Calcium-activated neutral protease activities in brain trauma.

This paper investigates the level of cytosolic and synaptosomal forms of calcium activated neutral protease activities in the normal brain and their changes following a freezing lesion in the rabbit. From 1 to 24 hours post lesion we observe a progressive disappearing of the enzyme activities from the cytosolic compartment and concurrently their increase in the membranal fraction. These changes are likely to be due to a rise in intracellular calcium concentration, a well documented consequence of many cellular insults. The specific role of the activation of calpain activities in the pathophysiology of trauma is discussed, an enhancement of excitotoxic mechanisms is proposed.