Nonanticoagulant heparin reduces myocyte Na+ and Ca2+ loading during simulated ischemia and decreases reperfusion injury.
Heparin desulfated at the 2-O and 3-O positions (ODSH) decreases canine myocardial reperfusion injury. We hypothesized that this occurs from effects on ion channels rather than solely from anti-inflammatory activities, as previously proposed. We studied closed-chest pigs with balloon left anterior descending coronary artery occlusion (75-min) and reperfusion (3-h). ODSH effects on [Na(+)](i) (Na Green) and [Ca(2+)](i) (Fluo-3) were measured by flow cytometry in rabbit ventricular myocytes after 45-min of simulated ischemia [metabolic inhibition with 2 mM cyanide, 0 glucose, 37 degrees C, pacing at 0.5 Hz; i.e., pacing-metabolic inhibition (PMI)]. Na(+)/Ca(2+) exchange (NCX) activity and Na(+) channel function were assessed by voltage clamping. ODSH (15 mg/kg) 5 min before reperfusion significantly decreased myocardial necrosis, but neutrophil influx into reperfused myocardium was not consistently reduced. ODSH (100 microg/ml) reduced [Na(+)](i) and [Ca(2+)](i) during PMI. The NCX inhibitor KB-R7943 (10 microM) or the late Na(+) current (I(Na-L)) inhibitor ranolazine (10 microM) reduced [Ca(2+)](i) during PMI and prevented effects of ODSH on Ca(2+) loading. ODSH also reduced the increase in Na(+) loading in paced myocytes caused by 10 nM sea anemone toxin II, a selective activator of I(Na-L). ODSH directly stimulated NCX and reduced I(Na-L). These results suggest that in the intact heart ODSH reduces Na(+) influx during early reperfusion, when I(Na-L) is activated by a burst of reactive oxygen production. This reduces Na(+) overload and thus Ca(2+) influx via NCX. Stimulation of Ca(2+) extrusion via NCX later after reperfusion may also reduce myocyte Ca(2+) loading and decrease infarct size.
School of Medicine, Division of Cardiology, University of Utah Medical Center, Salt Lake City, UT 84132, USA. William.Barry@hsc.utah.edu
William H
WH
Barry
Xiu Q
XQ
Zhang
Michael E
ME
Halkos
Jakob
J
Vinten-Johansen
Noriko
N
Saegusa
Kenneth W
KW
Spitzer
Nobuhiro
N
Matsuoka
Michael
M
Sheets
Narayanam V
NV
Rao
Thomas P
TP
Kennedy
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D002304:Cardiac Pacing, Artificial; D002469:Cell Separation; D003326:Coronary Circulation / Q000187:drug effects; D005260:Female; D006493:Heparin / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009203:Myocardial Infarction / Q000473:pathology; D017202:Myocardial Ischemia / Q000378:metabolism*; D015428:Myocardial Reperfusion Injury / Q000473:pathology / Q000517:prevention & control*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism*; D009195:Peroxidase / Q000378:metabolism; D020011:Protective Agents; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors / Q000378:metabolism; D013552:Swine
D015220:Calcium Channels; D020011:Protective Agents; D015222:Sodium Channels; D019831:Sodium-Calcium Exchanger; D006493:Heparin; D012964:Sodium; D009195:Peroxidase; D002118:Calcium