Our aim was to delineate the effect of glutamine on the level of heat shockinducible mRNA and synthesis of stress protein(s) in cultured kidney cells. Experiments were carried out using opossum kidney (OK) cells. The induction of HSP70 mRNA as well as the synthesis of 72,73 kDa stress proteins was evaluated in cell monolayers exposed to 45Β°C for 15 minutes followed by a recovery period at 37Β°C for 3 hours. Incubations were performed in Krebs buffer supplemented with 0, 2, 5 , or 10 mM glutamine. A separate series of experiments was performed in the presence of glutamine metabolites, such as NH,CI, glutamate, or aspartate. Glutamine without preincubation at 37Β°C remarkably increased the steady-state level of HSP70 mRNA as well as the production of 72,73 kDa stress proteins in a dose-dependent manner. The production of stress protein(s) in the presence of glutamine was associated with decreased percent LDH efflux, suggesting cytoprotective action of glutamine in cultured kidney cells. However, when OK cells were preincubated for 1 hour at 37Β°C with 10 mM glutamine, there was an approximately fourfold decline in level of HSP70 mRNA compared with experiments in the presence of 10 mM glutamine without preincubation. In addition, metabolites of glutamine, i.e., ammonia and glutamate decreased the level of heat-inducible HSP70 mRNA. Furthermore, aspartate or NH,CI had little effect on LDH release compared with heat shock experiments, without addition of amino acids. These observations suggest that metabolites of glutamine may blunt the steady-state level of glutamate or HSP70 mRNA. The decreased level of HSP70 mRNA in the presence of NH,CI may explain the role of ammonia in renal injury and brain toxicity, as well as glutamate excitotoxicity. o 1993 Wiley-Liss, Inc.
Glutamine, one of the most abundant amino acids in many organs (Kovacevic and McGivan, 19831, has a central role in metabolic processes (Engstrom and Zetterberg, 1984;Welbourne, 1987), including energy metabolism (Zielke et al., 1984), brain nitrogen metabolism and ammonia detoxification (Yudkoff et al., 1988,