Calcium-dependent proteolytic activity in hypoxic rat brain.

The effect of hypoxia (7% oxygen in nitrogen) on Ca2+-activated protease (/u- and mCANP) in the rat brain has been studied. Hypoxia changed the intracellular distribution of CANPs without affecting the total calcium dependent proteolytic activity. The 3-fold rise of the activity of mCANP bound to synaptosomal membranes and less pronounced elevation in mitochondrial and microsomal fractions is compensated by corresponding drop of mCANP activity in cytosol. The changes of /uCANP under hypoxia were less expressed and their direction was opposite to mCANP. Additionally the susceptibility of brain membrane proteins to mCANP was tested. Our results show that proteins from the brains of animals submitted to hypoxic conditions are more susceptible to CANP than those from control animals. Thus, it is suggested that hypoxia results in some physico-chemical changes of membranes which render the membranes more sensitive to CANP.