Kallikrein-kinins in the central nervous system

We studied whether the components of the kallikrein-kinin system are present in the central nervous system. We found that human cerebrospinal fluid (CSF) contains free kinins: 53 +/- 15 pg/ml; kininogen: 10.9 +/- 2.1 ng kinin equivalent/ml, and kininogenase activity: 5.0 +/- 2.1 ng kinins/ml/minute. Kininogenase activity was 2-3 fold augmented by preincubation with trypsin. Soybean trypsin inhibitor completely inhibited untreated CSF and partially inhibited trypsin activated kininogenase. Kininogenase activity and immunoreactive glandular kallikrein were present in rat brain, and their concentrations in hypothalamus is several-fold higher than in cortex, pons-medulla, basal ganglia and cerebellum. In the hypophysis, activity in pars-intermedia was between 6- and 20-fold higher than in posterior and anterior hypophysis, respectively. High activity was also found in the pineal gland. The kallikrein-kinin system is present in the central nervous system where it may participate in modulation of nervous and neuroendocrine functions.