Phospholipase A2 secretion during intestinal graft ischemia.

The time-dependent appearance of phospholipase A2 (PLA2) activity in the preservation media of ischemic rat intestinal grafts is described. In controls, Ca2+-dependent, secretory PLA2 activity accumulated rapidly during the first 6 hr of ischemia, followed by a linear increase for up to 48 hr. LDH levels, by contrast, increased linearly throughout the 48 hr of ischemia. Addition of inhibitors of PLA2, cyclooxygenase, and lipooxygenase blocked accumulation of PLA2, but not LDH. PX-13, a novel PLA2 inhibitor, was most effective: 40 microM inhibited release by 86%, while 25 microM indomethacin (cyclooxygenase blocker) or nordihydroguiaretic acid (lipooxygenase blocker) inhibited 41 and 36%, respectively. That appearance of PLA2 activity, but not LDH, is attenuated by inhibitors of the eicosanoid cascade suggests a secretory event rather than leakage from dying cells. The secreted PLA2 is most likely the proinflammatory sPLA2 that has been implicated as a stress-induced protein and priming agent in ischemia-reperfusion injury.