Fig. 2.

A: effect of extracellular Ca²⁺ concentration ([Ca²⁺]_e) on increase of [Ca²⁺]_i in STC-1 cells in the absence or in the presence of l-proline. Each data point represents a separate assay, where the cells were placed into a cuvette in Ca²⁺-free HBSS, and then Ca²⁺ was added to reach the final concentration shown in the abscissa. Increase in [Ca²⁺]_i is plotted against final [Ca²⁺]_e. Top trace was obtained from 2 experiments, where Ca²⁺-containing solution was added in the presence of 5 mM l-proline. The bottom trace, also from 2 experiments, was in the absence of l-proline. B: effect of increasing concentrations of l-proline on [Ca²⁺]_i in the presence of [Ca²⁺]_e at either 0.1 or 1.8 mM. The top trace is derived from 2 separate experiments with [Ca²⁺]_e of 1.8 mM. The bottom curve is derived from 3 separate experiments with [Ca²⁺]_e at 0.1 mM.