In Vivo Evidence for Nitric Oxide–Mediated Calcium-Activated Potassium-Channel Activation During Human Endotoxemia

Background— During septic shock, the vasoconstrictor response to norepinephrine is seriously blunted. Animal experiments suggest that hyperpolarization of smooth muscle cells by opening of potassium (K) channels underlies this phenomenon. In the present study, we examined whether K-channel blockers and/or nitric oxide (NO) synthase inhibition could restore norepinephrine sensitivity during experimental human endotoxemia. Methods and Results— Volunteers received 2 ng/kg Escherichia coli endotoxin intravenously. Forearm blood flow (FBF) was measured with venous occlusion plethysmography. Infusion of 4 dose steps of norepinephrine into the brachial artery decreased the FBF ratio (ratio of FBF in the experimental arm to FBF in the control arm) to 84±4%, 70±4%, 55±4%, and 38±4% (mean±SEM) of its baseline value. After endotoxin administration, norepinephrine-induced vasoconstriction was attenuated (FBF ratio, 101±4%, 92±4%, 83±6%, and 56±7%; n=30; P=0.0018; pooled data). Intrabrachial infusion of the K-channel blocker tetraethylammonium (TEA) completely restored the vasoconstrictor response to norepinephrine from 104±5%, 93±7%, 93±12%, and 69±12% to 89±9%, 73±4%, 59±5%, and 46±8% (n=6; P=0.045). Other K-channel blockers did not affect the response to norepinephrine. The NO synthase inhibitor NG-monomethyl-l-arginine (L-NMMA; 0.2 mg · min−1 · dL−1 intra-arterially) also restored the norepinephrine sensitivity. In the presence of L-NMMA, TEA did not have an additional effect on the norepinephrine-induced vasoconstriction (n=6; P=0.9). Conclusions— The K-channel blocker TEA restores the attenuated vasoconstrictor response to norepinephrine during experimental human endotoxemia. Coadministration of L-NMMA abolishes this potentiating effect of TEA, suggesting that NO mediates the endotoxin-induced effect on vascular K channels. In the absence of an effect of the selective adenosine triphosphate–dependent K-channel blocker tolbutamide, we conclude that the blunting effect of endotoxin on norepinephrine-induced vasoconstriction is caused by NO-mediated activation of calcium-activated K channels in the vascular wall.

[1]  M. Singer,et al.  Reversal of life-threatening, drug-related potassium-channel syndrome by glibenclamide , 2005, The Lancet.

[2]  L. Kelly,et al.  Effect of Potassium Channel and Cytochrome P450 Inhibition on Transient Hypotension and Survival during Lipopolysaccharide-Induced Endotoxic Shock in the Rat , 2005, Pharmacology.

[3]  M. Singer,et al.  The pore‐forming subunit of the KATP channel is an important molecular target for LPS‐induced vascular hyporeactivity in vitro , 2005, British journal of pharmacology.

[4]  J. G. van der Hoeven,et al.  ACTIVATION OF THE ATP-DEPENDENT POTASSIUM CHANNEL ATTENUATES NOREPINEPHRINE-INDUCED VASOCONSTRICTION IN THE HUMAN FOREARM , 2004, Shock.

[5]  D. Webb,et al.  Comparison of two plethysmography systems in assessment of forearm blood flow. , 2004, Journal of applied physiology.

[6]  J. Bakker,et al.  Administration of the nitric oxide synthase inhibitor NG-methyl-l-arginine hydrochloride (546C88) by intravenous infusion for up to 72 hours can promote the resolution of shock in patients with severe sepsis: Results of a randomized, double-blind, placebo-controlled multicenter study (study no. 144- , 2004, Critical care medicine.

[7]  J. Bakker,et al.  Multiple-center, randomized, placebo-controlled, double-blind study of the nitric oxide synthase inhibitor 546C88: Effect on survival in patients with septic shock* , 2004, Critical care medicine.

[8]  M. Wolzt,et al.  Inflammation-induced vasoconstrictor hyporeactivity is caused by oxidative stress. , 2003, Journal of the American College of Cardiology.

[9]  M. Joyner,et al.  Blunted Sympathetic Vasoconstriction in Contracting Skeletal Muscle of Healthy Humans: is Nitric Oxide Obligatory? , 2003, The Journal of physiology.

[10]  Pritpal S Tamber,et al.  The Surviving Sepsis Campaign: raising awareness to reduce mortality , 2003, Critical care.

[11]  M. Netea,et al.  TNFα AND IL-1β EXERT NO DIRECT VASOACTIVITY IN HUMAN ISOLATED RESISTANCE ARTERIES , 2002 .

[12]  T. B. Paiva,et al.  Different mechanism of LPS‐induced vasodilation in resistance and conductance arteries from SHR and normotensive rats , 2002, British journal of pharmacology.

[13]  U. Prabhakar,et al.  Simultaneous quantification of proinflammatory cytokines in human plasma using the LabMAP assay. , 2002, Journal of immunological methods.

