Oxygen-regulated expression of EPO in REPCs. (A) Two established human renal cell lines (HEK 293 and TK173), REPCs, and HepG2 as a positive control were tested for hypoxia (24 hours at 1% O2)–induced expression of EPO. Shown are representative agarose gel electrophoreses stained with ethidium bromide. (B) Time course of EPO mRNA expression measured by real-time PCR and normalized to β-actin after up to 24 hours under conditions of 3% and 1% oxygen. Shown are the means ± SD; n = 6; *P < .05; **P < .01; ***P < .001. (C) Time course of EPO protein secretion after hypoxic stimulation of REPCs as measured by ELISA (R&D Systems). Shown are the means ± SD; n = 4; *P < .05; **P < .01; ***P < .001. (D) Time course of EPO mRNA expression measured by real-time PCR and normalized to β-actin after up to 6 days under 1% oxygen conditions. Shown are the means ± SD; n = 6; *P < .05; **P < .01; ***P < .001.
