The effects of ammonia and glutamine on mitochondrial respiration of rat pancreatic acinar cells

Abstract

During glutamine catabolism is produced ammonia, which can be toxic to cells. In hepatic encephalopathy neuron mitochondria ammonia causes the formation of free radicals, the opening of the mitochondrial permeability transition pore, oxidative phosphorylation disruption and swelling. It is still unknown whether the utilization of glutamine in the mitochondria of acinar cells of the pancreas produces toxic concentrations of ammonia. The experiments were performed on male Wistar rats weighing 250–300 g. Pancreatic acini were isolated using collagenase. Cells were incubated for 30 min with glucose (10 mM) in the control and additionally NH4Cl (5 mM) or glutamine (2 mM) in the experiment. Acetylcholine (10 μM) or cholecystokinin (0.1 nM) was used to stimulate secretion. Respiration rate of isolated rat pancreatic acini was measured using a Clark electrode. Maximum respiration rate was stimulated by addition to the FCCP. Statistical significance (P) of difference between the groups was determined with two-way repeated-measures ANOVA followed by a Holm-Bonferroni corrected post-hoc t tests. The secretagogues acetylcholine and cholecystokinin did not affect basal and FCCP-stimulated respiratory rate. The basal respiratory rate of pancreatic acinar cells decreased with NH4Cl compared to the basal respiratory rate with glucose oxidation, and this decrease was observed both at normal condition and under the action of secretagogues. Glutamine did not affect basal respiratory rate. During glutamine oxidation, the maximum respiratory rate increased compared to the control, regardless of the effect of acetylcholine or cholecystokinin. NH4Cl reduced the maximum rate of FCCP-stimulated respiration in rest or upon stimulation with secretagogues compared to glucose control. Therefore, NH4Cl causes a negative effect mitochondrial respiration regardless of secretory stimulation with acetylcholine or cholecystokinin. The toxic amount of ammonia required for inhibition of mitochondrial respiration is apparently not formed due to glutamine oxidation even when stimulated by acinar cells by secretagogues.