Growth-stimulating effect of kallikrein on rat neural stem cells--II. Immunocytochemical analysis and specificity of the enzyme for neural stem cells.

In a previous paper we reported a new function of tissue kallikrein: rat urinary kallikrein (RUK) has a marked growth-stimulatory effect on neural stem cells prepared from brains of prenatal rats. We here report that conspicuous differentiation of neural stem cells to neurons and/or glial cells did not occur during stimulation by kallikrein, and this growth-stimulating effect of kallikrein is considerably specific for neural stem cells, i.e.

[Growth-stimulating effect of kallikrein on rat neural stem cells].

Tissue kallikrein is expressed in many species and is widely distributed throughout the body, including the brain. In general, this protease is well known to release the vasoactive peptide, kinin, from kininogen. We report here that kallikrein has a prominent growth-stimulating effect on neural stem cells prepared from the brains of prenatal rats.

Actions of insulin-like growth factor binding protein-5 (IGFBP-5) are potentially regulated by tissue kallikrein in rat brains.

Tissue kallikrein (EC 3.4.21.

Expression of tissue kallikrein mRNA in developing rat brains.

Immunoreactive kallikrein has been demonstrated in the neurons of both prenatal and adult rat brains. However, the preferential site is quite different between the prenatal and adult brains, i.e.

Biochemical and immunohistochemical demonstration of tissue kallikrein in the neuronal nuclei of the developing rat brains.

Kallikrein content and cellular localization in the prenatal, newborn and adult rat brains were determined by the enzyme-linked immunosorbent assay and immunohistochemistry. The content was the highest in the prenatal rats and highly predominant in the neuronal nuclei during the prenatal to newborn periods, whereas the immunoreactive kallikrein was mainly located around neuronal cell bodies and their processes in the adult rats. The preferential nuclear localization in the prenatal rat brains was further confirmed by the immunoblotting technique after the SDS-polyacrylamide gel electrophoresis of the lysate of the nuclei fractionated from the prenatal rat brains.