Increased phospholipase C activity after experimental brain injury.

Phospholipase C activity was measured in 1000 X G centrifuged cellular fractions isolated from cerebral cortical homogenates obtained from either control cats or cats subjected to experimental fluid-percussion brain injury. Phospholipase C activity was determined directly by measuring the Ca++-dependent conversion of membrane-bound, labeled phosphatidate to diacylglycerol or indirectly by measuring the diacylglycerol-dependent (brain diacylglycerol content) formation of phosphatidylcholine in the presence of labeled cytidine diphosphate (CDP) choline. Phospholipase C activity determined by either method was about two time greater in cell fractions isolated from animals subjected to brain injury than in controls (p less than 0.01). The brain injury-induced rise in phospholipase C activity may be responsible, at least in part, for generating diacylglycerol that may be a source of free arachidonic acid that stimulates prostaglandin synthesis. These changes may account for the rise in brain prostaglandin levels that has been demonstrated earlier to occur after this type of brain injury.