Cell permeable calcium sensitive flouresecent dye. Binds to Ca2+ (Kd = 0.25 µM). Ratiometric and excited by UV light. Hydrolysed into Indo-1 by cytoplasmic esterases. May be used for monitoring Ca<2+> levels. Inhibits renal proximal tubule cell volume regulation. For optimal cell loading, we recommend using with F-127, available either as a 10% solution in water (HB16503) or 20% solution in DMSO (HB9631).