Acute oxidative stress modulates secretion and repetitive Ca2+ spiking in rat exocrine pancreas

The effects of the oxidant tert-butylhydroperoxide (t-buOOH) on carbachol-s timulated pancreatic secretion in the vascularly perfused rat pancreas have been studied in parallel with [Ca2+](i) signalling and amylase output in p erifused rat pancreatic acinar cells. Perfusion of the pancreas with t-buOO H (0.1-1 mM) caused a rapid and irreversible inhibition of carbachol-stimul ated (3 x 10(-7) M) amylase and fluid secretion. Pre-perfusion of the pancr eas with vitamin C and dithiothreitol or a cocktail of GSH and GSH-precurso r amino acids provided only marginal protection against the deleterious eff ects of t-buOOH, even though GSH levels were elevated significantly. In per ifused pancreatic acini, repetitive [Ca2+](i) spikes evoked by carbachol (3 x 10(-7) M) were sustained for 40 min, t-buOOH (1 mM) acutely increased th e amplitude and duration of Ca2+ spikes, then attenuated Ca2+ spiking and s ubsequently caused a marked and sustained rise in [Ca2+](i). t-buOOH-induce d alterations in carbachol-stimulated [Ca2+](i) signalling and amylase rele ase in perifused pancreatic acini were prevented by vitamin C. Although vit amin C restored impaired Ca2+ signalling and maintained amylase output in p ancreatic acini, it seems likely that oxidative stress inhibits fluid secre tion irreversibly in the intact pancreas, resulting in a loss of amylase ou tput. Thus, perturbations in [Ca2+](i) signalling may not fully explain the secretory block caused by oxidative stress in acute pancreatitis. (C) 1999 Elsevier Science B.V. All rights reserved.