HIF-1α activation and apoptotic gene expression were observed after severe hypoxia in HK-2 cells, with simultaneous miR-210 upregulation. HK-2 cells were cultured in normoxia (21% O2) or hypoxia (0.3% O2) and harvested at 12 h, 24 h and 48 h. (A) mRNA analysis and (B) protein analysis of HIF-1α pathway genes (HIF-1α, GLUT-1, BNIP3 and NIX), HIF-2α and the apoptosis-associated genes p53 and FAS. (C) Optical density quantitative analysis of Western blots in (B). (D) Real-time PCR analysis of miR-210 levels in HK-2 cells. (E) Real-time PCR analysis of miR-210 levels in HK-2 cell medium. All mRNA expression levels were normalized to β-actin (n = 3). Cellular miR-210 levels were normalized to RNU6 (n = 3), and extracellular miR-210 levels were normalized to miR-39 (n = 3). The Western blotting relative expressions are compared with β-actin (n = 3). Data are shown as mean ± SD. *P < 0.05; **P < 0.01; ***P < 0.001.