitor, glibenclamide.


CONCLUSIONS
The data indicate that profound KATP activation associated with increased nitric oxide concentrations and inducible nitric oxide synthase induction is a key factor in vascular smooth muscle hyporeactivity characteristic of the late decompensatory phase of hemorrhagic shock in swine.
Anesthesia and Operative Service, Walter Reed Army Medical Center, Washington, D.C., USA.
Jeffrey B
JB
Musser
Timothy B
TB
Bentley
Scott
S
Griffith
Pushpa
P
Sharma
John E
JE
Karaian
Paul D
PD
Mongan
D018528:ATP-Binding Cassette Transporters; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism; D002339:Carotid Arteries / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D066298:In Vitro Techniques; D054086:KATP Channels; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000378:metabolism; D009566:Nitrates / Q000097:blood / Q000378:metabolism; D009569:Nitric Oxide / Q000097:blood / Q000378:metabolism / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D010101:Oxygen Consumption / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology*; D015221:Potassium Channels / Q000819:agonists*; D024661:Potassium Channels, Inwardly Rectifying; D012771:Shock, Hemorrhagic / Q000378:metabolism* / Q000503:physiopathology; D013552:Swine
D018528:ATP-Binding Cassette Transporters; D054086:KATP Channels; D009566:Nitrates; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; C092520:uK-ATP-1 potassium channel; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D011188:Potassium