Brain protease activity after experimental head injury.

In an experimental series on twelve cats, activity changes of brain cell proteolytic activity were measured two hours after a blunt head injury without hematoma or contusions. Protease activity was estimated in two different brain tissue homogenate supernatants containing total soluble and only cytoplasmic activity without proteases in cell organelles, respectively. Total activity was doubled two hours after injury in the acid and the neural pH-range, in comparison to control values. Free soluble activity was doubled in the acid and increased to the threefold value in the neutral range. From these data, it seems that two different changes appear in lysosomes, the enzyme-reservoir of the cell: (1) Enzyme-synthesis is increased after trauma, measured as augmentation of total soluble protease activity in our experiments; (2) Breakage or increased permeability of lysosomes lead to augmentation of especially neutral proteases in the cytoplasm followed by the well known autolytic areas of generalized traumatic brain edema.