Figure 5. L-Phenylalanine potentiates [Ca²⁺]_o-induced IP₁ accumulation.

IP₁ accumulation was measured using the IP-One ELISA Kit as detailed in Methods. Left: Changes in IP₁ accumulation were measured in response to incubation with 0, 1.0, 2.0, 3.0, 5.0 and 7.5 mM [Ca²⁺]_o in HEK293 cells transfected with WT CaSR, or with mutants L173F or P221L. For mutant L173P, IP₁ accumulation was measured in response to 0, 3.0, 5.0, 7.5, 10.0, 15.0, 20.0 and 25.0 mM [Ca²⁺]_o; for mutant P221Q, the IP₁ responses at 0, 3.0, 5.0, 7.5, 10.0, 15.0 mM [Ca²⁺]_o were recorded. The IP₁ response-calcium concentration responses were fitted using Hill equation as described in Methods.