Metabolic inhibition activates a non-selective current through connexin hemichannels in isolated ventricular myocytes.
Intracellular Na(+)accumulation and K(+)loss play important roles in the pathogenesis of arrhythmias and injury in the ischemic heart. We investigated the role of metabolically sensitive connexin hemichannels as a potential route for Na(+)influx and K(+)efflux during ischemia, using dye uptake and electrophysiological measurements to assay hemichannel activity in isolated rabbit ventricular myocytes. Consistent with the known size selectivity of connexin hemichannels,;50% of myocytes exposed to either low extracellular Ca(2+)(an established method for opening connexin hemichannels) or to metabolic inhibitors (a recently described method for opening hemichannels) accumulated fluorescent dyes with <1000 MW (propidium iodide and calcein), but excluded a larger dye with 1500-3000 MW (dextran-rhodamine). Using the whole cell patch clamp technique, we found that metabolic inhibitors activated a non-selective current permeant to both small and large cations, and blocked by La(3+), similar to the properties of connexin 43 when overexpressed in human embryonic kidney (HEK) cells. These findings indicate that isolated cardiac myocytes endogenously express metabolically-sensitive connexin hemichannels. If activated during ischemia, these hemichannels could contribute significantly to altered ionic fluxes promoting arrhythmias and myocardial injury.
Kondo
R P
RP
UCLA Cardiovascular Research Laboratory, UCLA School of Medicine, Los Angeles, CA 90095, USA.
Wang
S Y
SY
John
S A
SA
Weiss
J N
JN
Goldhaber
J I
JI
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002412:Cations; D002460:Cell Line; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D018031:Connexin 43 / Q000378:metabolism; D017630:Connexins / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004594:Electrophysiology; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D006352:Heart Ventricles / Q000378:metabolism*; D006801:Humans; D007202:Indicators and Reagents / Q000494:pharmacology; D007811:Lanthanum / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D017202:Myocardial Ischemia / Q000378:metabolism; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011817:Rabbits; D012402:Rotenone / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D013997:Time Factors; D014475:Uncoupling Agents / Q000494:pharmacology
D002412:Cations; D002614:Chelating Agents; D018031:Connexin 43; D017630:Connexins; D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D014475:Uncoupling Agents; D012402:Rotenone; D004533:Egtazic Acid; D007811:Lanthanum; D012964:Sodium; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium