Role of ATP-conductive anion channel in ATP release from neonatal rat cardiomyocytes in ischaemic or hypoxic conditions.
It is known that the level of ATP in the interstitial spaces within the heart during ischaemia or hypoxia is elevated due to its release from a number of cell types, including cardiomyocytes. However, the mechanism by which ATP is released from these myocytes is not known. In this study, we examined a possible involvement of the ATP-conductive maxi-anion channel in ATP release from neonatal rat cardiomyocytes in primary culture upon ischaemic, hypoxic or hypotonic stimulation. Using a luciferin-luciferase assay, it was found that ATP was released into the bulk solution when the cells were subjected to chemical ischaemia, hypoxia or hypotonic stress. The swelling-induced ATP release was inhibited by the carboxylate- and stilbene-derivative anion channel blockers, arachidonic acid and Gd3+, but not by glibenclamide. The local concentration of ATP released near the cell surface of a single cardiomyocyte, measured by a biosensor technique, was found to exceed the micromolar level. Patch-clamp studies showed that ischaemia, hypoxia or hypotonic stimulation induced the activation of single-channel events with a large unitary conductance (approximately 390 pS). The channel was selective to anions and showed significant permeability to ATP4- (PATP/PCl approximately 0.1) and MgATP2- (PATP/PCl approximately 0.16). The channel activity exhibited pharmacological properties essentially identical to those of ATP release. These results indicate that neonatal rat cardiomyocytes respond to ischaemia, hypoxia or hypotonic stimulation with ATP release via maxi-anion channels.
Department of Cell Physiology, National Institute for Physiological Sciences, Myodaiji-cho, Okazaki 444-8585, Japan.
Amal K
AK
Dutta
Ravshan Z
RZ
Sabirov
Hiromi
H
Uramoto
Yasunobu
Y
Okada
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D015687:Cell Hypoxia / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D007038:Hypotonic Solutions / Q000494:pharmacology; D007473:Ion Channels / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D009997:Osmotic Pressure / Q000187:drug effects; D016716:PC12 Cells; D051381:Rats; D017208:Rats, Wistar
D007038:Hypotonic Solutions; D007473:Ion Channels; D000255:Adenosine Triphosphate