Swelling-activated chloride current is activated in guinea pig cardiomyocytes from endotoxic shock.
OBJECTIVE
Myocardial swelling occurs during endotoxic shock. The hypothesis that swelling-activated Cl- current (ICl,swell) activates during endotoxic shock was tested.


METHODS
Endotoxic shock was induced by intravenous lipopolysaccharides (10 mg/kg) in guinea pigs. The effects of ICl,swell blockers on the cardiac action potentials in papillary muscles and on the ICl,swell in single ventricular myocytes were tested.


RESULTS
Action potential duration (APD) at 90% of repolarization (APD90) was significantly shortened after 5-h endotoxic shock in guinea pig papillary muscles. I(Cl,swell) blockers, 9-anthracene carboxylic acid (9-AC) and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), dose-dependently prolonged the shortened APD90. Inducible nitric oxide synthase (iNOS) inhibitors, L-N6-(1-iminoethyl) lysine (L-NIL) and N-[[3-(aminomethyl)phenyl]methyl]-ethanimidamide (1400 W), also prolonged the APD90. Protein kinase C (PKC) activators, 4beta-phorbol 12-myristate 13-acetate (PMA) and phorbol 12,13-didecanoate (PDD), also prolonged the APD. The addition of glibenclamide (an ATP-sensitive K+ channel blocker) on top of these ICl,swell blockers hastened the recovery of APD90 compared to the use of ICl,swell blockers alone. Whole-cell voltage-clamp study in single ventricular myocytes from endotoxic shock heart disclosed activation of a DIDS- and 9-AC-sensitive current. These currents displayed outward rectification with reversal potentials similar to the calculated Nernst potential for Cl-. The reversal potentials tracked the ECl closely when the Cl- gradient was changed, suggesting that Cl- was the major charged carrier.


CONCLUSIONS
We have shown for the first time that ICl,swell activates in guinea pig heart in endotoxic shock. The change in this membrane current, together with the activation of ATP-sensitive K+ current, contributes to the electrophysiological derangement in endotoxic shock.
Chiang
Chern-En
CE
Division of Cardiology, Taipei Veterans General and National Yang-Ming University, Taipei, Taiwan. cechiang@vghtpe.gov.tw
Luk
Hsiang-Ning
HN
Wang
Tsui-Min
TM
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000200:Action Potentials / Q000502:physiology; D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006168:Guinea Pigs; D006352:Heart Ventricles; D008070:Lipopolysaccharides; D008297:Male; D023421:Models, Animal; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052247:Nitric Oxide Synthase Type II; D018408:Patch-Clamp Techniques; D010703:Phorbol Esters / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D012772:Shock, Septic / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000873:Anthracenes; D018118:Chloride Channels; D008070:Lipopolysaccharides; D010703:Phorbol Esters; C008876:phorbol-12,13-didecanoate; C010030:9-anthroic acid; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid