title: Physiological and cytotoxic effects of Ca(2+) ionophores on Caco-2 paracellular permeability: relationship of 45Ca(2+) efflux to 51 Cr release.
abstract: The human intestinal cell line, Caco-2, and the Ca2+ ionophores, A23187 and ionomycin, were used to determine the interrelationships of 45Ca(2+) efflux, transepithelial electrical resistance (Rt), and [3H]-mannitol flux to changes in 51Cr release and lactate dehydrogenase (LDH) activity. Treatment of Caco-2 monolayers with ionomycin at concentrations of between 0.25 and 2.50 mumol/l showed similar 45Ca(2+) efflux rate constants and coefficients. Analysis of the control and ionomycin-induced 45Ca(2+) efflux values showed the data to best fit a three Ca(2+) compartmental model. All changes in Caco-2 Rt and [3H]-mannitol flux were reversible with no significant increases in 51Cr release with ionomycin concentrations of less than or equal to 2.5 mumols/l. Caco-2 monolayers treated with ionomycin at concentrations of between 5.0 and 50.0 mumols/l showed rapid non-exponential 45Ca(2+) effluxes with irreversible changes in Rt, [3H]-mannitol flux, and significant increases in 51Cr release. There was no changes in media LDH activity using either ionomycin or A23187 at concentrations of up to 50 mumols/l for 60 min. The results of our study show that: (1) disruption of Ca(2+) homeostasis in Caco-2 cells will occur with the addition of Ca(2+) ionophores at concentrations of greater than 2.50 mumols/l; (2) high concentrations (greater than 2.5 mumols/l) of ionomycin will cause non-exponential 45Ca(2+) efflux rates with irreversible changes in intracellular Rt and 14C-mannitol flux, and (3) early signs of Ca(2+) ionophore-induced damage can be detected by 51Cr release from Caco-2 cells into the media and not by changes in LDH media activity.
authors.affiliation: Medical Research Service, Veterans Administration Medical Center, St. Louis, Mo.
authors.forename: M J
authors.initials: MJ
authors.lastname: Rutten
authors.forename: J N
authors.initials: JN
authors.lastname: Cogburn
authors.forename: C S
authors.initials: CS
authors.lastname: Schasteen
authors.forename: T
authors.initials: T
authors.lastname: Solomon
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002857:Chromium / Q000378:metabolism*; D002860:Chromium Radioisotopes; D004553:Electric Conductivity; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008353:Mannitol / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D002132:Calcium Radioisotopes; D002860:Chromium Radioisotopes; D002857:Chromium; D000001:Calcimycin; D008353:Mannitol; D015759:Ionomycin; D007770:L-Lactate Dehydrogenase; D002118:Calcium