Fig. 4. (A ) Ischemia causes an increase in inorganic phosphate (Pi) (open squares ) and anesthetic preconditioning (APC) limits the Pi increases (closed squares ) during ischemia and improves the recovery during reperfusion in young adult hearts (*P < 0.05). (B ) Ischemia causes an increase in Pi (open circles ) and APC does not limit the Pi increases (closed circles ) in middle-aged hearts. (C ) Ischemia causes an increase in Pi (open triangles ) and APC does not limit the Pi increase (closed triangles ) during ischemia in aged hearts. n = 6/group. * APC versus  control.