It has been reported that myocardial
glutathione content is decreased during
ischemia-reperfusion, but the mechanism of
glutathione depletion has remained unclear. The present study tested whether osmotic stress is involved in the
glutathione depletion during
ischemia. Six hours of hypoxic
acidosis with either high CO(2) tension or low HCO(3)(-) concentration, which simulates the ischemic condition, resulted in a significant decrease of
glutathione content and the
glutathione depletion was prevented by hyperosmolarity. High-CO(2)
acidosis alone without
hypoxia induced a similar degree of
glutathione depletion. Intracellular pH was lowered by high-CO(2)
acidosis to 6.41 ± 0.03 in 15 min. Meanwhile, the cell size gradually increased and reached ∼110% in 10 min and the increased cell size was maintained for at least 30 min, which was also prevented by hyperosmolarity. Subsequent experiments observed the effects of simulated reperfusion on the
glutathione content. Measured in 1 h after the hypoxic acidotic reperfusion, the
glutathione content was further decreased compared to the level at the end of
ischemia, which was not suppressed by increasing the osmolarity of reperfusion
solution. The degree of
glutathione depletion during hypoxic reperfusion with normal pH was similar to the hypoxic acidotic reperfusion group. On the other hand, normoxic reperfusion was not accompanied by further depletion of
glutathione content. Based on these results, it was concluded that
ischemia induces the
glutathione depletion via osmotic stress, which results from intracellular acidification, and the
glutathione content is further decreased during reperfusion through a mechanism other than
oxygen toxicity.