[14]  J. Assreuy,et al.  Differential Involvement of Guanylate Cyclase and Potassium Channels in Nitric Oxide-Induced Hyporesponsiveness to Phenylephrine in Endotoxemic Rats , 2002, Shock.

[15]  M. Wolzt,et al.  Adrenoceptor Hyporeactivity Is Responsible for Escherichia coli Endotoxin‐Induced Acute Vascular Dysfunction in Humans , 2002, Arteriosclerosis, thrombosis, and vascular biology.

[16]  M. Netea,et al.  TNFalpha and IL-1beta exert no direct vasoactivity in human isolated resistance arteries. , 2002, Cytokine.

[17]  J. Eldstrom,et al.  Lipopolysaccharide can activate BK channels of arterial smooth muscle in the absence of iNOS expression. , 2001, Biochimica et biophysica acta.

[18]  D. Landry,et al.  The pathogenesis of vasodilatory shock. , 2001, The New England journal of medicine.

[19]  G. Clermont,et al.  Epidemiology of severe sepsis in the United States: Analysis of incidence, outcome, and associated costs of care , 2001, Critical care medicine.

[20]  Alun D. Hughes,et al.  In vivo evidence for KCa channel opening properties of acetazolamide in the human vasculature , 2001, British journal of pharmacology.

[21]  S. Yang,et al.  Hyperpolarization contributes to vascular hyporeactivity in rats with lipopolysaccharide-induced endotoxic shock. , 2000, Life sciences.

[22]  I. Gartside,et al.  Description and validation of a novel liquid metal-free device for venous congestion plethysmography. , 2000, Journal of applied physiology.

[23]  M. Yen,et al.  Abnormal activation of K+ channels in aortic smooth muscle of rats with endotoxic shock: electrophysiological and functional evidence , 2000, British journal of pharmacology.

[24]  J. Assreuy,et al.  Involvement of soluble guanylate cyclase and calcium-activated potassium channels in the long-lasting hyporesponsiveness to phenylephrine induced by nitric oxide in rat aorta , 2000, Naunyn-Schmiedeberg's Archives of Pharmacology.

[25]  D. Annane,et al.  Compartmentalised inducible nitric-oxide synthase activity in septic shock , 2000, The Lancet.

[26]  M. Yen,et al.  Role of nitric oxide and K+-channels in vascular hyporeactivity induced by endotoxin , 1999, Naunyn-Schmiedeberg's Archives of Pharmacology.

[27]  L S Murray,et al.  How reproducible is bilateral forearm plethysmography? , 1998, British journal of clinical pharmacology.

[28]  L. Clapp,et al.  Abnormal activation of K+ channels underlies relaxation to bacterial lipopolysaccharide in rat aorta. , 1996, Biochemical and biophysical research communications.

[29]  C. Szabó,et al.  Inhibition of ATP-activated potassium channels exerts pressor effects and improves survival in a rat model of severe hemorrhagic shock. , 1996, Shock.

[30]  G. Vanelli,et al.  Glibenclamide, a blocker of ATP‐sensitive potassium channels, reverses endotoxin‐induced hypotension in pig , 1995, Experimental physiology.

[31]  S. Archer,et al.  Nitric oxide and cGMP cause vasorelaxation by activation of a charybdotoxin-sensitive K channel by cGMP-dependent protein kinase. , 1994, Proceedings of the National Academy of Sciences of the United States of America.

[32]  R. Cohen,et al.  Nitric oxide directly activates calcium-dependent potassium channels in vascular smooth muscle , 1994, Nature.

[33]  D. Landry,et al.  The ATP-sensitive K+ channel mediates hypotension in endotoxemia and hypoxic lactic acidosis in dog. , 1992, The Journal of clinical investigation.

[34]  J. Kovacs,et al.  The cardiovascular response of normal humans to the administration of endotoxin. , 1989, The New England journal of medicine.

[35]  J E Parrillo,et al.  Serial cardiovascular variables in survivors and nonsurvivors of human septic shock: heart rate as an early predictor of prognosis. , 1987, Critical care medicine.

[36]  Timmermans Pb,et al.  Postsynaptic alpha 1- and alpha 2-adrenoceptor blocking properties of (dihydro)quinidine and (dihydro)quinine. , 1983 .

[37]  P. Timmermans,et al.  Postsynaptic alpha 1- and alpha 2-adrenoceptor blocking properties of (dihydro)quinidine and (dihydro)quinine. , 1983, Arzneimittel-Forschung.

[38]  S. Hoobler,et al.  STUDIES ON VASOMOTOR TONE. I. THE EFFECT OF THE TETRA-ETHYLAMMONIUM ION ON THE PERIPHERAL BLOOD FLOW OF NORMAL SUBJECTS. , 1949, The Journal of clinical investigation.

[39]  K. Campbell,et al.  The use of tetraethylammonium in peripheral vascular disease and causalgic states; a new method for producing blockade of the autonomic ganglion. , 1947, Surgery.

[40]  Campbell Kn,et al.  The use of tetraethylammonium in peripheral vascular disease and causalgic states; a new method for producing blockade of the autonomic ganglion. , 1946 .