ARGININOSUCCINATE SYNTHETASE - LOCALIZATION IN ASTROCYTES AND ROLE INTHE PRODUCTION OF GLIAL NITRIC-OXIDE

An antiserum raised against the peptide representing the partial seque nce 196-222 of mouse liver argininosuccinate synthetase (ASS) was used to detect and localize the enzyme in cells of neural primary cultures . No ASS immunoreactivity was detected by Western blotting in homogena tes of mouse pure astroglial cultures and rat astroglia-rich cultures. However, when the cultures had been treated with bacterial lipopolysa ccharide, interferon-gamma, or a combination of both, ASS immunoreacti vity was disclosed. Immunocytochemical examination of rat astroglia-ri ch cultures revealed a colocalization of ASS with the astroglial marke r glial fibrillary acidic protein (GFAP) in many cells. However, there were some GFAP-positive cells showing no specific staining for ASS, a nd vice versa. Colocalization of ASS with the inducible isoform of nit ric oxide synthase in the same cell was shown only occasionally; nitri c oxide synthase was predominantly expressed in microglial cells. In r at neuron-rich primary cultures astroglial cells as well as neurons ex pressed ASS. Cells of mouse pure astroglial cultures were able to synt hesize arginine and, consequently, nitric oxide from citrulline, but n ot from ornithine. The findings demonstrate that ASS is expressed in a stroglial cells under conditions that stimulate long-lasting productio n of nitric oxide; a functional role of this enzyme in the latter proc ess is implicated. GLIA 24:428-436, 1998. (C) 1998 Wiley-Liss, Inc.