Membrane-permeant form of Rhod-590 that can be loaded into cells via incubation. Because of the relatively low water solubility of the AM ester, Pluronic F-127, a mild detergent, is often used as a dispersing agent to facilitate dye loading. Rhod-590 AM ester itself does not bind Ca2 , but it is readily hydrolyzed to Rhod-590 by endogenous esterases once it enters cells.