Summary of the important reactions involved in the control of Ca2+ in a salivary acinar cell. Agonist stimulation induces the formation of IP3, which releases Ca2+ from the endoplasmic reticulum (ER) via the opening of IP3 receptors (IPR). The rate of degradation of IP3 is Ca2+-dependent. Calcium is pumped into the ER, and out of the cell, by ATPase pumps, while it can also leave the ER through ryanodine receptors (RyR). Jpm represents the removal of Ca2+ from the call by plasma membrane ATPase pumps, while Jin represents a generic influx of Ca2+, most likely through receptor-operated or store-operated Ca2+ channels.