EFFECT OF GLUTAMINE ON HEAT-SHOCK-INDUCED MESSENGER-RNA AND STRESS PROTEINS

Our aim was to delineate the effect of glutamine on the level of heat shock-inducible mRNA and synthesis of stress protein(s) in cultured ki dney cells. Experiments were carried out using opossum kidney (OK) cel ls. The induction of HSP70 mRNA as well as the synthesis of 72,73 kDa stress proteins was evaluated in cell monolayers exposed to 45-degrees -C for 15 minutes followed by a recovery period at 37-degrees-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 perfor med in the presence of glutamine metabolites, such as NH4Cl, glutamate , or aspartate. Glutamine without preincubation at 37-degrees-C remark ably increased the steady-state level of HSP70 mRNA as well as the pro duction of 72,73 kDa stress proteins in a dose-dependent manner. The p roduction of stress protein(s) in the presence of glutamine was associ ated with decreased percent LDH efflux, suggesting cytoprotective acti on of glutamine in cultured kidney cells. However, when OK cells were preincubated for 1 hour at 37-degrees-C with 10 mM glutamine, there wa s an approximately fourfold decline in level of HSP70 mRNA compared wi th experiments in the presence of 10 mM glutamine without preincubatio n. In addition, metabolites of glutamine, i.e., ammonia and glutamate decreased the level of heat-inducible HSP70 mRNA. Furthermore, asparta te or NH4Cl had little effect on LDH release compared with heat shock experiments, without addition of amino acids. These observations sugge st that metabolites of glutamine may blunt the steady-state level of g lutamate or HSP70 mRNA. The decreased level of HSP70 mRNA in the prese nce of NH4Cl may explain the role of ammonia in renal injury and brain toxicity, as well as glutamate excitotoxicity. (C) 1993 Wiley-Liss, I nc.