Identification of the changes in phospholipase C isozymes in ischemic–reperfused rat heart

Phospholipase C (PLC) influences cardiac function. This study examined PLC isozymes of the cardiac sarcolemma (SL) membrane and in the cytosol compartment in isolated perfused rat hearts subjected to global ischemia for 30 min followed by up to 30 min of reperfusion. Although the total SL PLC activity was decreased in ischemia and increased upon reperfusion, differential changes in PLC isozymes were detected. PLC β1 mRNA and SL protein abundance and activity were increased in ischemia, with concomitant decreases in activity and protein level in the cytosol. On the other hand, upon reperfusion, PLC β1 activity was decreased, but remained higher than control values. Although no change in the PLC δ1 mRNA level in ischemia was detected, SL PLC δ1 activity and content were depressed. Furthermore, in the cytosol, PLC δ1 activity was increased, but the protein level decreased. SL PLC γ1 activity was decreased, independent of gene expression and protein content; however, decreases in the activity and protein abundance were detected in the cytosol. Increases in PLC γ1 and δ1 activities occurred upon reperfusion, but were not accounted for by altered mRNA and protein levels. The results indicate that ischemia–reperfusion induces differential changes in PLC isozymes.