Bilonoha O. Аdaptive capacity of rat pancreatic acinar cells mitochondria upon various functional states

New parameters of adaptive capacity of rat pancreatic acinar cells mitochondria were characterized: maximal uncoupled respiration, optimal protonophore concentration, respiration acceleration and deceleration. These parameters depended on the oxidative substrate and functional states of pancreatic acini. In most cases (except for glutamine oxidation) the acceleration was much higher after 1.5 μM FCCP and maximal peak respiration – after 0.5 μM FCCP. Only when malate or isocitrate was present, deceleration was significantly higher. It has been found that, the increase in the respiration rate was proportional to the decrease in membrane potential. The coefficient of elasticity and the area under the curves of the dependence of respiratory rate on the concentration of FCCP were used for formalize the assessment of adaptive capacity of mitochondria. Elasticity coefficient was the highest when the combination of glucose, glutamine and pyruvate was present and the lowest when monomethyl-succinate was oxidized. The combination of three substrates (glucose, pyruvate and glutamine) maintains the highest respiration rate in response to FCCP load. Upon acetylcholine or cholecystokinin stimulation, maximal uncoupled respiration rate increased only upon the oxidation of pyruvate with glucose; insulin stimulated only when glucose-fueled uncoupled respiration, but abolished the stimulative effect of cholecystokinin on pyruvate-fueled uncoupled respiration. Ethanol in vitro suppressed rate of cholecystokinin-stimulated uncoupled respiration of pancreatic acini, while combination of ethanol with cholecystokinin caused an increase in number of necrotic cells and cells with plasma membrane blebs. These effects were defendant on the oxidative substrates in the medium. Combination of ethanol and CCK in vitro caused the decrease of uncoupled respiration of pancreatic acini only upon the oxidation of glutamine independently of other substrates. Moreover, mitochondrial membrane depolarization and NADH autofluorescence increase caused by CCK and ethanol were not observed upon glutamine supplementation. Combination of ethanol and CCK caused increase necrosis only in case of glucose presence, but not when either pyruvate or glutamine were added. Substantial increase in plasma membrane blebbing was observed only after incubation with combination of glucose, glutamine, pyruvate and combination of ethanol and CCK. After a single in vivo administration of ethanol (2 h), CCK (1 h) or combination thereof, the fraction of necrotic cells and plasma amylase level did not change indicating the lack of pancreatic damage. However, the number of cells with membrane blebbing substantially increased in animal group treated with both ethanol and CCK. Basal respiration rate of isolated pancreatic acini was lower in animals after ethanol administration irrespectively of the oxidative substrate. Neither EtOH nor CCK on their own affected the uncoupled respiration, but their combination caused a significant decrease of the maximal uncoupled respiration. Chronic alcohol administration (14 days) caused an increase of FCCP-stimulated respiration upon glucose oxidation, but not when pyruvate was co-administered for 7 last days. Pyruvate also ameliorated the negative effects of ethanol administration on other mitochondrial parameters: oligomycin-insensitive respiration and IC50 of FCCP on mitochondrial membrane potential. Number of necrotic cells mildly increased in the group of animals after ethanol administration, but no such effect was observed in the group of animals that were also injected with pyruvate. Plasma amylase level in animals after ethanol administration did not increase indicating no full-blown pancreatitis. Thus, the parameters of adaptive mitochondrial capacity are useful tools to study both different aspects of normal pancreatic acinar cells functioning and mechanisms of pathogenesis of pancreatic diseases.