When added to cells, Fura-2AM crosses cell membranes and once inside the cell, the acetoxymethyl groups are removed by cellular esterases. Removal of the acetoxymethyl esters regenerates "Fura-2", the pentacarboxylate calcium indicator.
When added to cells, Fura-2AM enters cells and is converted into Fura-2 after being processed by cellular esterases.