Increased phospholipase C activity after experimental brain injury

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✓ Phospholipase C activity was measured in 1000 × 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 times greater in cell fractions isolated from animals subjected to brain injury than in controls (p < 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.

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Address reprint requests to: Hermes A. Kontos, M.D., Ph.D., P.O. Box 281, Medical College of Virginia, Richmond, Virginia 23298.

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    Incorporation of phosphatidate (PA) into diacylglycerol (DG) by 1000 × G centrifuged fractions isolated from brain homogenates of control animals and animals subjected to experimental brain injury. Values are mean + standard error from six control and seven brain injury animals. This rate of incorporation is a direct measure of phospholipase C activity (see Materials and Methods section). Incorporation was significantly greater (p < 0.01) in animals subjected to brain injury than in controls.

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    Diacylglycerol-dependent incorporation of labeled cytidine diphosphate (CDP) choline into phosphatidylcholine (PC) by 1000 × G centrifuged fractions isolated from brain homogenates of control animals and animals subjected to brain injury. This rate is an indirect measure of phospholipase C activity. The rate of incorporation was significantly greater (p < 0.01) in the animals subjected to brain injury than in controls.

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