title: Hemichannels in cardiomyocytes open transiently during ischemia and contribute to reperfusion injury following brief ischemia.
abstract: The aim of this study was to investigate changes in hemichannel activity during in vitro simulated ischemia [oxygen-glucose deprivation (OGD)] and the contribution of hemichannels to ischemia-reperfusion injury in rat neonatal cardiomyocytes. Dye uptake assays showed that hemichannels opened as OGD progressed, peaking after 1 h, and then closed, returning to the pre-OGD state after 2 h of OGD. The increase in dye uptake after 1 h of OGD was inhibited by hemichannel blockers (lanthanum chloride and a connexin 43 mimetic peptide, Gap26). During OGD, intracellular Ca(2+) concentration ([Ca(2+)](i)) began to increase after 1 h and reached several micromolar after 2 h. After 1 h of OGD, Gap26 inhibited the increases in hemichannel activity and [Ca(2+)](i). In contrast, dantrolene [an endo(sarco)plasmic reticulum Ca(2+) release inhibitor] suppressed the increase in [Ca(2+)](i), but not in hemichannel activity. After 2 h of OGD, the combined administration of 2',4'-dichlorobenzamil and dantrolene reduced [Ca(2+)](i) to <1 microM and increased hemichannel activity to the level attained after 1 h of OGD. Simulated ischemia-reperfusion, induced by 1 h of OGD followed by 2 h of recovery, reduced cell viability to 54% of the control level. The addition of Gap26 to OGD medium improved viability to 80% of the control level. In conclusion, this study demonstrated that 1) hemichannels open transiently during OGD, 2) closure of hemichannels, but not their opening, is regulated by an increase in [Ca(2+)](i) during OGD, and 3) open hemichannels contribute to cell injury during recovery from OGD.
authors.affiliation: Department of Forensic Medicine, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. kaori@m.u-tokyo.ac.jp
authors.forename: Kaori
authors.initials: K
authors.lastname: Shintani-Ishida
authors.forename: Koichi
authors.initials: K
authors.lastname: Uemura
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Yoshida
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D017630:Connexins / Q000037:antagonists & inhibitors / Q000502:physiology*; D003620:Dantrolene / Q000494:pharmacology; D019157:Ischemic Preconditioning, Myocardial; D007811:Lanthanum / Q000494:pharmacology; D009125:Muscle Relaxants, Central / Q000494:pharmacology; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000503:physiopathology*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology*; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D017630:Connexins; C514423:Gap 26 peptide; D009125:Muscle Relaxants, Central; D010455:Peptides; C028521:lanthanum chloride; D007811:Lanthanum; D003620:Dantrolene; D002118:Calcium