RESUMO
AIM: To investigate the effects of lipopolysaccharides (LPS, endotoxin) on the calcium content in pancreatic acinar cells and the origin of Ca2+ during calcium overload induced by LPS, further to explore the mechanism of LPS in inducing calcium overload and pancreatic acinar cell injury. METHODS: Male rat pancreatic acinar cells were isolated by collagenase digestion and loaded with Fluo-3/AM, then exposed to varying doses of LPS (from 1 mg/L to 20 mg/L). The dynamic change of [Ca2+]i in single pancreatic acinar cell in the absence and presence of Ca2+ in extracellular fluid was determined by laser scanning confocal microscopy. Cell viability was determined by MTT at different time points after treatment with LPS. RESULTS: Under physiological calcium concentration in extracellular fluid, LPS (10 mg/L) initiated a rapid, concentration-dependent rise in intracellular [Ca2+]i and consequent cell damage (P<0.05). LPS induced a slight rise of [Ca2+]i in the calcium-free extracellular fluid containing egtazic acid 1 mmol/L and addition of extracellular calcium in the presence of LPS resulted in a more immediate and remarkable rise of [Ca2+]i, which reached the peak value within 150 s and maintained the value sustainedly. Egtazic acid attenuated LPS-induced cell damage (P<0.05). The increase in intracellular [Ca2+]i preceded the pathological alteration of pancreatic acinar cells. CONCLUSION: LPS directly induced the injury and the disorder of calcium homeostasis in isolated rat pancreatic acinar cell. Calcium overload is an early event in the pathogenesis of LPS-induced cell damage. Origin of the [Ca2+]i in cytoplasma of pancreatic acinar cells during calcium overload is mainly due to the influx of extracellular Ca2+. Calcium homeostasis disorder may be one of the causes or at least an important mediator of LPS-induced pancreatic acinar cell damage.
