FIGURE 5.

Induction of [Ca²⁺]_i rise by HYA in Caco-2 cells and HEK293 cells expressing human GPR40. A, mobilization of [Ca²⁺]_i induced by HYA, HYB, and linoleic acid (100 μm each) was monitored in Caco-2 cells, and data are presented as relative Ca²⁺ intensity (n = 3). LA, linoleic acid. **, p < 0.01, and *, p < 0.05, compared with untreated; $$, p < 0.01, compared with HYA (Tukey-Kramer). B, mobilization of [Ca²⁺]_i induced by HYA, HYB, and linoleic acid (10 μm each) was monitored in GPR40-expressing HEK293 cells. The cells were pretreated with or without the GPR40 antagonist GW1100 for 15 min prior to the addition of the fatty acids. HEK293 cells not expressing GPR40 were used as negative controls (doxycycline (Dox (−)) (n = 3).**, p < 0.01, compared with untreated; ##, p < 0.01, compared with GW1100 (+). NS, not significant (Tukey-Kramer). C, representative dose-response curve of HYA-induced [Ca²⁺]_i rise in HEK293-hGPR40 cells (n = 3). ●, linoleic acid; ■, HYA; ▾, HYB. Inactive, no response at 1,000 μm. EC₅₀ indicates the concentration of a sample that produces 50% of the maximal response and was calculated from dose-response curves. Results are expressed as means ± S.E. Each result (A–C) is representative of three similar experiments.