Postnatal development of aminopeptidase (arylamidase) activity in rat brain.

Changes in the activities of Leu- and Arg-arylamidase in rat frontal and parietal cortices and the subcortical area (including thalamus, hypothalamus, and striatum) were examined in the 2nd, 4th, 8th, 12th, and 24th weeks of life. Average levels found in the subcortical region were greater than those in the cortical areas. The most marked changes in enzymatic activity in the course of brain development were found in the subcortical structure. Leu-arylamidase activity increased from the 2nd week up to the 8th week, returning to the 2nd week level at the 12th and 24th weeks. The maximum levels of Arg-arylamidase activity were found at the 4th and 8th weeks. These data suggest that proteolytic activity is involved in the postnatal development of rat brain.