title: Osteoblastic intracellular pH and calcium in metabolic and respiratory acidosis.
abstract: In vitro metabolic acidosis (Met) induces greater bone mineral resorption than respiratory acidosis (Resp). Met, but not Resp, inhibits osteoblasts which control many aspects of osteoclastic function. To determine whether at a similar decrement in extracellular pH, Met and Resp would induce different changes in intracellular pH (pHi) and/or intracellular calcium concentration ([Ca2+]i) of osteoblasts, we measured pHi and [Ca2+]i in an osteoblast-like rat osteosarcoma cell line (UMR-106). Cells were grown to confluence on glass slides and loaded with either 1.5 microM BCECF, for pHi, or 1.5 microM Fura-2, for [Ca2+]i, in control (Ctl; pH approximately 7.40, PCo2 approximately 40, [HCO3-] approximately 24) medium. The fluorescence ratio at excitation wavelengths of 502 and 440 nm was measured for pHi and at 340 and 380 nm for [Ca2+]i. Following a baseline scan in Ctl medium, cells were transferred to either Met (pH approximately 7.10, PCo2 approximately 40, [HCO3-] approximately 12), Resp (pH approximately 7.10, PCo2 approximately 80, [HCO3-] approximately 24) or Ctl conditions. Medium pH, PCo2 and [HCO3-] were held constant over the course of the experiment. Compared to Ctl, pHi was lower in Met (P < 0.001) and even lower in Resp (P < 0.001 vs. Met and vs. Ctl). These changes were maintained over the period of observation. Compared to Ctl, [Ca2+]i was higher in Met (P < 0.001) and even higher in Resp (P < 0.001 vs. Met and vs. Ctl) within 20 to 100 seconds. However, after 100 seconds [Ca2+]i was not different in the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, University of Rochester School of Medicine and Dentistry, New York, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Ori
authors.forename: S G
authors.initials: SG
authors.lastname: Lee
authors.forename: N S
authors.initials: NS
authors.lastname: Krieger
authors.forename: D A
authors.initials: DA
authors.lastname: Bushinsky
mesh_terms: D000138:Acidosis / Q000378:metabolism* / Q000473:pathology; D000142:Acidosis, Respiratory / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism*; D010006:Osteoblasts / Q000378:metabolism*; D051381:Rats; D013997:Time Factors
chemical_list: D002118:Calcium