Fig. 4.

Involvement of FFAR1 and FFAR4 in transient [Ca²⁺]_i increases induced by long-chain free fatty acids (oleic acid or linoleic acid) in HASM cells. A and B: representative gel images of immunoblot analyses of FFAR1 (A) and FFAR4 (B) protein expression in HASM cells that were transfected with either control nontargeting small interfering RNA (siRNA), FFAR1-specific siRNA, or FFAR4-specific siRNA (targeting for both FFAR4 transcript variant 1 and variant 2) 3 days before analysis. GAPDH was used as loading control. These images are representative of at least 3 independent experiments. C and D: representative traces of fluorescence intensity illustrating the oleic acid (10 μM)-induced [Ca²⁺]_i increases in nontransfected HASM cells, HASM cells transfected with nontargeting siRNA control, or HASM cells transfected with either FFAR1 or FFAR4 siRNA. At time 0, oleic acid was injected to the buffer in the wells. E and F: effect of downregulation of FFAR1 (E; n = 5) or FFAR4 (F; n = 8) by siRNA on oleic acid (10 μM)- or linoleic acid (10 μM)-induced transient [Ca²⁺]_i mobilization in HASM cells. *P < 0.05; **P < 0.01 compared with the HASM cells transfected with nontargeting siRNA control.