title: Silica increases cytosolic free calcium ion concentration of alveolar macrophages in vitro.
abstract: Rat alveolar macrophages were exposed to silica dust (quartz) suspended in culture medium (SiO2, dry particle size less than 5 microns in diameter) and fluctuation in their cytosolic free calcium content ([Ca2+]i) was detected in cell monolayers with a fluorescent calcium probe (Indo-1AM). Cytosolic free calcium content was correlated with lactate dehydrogenase (LDH) release, an index of cell damage. SiO2 induced a concentration- and time-dependent increase of cytosolic free Ca2+ ion concentration and LDH release. [Ca2+]i was increased about fivefold when cells were exposed to 200 micrograms of SiO2 per milliliter (3 ml per dish) for 2 hr. [Ca2+]i changed within 15 min of SiO2 treatment, whereas LDH release was measurably increased only after 30 min. Chelation of extracellular Ca2+ by 2 mM ethylene glycol bis(beta-aminoethyl ether) N,N'-tetraacetate did not prevent SiO2-induced fluctuation of macrophage [Ca2+]i, but did partially prevent the SiO2-induced increase in LDH release (p less than 0.01). We conclude that a very early event in SiO2-induced damage of alveolar macrophages involves mobilization of intracellular calcium pools to increase [Ca2+]i. These results suggest that SiO2-induced macrophage damage, a key event in the development of silicosis, may involve perturbation of intracellular calcium homeostasis.
authors.affiliation: Department of Occupational Medicine, School of Public Health, Beijing Medical University, People's Republic of China.
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.forename: L C
authors.initials: LC
authors.lastname: Armstrong
authors.forename: S J
authors.initials: SJ
authors.lastname: Liu
authors.forename: J E
authors.initials: JE
authors.lastname: Gerriets
authors.forename: J A
authors.initials: JA
authors.lastname: Last
mesh_terms: D000818:Animals; D002118:Calcium / Q000032:analysis*; D002478:Cells, Cultured; D003600:Cytosol / Q000737:chemistry; D005110:Extracellular Space / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D006706:Homeostasis / Q000187:drug effects; D007211:Indoles; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008262:Macrophage Activation / Q000187:drug effects / Q000502:physiology; D016676:Macrophages, Alveolar / Q000737:chemistry / Q000187:drug effects / Q000648:ultrastructure*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012822:Silicon Dioxide / Q000009:adverse effects / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D005456:Fluorescent Dyes; D007211:Indoles; C059587:Indo-1 pentaacetoxymethyl ester; D012822:Silicon Dioxide; D007770:L-Lactate Dehydrogenase; D002118:Calcium