Effect of the miR-21 inhibitor on inflammatory factors in H9c2 cells subjected to H/R injury in the presence or absence of Sal. H9c2 cells were transfected with either a miR-21 inhibitor or inhibitor-NC. Following transfection, cells were pretreated with Sal, and were subsequently maintained under hypoxia for 6 h, followed by 12 h of reoxygenation. mRNA expression levels of (A) IL-6, (B) IL-1β and (C) TNF-α were determined using RT-qPCR and normalized to GAPDH. The levels of (D) IL-6, (E) IL-1β and (F) TNF-α in the culture supernatant were detected by western blot analysis. Data are presented as the mean ± standard deviation of three experiments. *P<0.05 and **P<0.01 vs. the control group; #P<0.05 and ##P<0.01 vs. the H/R group; &P<0.05 and &&P<0.01 vs. the Sal + H/R control group. H/R, hypoxia/reoxygenation; miR-21, microRNA-21; IL, interleukin; TNF-α, tumor necrosis factor-α; NC, negative control; Sal, salidroside.