Alterations of phospholipase C isozymes in rat cerebral cortex through hyperoxia

The effect of hyperoxia on the level of three phospholipase C (PLC) isozyme s (beta1, gamma1, delta1) was assessed in the rat cerebral cortex. When the rats were exposed to 100% oxygen for 60 h, there was a significant reducti on in the catalytic activity of low molecular weight phosphotyrosine phosph atase, which was susceptible to activity loss under oxidative stress. The r esult suggests that oxidative stress is induced in the rat cerebral cortex through hyperoxia. The protein levels of PLC-beta1 and -delta1 were signifi cantly increased in the cerebral cortex where oxidative stress had been ind uced, although that of PLC-gamma1 was not altered. There was no significant difference in the total PLC activity of the cerebral cortex between hypero xia and control rats. Using gel filtration chromatography, it was revealed that the PLC-beta1 activity in the cerebral cortex of the hyperoxia rats wa s higher than that in the control rats, but the PLC-delta1 activity in the former did not differ from that in the latter, despite an increase in the P LC-delta1 protein level. These findings suggest that the PLC-beta1 and -del ta1 protein levels of brain tissues are increased by oxidative stress, and that the increased PLC-delta1 molecule is less active.