FIGURE 2.

Development of a DMR assay for the human sweet taste receptor. (A) Application of increasing concentrations of sucralose onto R2/R3 U2OS cells cause a positive DMR signal. Arrow indicates time of application. (B) Application of increasing concentrations of sucralose onto parental U2OS cells does not cause a comparable positive DMR signal. Arrow indicates time of application. (C) Kinetics of sucralose (1 mM)-induced DMR responses over a period of 3 months. 19 independent experiments were conducted during that period. In 2 of these experiments (red traces) the DMR responses returned to background levels while in the remaining experiments they stayed above background levels. Arrows indicate time of application. (D) Determination of assay window robustness at the peak or final DMR responses. A maximum concentration of sucralose (1 mM) was used to stimulate either R2/R3 U2OS cells or parental U2OS cells (number of independent experiments are indicated on the bar graph). Peak and final DMR responses were recorded and averaged. Data shows that measurement at the peak response provides a better assay window (unpaired, t-test, α = .05). (E) Representative sucralose dose-response analysis on R2/R3 U2OS cells and parental U2OS cells. Dose-response is representative of several independent experiments and each data point corresponds to an average and standard deviation of a triplicate determination. Averaged potency value for sucralose is summarized in Table 1.