Figure 4. L-Phe modulates the [Ca²⁺]_o concentration response curves in CaSR-transfected HEK293 cells.

The [Ca²⁺]_i responses of HEK293 cells transiently overexpressing WT CaSR or disease-related mutations were measured using Fura-2AM during stepwise increases in [Ca²⁺]_o from 0.5 to 30 mM with or without L-Phe as above. The ratio of light emitted at 510 nm upon excitation alternately with 340 or 380 nm was normalized to the maximum response. And the average [Ca²⁺]_i responses at various [Ca²⁺]_o were normalized and plotted against [Ca²⁺]_o and further fitted using the Hill equation. Open marker: in the absence of L-Phe; Closed marker: in the presence of 5 mM L-Phe.