What kinds of positive controls are necessary for calcium assays?

Ionomycin serves as a positive control in experiments to generate the maximum calcium flux ratio. This ionophore has been utilized at concentrations between 10^(-7) to 10^(-5) M and also facilitates the movement of calcium from intracellular stores to the cytosol. Specifically, it enhances the entry of calcium (and manganese) by activating existing cellular pathways designed for this purpose, rather than by transporting these ions across the cell membrane. Another positive control is thapsigargin. It is a compound that inhibits the SERCA pump, a protein responsible for transporting calcium ions into the endoplasmic reticulum (ER). By blocking this pump, thapsigargin induces the depletion of calcium stores within the ER. As a result, there is a moderate increase in cytosolic calcium levels.