RESULTS: The
calcium-independent phospholipase A2 activity showed the same pH, temperature and
calcium sensitivity in control and ischemic (15 min of
ischemia) lyophilized myocardial tissue. Incubation of control and ischemic tissue showed no difference in the rate of accumulation of
lysophospholipids when the ischemic tissue was obtained from hearts exposed to 15 min of
ischemia (107 +/- 4 vs 111 +/- 7 nmol/g dry wt x min,
ischemia versus control, mean +/- s.e.m., n = 8), but a significant decrease was noticed in tissue from hearts that had been exposed to 60 min of
ischemia (31 +/- 9 vs 86 +/- 18 nmol/g dry wt x min, P < 0.05, n = 4). The decreased
phospholipase A2 activity in tissue exposed to 60 min of
ischemia was not due to enhanced metabolism of the
lysophospholipids (84 +/- 15 vs 79 +/- 8 nmol/g dry wt x min, n = 4). The
calcium-independent phospholipase A2 activity was considerably lower in fresh myocardial tissue compared with lyophilized tissue, but comparison of control and ischemic fresh tissue gave results comparable to those found using lyophilized tissue. The myocardial
calcium-independent phospholipase A2 activity showed no
plasmalogen selectivity in either control or ischemic myocardium.
CONCLUSIONS: