title: Effects of calcium on intestinal mucin: implications for cystic fibrosis.
abstract: A major feature of the disease cystic fibrosis is the excessive concentration of mucus within ducts and glands of mucous-producing organs. Some mucous secretions also show an elevation in calcium concentration. Using purified rat intestinal goblet cell mucin as a model mucin, we have investigated the effect of millimolar additions (1-25 mM) of CaCl2 on the physical properties of the mucin. Isotonicity of incubation media was preserved in order to mimic in vivo conditions. CaCl2 (8-15mM) caused a 15-33% decrease in viscosity, no change in electrophoretic mobility in acrylamide gels, and a 20-30% decrease in solubility of the mucin. Solubility changes were reversed by the addition of EDTA (20 mM) to incubations. Insolubility was also produced in incubations of mucin with a mixture of soluble intestinal contents (NaCl washings). These findings strongly suggest that the mucin became smaller and more dense as calcium was added, a process most probably achieved by loss of intramolecular water.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D003550:Cystic Fibrosis / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D007419:Intestinal Secretions / Q000187:drug effects*; D009077:Mucins / Q000378:metabolism*; D051381:Rats; D012995:Solubility; D014461:Ultracentrifugation; D014783:Viscosity
chemical_list: D009077:Mucins; D002118:Calcium