Figure 1. Two phases of Ca²⁺ signaling in in vitro lacrimal gland preparations.

Top: Changes in intracellular Ca²⁺ in slices of rat lacrimal gland are inferred from the efflux rate of ⁸⁶Rb⁺. Redrawn from data originally presented in [11]. Bottom: Changes in intracellular Ca²⁺ in mouse lacrimal acinar cells are measured with the Ca²⁺ indicator, Fura-2. In both cases, in the absence of extracellular Ca²⁺, the response is transient, and subsequently restored by addition of Ca²⁺.