Age-related alterations in Ca2+ signals and mitochondrial membrane potential in exocrine cells are prevented by melatonin

Information regarding age-induced Ca2+ signal alterations in nonexcitable cells is limited. In addition, little evidence exists on the ability of melatonin to palliate the effects of aging on Ca2+ signals and mitochondrial potential, a parameter involved in both Ca2+ signaling and aging. We studied the ability of melatonin to prevent the effects of aging on intracellular Ca2+ homeostasis and mitochondrial potential in exocrine cells. Pancreatic acinar cells were obtained from adult (3 months old) and aged (22-24 months old) mice by collagenase dispersion. Ca2+ signals, in situ mitochondrial potential and in vitro amylase secretion were determined. Secretion in response to increasing levels of the secretagogues, acetylcholine and cholecystokinin (CCK), were impaired in aged pancreatic acini. This decrease was accompanied by an inhibition in the amplitude of the peak response to maximal concentrations of the agonists, and by a decrease in the pattern of Ca2+ oscillations induced by postprandial levels of CCK. Both the size of the calcium pools, assessed by low levels of ionomycin, and capacitative calcium entry, induced by depletion of the stores with thapsigargin, were diminished in aged cells. These changes in Ca2+ homeostasis were associated with depolarization of intracellular mitochondria. Oral administration of melatonin for 3 months to aged mice restored the secretory response, the amplitude and frequency of Ca2+ responses, the size of intracellular calcium pools, the capacitative calcium entry, and the mitochondrial potential. In conclusion, melatonin restores secretory function, Ca2+ signals and mitochondrial potential of aged exocrine cells.