Plasminogen activator in the rodent brain.

The cellular origin(s), the biochemical properties and the developmental pattern of the protease plasminogen activator (PA) were investigated in the rodent brain. PA activity was localized in frozen brain sections by a novel autoradiography technique. PA levels and electrophoretic mobility were determined in homogenates prepared from major regions of the developing and the mature brain, and both the localization and the specific activity of the enzyme were examined in X-irradiated brain regions. PA activity was shown to be correlated with cell bodies in neuronal-enriched regions and also with endothelial, meningeal and ependymal layers. PA levels increased in a transient manner and at different rates and time periods in the various brain regions that were analyzed. PA in neuronal, but not in epithelial cell layers was affected by X-irradiation and one of the brain PA species had a similar molecular weight of that of neuroblastoma cells. Our findings suggest that in the brain PA is produced by neurons and by epithelial cells, and that it may have additional functions to that of thrombolysis both in the developing and the mature brain.