Immunohistochemical demonstration of tissue kallikrein in the neurons of rat brain.

The distribution of tissue kallikrein (EC.3.4.21.35) in the rat brain was investigated by an enzyme-linked immunosorbent assay (ELISA) and immunohistochemical technique using antiserum against rat urinary kallikrein. More than 75% of the total amount of kallikrein in the extracts of the cerebral cortex and brain stem was determined by the ELISA to be in the form of prokallikrein, suggesting that the greater part of the enzyme exists in the form of pro-enzyme in the central nervous system. Furthermore, immunohistochemical examination revealed that, although the kallikrein-positive cells were widespread and scattered in the brain, the immunoreactive substances preferentially locate in the neuronal cell bodies and their processes in both the cerebral cortex and brainstem.