title: Ratiometric measurement of intracellular pH of cultured cells with BCECF in a fluorescence multi-well plate reader.
abstract: A number of methods have been developed to measure intracellular pH (pHi) because of its importance in intracellular events. A major advance in accurate pHi measurement was the development of the ratiometric fluorescent indicator dye, 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein (BCECF). We have used a fluorescence multi-well plate reader and a ratiometric method for determining pHi in primary cultures of rabbit corneal epithelial (CE) cells with BCECF. Fluorescence was measured at excitation wavelengths of 485 +/- 11 nm and 395 +/- 12.5 nm, with emission detected at 530 +/- 15 nm. Cells grown in multi-well plates were loaded with 4 microM BCECF for 30 min at 37 degrees C. Resting pHi was 7.34 +/- 0.03 (2 cultures, N = 5 wells). Changes in pHi determined with the fluorescence multi-well plate reader after the addition and removal of NH4Cl or sodium lactate were comparable to changes in cells analyzed with a digitized fluorescence imaging system. A concentration-response relationship involving changes in pHi was easily demonstrated in CE cells after treatment with ionomycin, a calcium ionopore. Low doses of ionomycin (2.5-5 microM), produced a prolonged acidification; 7.5 microM ionomycin produced a transient acidification; and 10 microM ionomycin resulted in a slight alkalinization. We conclude that accurate pHi measurements can be obtained with a ratiometric method with BCECF in a multi-well plate reader. This technology may simplify screening studies evaluating effects of hormones, growth factors, or toxicants on pHi homeostasis.
authors.affiliation: Division of Pharmacology & Toxicology, College of Pharmacy, University of Texas at Austin 78712-1074, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: Grant
authors.forename: D
authors.initials: D
authors.lastname: Acosta
mesh_terms: D000643:Ammonium Chloride; D000818:Animals; D002021:Buffers; D002478:Cells, Cultured; D003315:Cornea / Q000166:cytology; D004848:Epithelium; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D015759:Ionomycin; D007476:Ionophores; D008985:Monensin; D009550:Nigericin; D011817:Rabbits; D019354:Sodium Lactate; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: D002021:Buffers; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007476:Ionophores; D000643:Ammonium Chloride; D015759:Ionomycin; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D008985:Monensin; D009550:Nigericin; D019354:Sodium Lactate