Intracellular calibration of the fluorescent calcium indicator Fura-2

Abstract

We present the techniques we have used and the problems we have encountered in our laboratories in the in vivo calibration of the fluorescent Ca2+-indicator Fura-2. These techniques include the use of potentiometric methods for the precise control and determination of Ca2+ levels in bathing solutions, in association with methods for the equilibration of internal and external solutions with lonophores (Br-A23187, lonomycin, monensin and nigericin). A by-product of these techniques has been the development of a simple procedure that utilizes Fura-2 as a general indicator of lonized Ca2+ concentrations within the physiological range (pCa 7.5 to 5.5), in other experimental solutions. The major a..