calcimycin and ferric-chloride

The present study evaluates the effect of free radicals generated by xanthine oxidase-catalyzed oxidation of hypoxanthine on cellular function of isolated rat pancreatic acinar cells. The results show that a rapid and sustained increase in intracellular Ca2+ concentration ([Ca2+]i) preceded all other morphological and functional alterations investigated. Radical-induced [Ca2+]i increase was largely inhibited by 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester, which prevents Ca2+ release from intracellular stores, but not by Ca2(+)-depleted medium. Radicals released Ca2+ from thapsigargin-insensitive, ryanodine-sensitive intracellular stores, whereas the secretagogue caerulein at physiological concentrations mainly released Ca2+ from thapsigargin-sensitive stores. In contrast to effects of the secretagogue, radical-induced Ca2+ changes did not cause luminal protein secretion but cell death. In single-cell measurements, both secretagogue and radicals induced oscillations of [Ca2+]i. Radical-induced oscillations had a lower frequency but similar amplitude when compared with caerulein-induced oscillations. 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid and ryanodine, which prevented the radical-induced Ca2+ increase without altering the generation of radicals, markedly reduced the radical-induced cell damage. These results suggest that the Ca2+ increase mediates the radical-induced cell injury. The studies also indicate that not only the extent and duration but also the origin of [Ca2+]i release as well as the frequency of Ca2+ oscillations may determine whether a pancreatic acinar cell will secrete or die.

Topics: Adenosine Triphosphate; Amylases; Animals; Calcimycin; Calcium; Cells, Cultured; Ceruletide; Chlorides; Cytosol; Edetic Acid; Ferric Compounds; Free Radicals; Hypoxanthine; Kinetics; L-Lactate Dehydrogenase; Male; Oxidative Stress; Pancreas; Rats; Rats, Wistar; Ryanodine; Thapsigargin; Xanthine Oxidase

Lipid peroxidation induced in isolated rat hepatocytes by FeCl3 (0.1 mM) was associated with an increase in the cytosolic free Ca2+ and in the ionophore-mobilizable Ca2+ content of both mitochondrial and extramitochondrial (endoplasmic reticular) pools. Ca2+ accumulation was completely prevented by the antioxidants promethazine and vitamin E succinate and was not linked to the inhibition of plasma membrane (Ca2+ + Mg2+)-ATPase and Ca2+ transport or to the depletion of intracellular ATP content. Moreover, preincubation of the hepatocytes with the Ca2+ channel blockers verapamil and nifedipine inhibited the elevation of cytosolic Ca2+, as well as the ion accumulation without interfering with the stimulation of lipid peroxidation by iron. These results suggest that peroxidative alterations of the hepatocyte plasma membranes might perturb the functions of verapamil- and nifedipine-sensitive Ca2+ channels resulting in a net influx of Ca2+, which is subsequently sequestrated in the intracellular compartments.

Topics: Animals; Calcimycin; Calcium; Carbonyl Cyanide m-Chlorophenyl Hydrazone; Cell Membrane; Cells, Cultured; Chlorides; Cytosol; Digitonin; Endoplasmic Reticulum; Ferric Compounds; Kinetics; Lipid Peroxidation; Liver; Male; Membrane Potentials; Mitochondria, Liver; Promethazine; Rats; Rats, Inbred Strains; Tocopherols; Vanadates; Vitamin E