Glutamine synthetase in experimental meningitis: increased ratio of the subunits 3 and 2 may indicate enhanced activity

Glutamine synthetase (GS) activity is higher in the neocortex but not in th e hippocampal formation of rabbit brain during Streptococcus pneumoniae men ingitis compared to the respective brain region of uninfected control anima ls. One-dimensional polyacrylamide gel electrophoresis (1D-SDS-PAGE) reveal ed an apparent molecular mass (M-r) of 44 000 Dalton (Da) for GS from rabbi t brain. After two-dimensional gel electrophoresis (2D-PAGE), followed by C oomassie-blue staining, GS separated into three distinct spots (S1, S2, S3) . One additional spot (S4) occurred on the immunoblot. All four GS spots ex hibited the same M-r (44 000 Da), but differed in their isoelectric points. Densitometric evaluation of the two-dimensional maps revealed a strong inc rease of optical density (OD) of S3 in the frontal cortex of infected anima ls. The calculated OD ratio S3/S2 in the frontal cortex from rabbits with m eningitis was 1.75+/-0.68 (mean+/-standard deviation). Compared to controls (0.85+/-0.39), this value was significantly increased (p = 0.0006). In the hippocampal formation, the ratio S3/S2 was nearly unchanged during meningi tis. it is suggested that the ratio S3/S2 may indicate a neuroprotective fe ature of rabbit brain during meningitis since neuronal apoptosis occurs onl y in the dentate gyrus and not in the frontal cortex. (C) 2000 Elsevier Sci ence B.V. All rights reserved.