Abstract
ATP conductive maxi-anion channels are functionally expressed in rat cardiomyocytes and activated in hypotonic, hypoxic or ischemic conditions. In the present study, using a newly developed Scanning Ion Conductance Microscopy (SICM) technique combined with patch-clamp, we studied the spatial distribution of maxi-anion channels over the surface of sarcolemma of primary cultured neonatal rat cardiomyocytes and isolated adult cardiomyocytes. In primary cultured rat cardiomyocytes, maxi-anion channels were found to be predominantly expressed around the center of the cell body compared to the cell extensions. Using a P2X-receptor-based biosensor technique, it was found that the local concentration of ATP released in response to hypotonic stress was higher around the cell center compared to that at cell extensions. In isolated adult rat cardiomyocytes, maxi-anion channel activity was observed when a fine-tipped patch pipettes were giga-sealed at the grooved areas of sarcolemma using a conventional patch-clamp method. After taking a 3-D image of isolated cell by SICM technique, we specifically patched T-tubules, Z-grooves and scallop crest areas. We found that maxi-anion channels are predominantly expressed in T-tubules and Z-groove areas, but not in scallop crests, in adult cardiomyocytes. The results obtained indicate that maxi-anion channels are heterogeneously expressed over the surface of the rat cardiac sarcolemma. [J Physiol Sci. 2006;56 Suppl:S154]
