Fig. 4.

Effects of short-chain fatty acids (SCFAs; acetate, propionate, or butyrate) on intracellular Ca²⁺ concentration ([Ca²⁺]_i) in human airway smooth muscle (HASM) cells. A: representative traces of fluorescence intensity [change in fluorescence (ΔF) from baseline fluorescence (Fo)] illustrating the characteristics of acetate (i; 10 mM), propionate (ii; 10 mM), or butyrate (iii; 10 mM)-induced [Ca²⁺]_i increases in HASM cells. B: effects of acetate (10 mM), propionate (10 mM), butyrate (10 mM), acetylcholine (1 µM; positive control), or vehicle (H₂O) on transient (initial) [Ca²⁺]_i increases in HASM cells. Data are means ± SE presented as ΔF/Fo. Number of experiments is shown in parentheses. C: effect of pertussis toxin (PTX) (i; 100 ng/mL, for 4-h pretreatment, n = 11), gallein (ii; 10 µM, for 30 min pretreatment, n = 7), U73122 (iii; 5 µM, for 30 min pretreatment, n = 9), or xestospongin C (XeC) (iv; 20 µM, for 30 min pretreatment, n = 9) on propionate (10 mM)-induced transient [Ca²⁺]_i increases in HASM cells. Data represent means ± SE. *P < 0.05, **P < 0.01, and ***P < 0.001 compared with propionate alone.