METABOLIC COUPLING OF GLUTATHIONE BETWEEN MOUSE AND QUAIL CARDIAC MYOCYTES AND ITS PROTECTIVE ROLE AGAINST OXIDATIVE STRESS

Cultured quail myocytes were much more resistant to H2O2 toxicity than cultured mouse myocytes. The intracellular concentration of glutathio ne ([GSH](i)) and the activity of gamma-glutamylcysteine synthetase (g amma-GCS) in quail heart cells were about five and three times higher, respectively, than in mouse heart cells, although catalase and glutat hione peroxidase (GSH(px)) activity was similar in both. Preloading of gamma-glutamylcysteine monoethyl ester (gamma-GCE), a membrane-permea ting GSH precursor, increased the H2O2 resistance of cultured mouse my ocytes. These observations suggest that the high [GSH](i) and the high activity of gamma-GCS in quail myocytes are responsible for their hig h resistance to H2O2. Both H2O2 sensitivity and [GSH](i) of mosaic she ets composed of equal amounts of mouse and quail myocytes approximated those of sheets composed entirely of quail myocytes. From these obser vations, it is hypothesized that GSH was transferred from quail myocyt es to mouse myocytes, probably through gap junctions between them, and that quail myocytes resynthesized GSH by a feedback mechanism, thus m aintaining their intracellular GSH levels. When the fluorescent dye lu cifer yellow was injected into a beating quail myocyte in a mosaic she et, it spread to neighboring mouse myocytes but not to neighboring L c ells (a cell line derived from mouse connective tissue). These observa tions indicate the existence of gap junctions in the region of cell co ntact between mouse and quail myocytes but not between quail myocytes and L cells. When quail myocytes preloaded with [H-3]gamma-GCE were co cultured with mouse myocytes and L cells, the radioactivity was transm itted to neighboring mouse myocytes but not L cells. These observation s show that GSH and/or its precursors can be transmitted from quail my ocytes to mouse myocytes through gap junctions and that this can prote ct mouse myocytes from H2O2 toxicity. Mouse myocyte sheets composed of 10(4) cells or more showed higher resistance to H2O2 toxicity than si ngle isolated mouse myocytes. Metabolic coupling of GSH between myocyt es may contribute at least in part to this high resistance of the cell sheets.