Synthesis and secretion of insulin-like growth factor (IGF)-II and IGF binding protein-2 by cultivated brain meningeal cells. 
The meninges (the pia mater and the arachnoid) covering the surface of brain parenchyma are known to participate in the regulation of blood circulation and the blood-cerebrospinal fluid barrier.  In the present study, we isolated and characterized some of the major proteins secreted into the conditioned medium of the meningeal cell cultures prepared from 1-2-day-old rats.  Five protein molecules (7 kDa, 16 kDa, 18 kDa, 27 kDa and 32 kDa) were recognized as major proteins in the conditioned medium by SDS-PAGE.  The major proteins were isolated and purified to homogeneity, respectively.  Their N-terminal sequences, except that of 27 kDa protein, were successfully determined.  Homology search has revealed that the N-terminal sequences of the 7 kDa protein and the 32 kDa protein were identical with those of insulin-like growth factor-II (IGF-II) and IGF-binding protein-2 (IGFBP-2), respectively.  The N-terminal sequences of the 16 kDa and 18 kDa molecules were identical with those of the corresponding fragments of IGFBP-2.  The present study demonstrates that cultured meningeal cells produce and secrete large amounts of IGF-II and IGFBP-2.  The meninges may, therefore, be one of the main sources of these proteins in the cerebrospinal fluid and involved in the modulation of neuronal and/or glial cell survival or functioning.