Effect of inhibitors of oxidative phosphorylation on erythropoietin mRNA in isolated perfused rat kidneys
Tan CC., Ratcliffe PJ.
We have used RNase protection to measure oxygen-dependent changes in erythropoietin (EPO) mRNA in isolated perfused kidneys and to compare the effect of hypoxia with the response to inhibitors of oxidative phosphorylation. In well-oxygenated kidneys perfused for 2 h at 12 ml/min, with hematocrit of 0.09 ± 0.005 and PO 2 of 443 ± 67 mmHg, EPO mRNA levels were similar to the baseline levels measured in nonperfused contralateral kidneys from the same animals. When perfusions were performed under identical conditions but at a PO 2 of 32 ± 4 mmHg, EPO mRNA increased ~16-fold. In contrast, graded concentrations of cyanide (10, 100, and 300 μM and 1 mM), antimycin (0.01, 0.1, 0.5, and 1 μM), and oligomycin (0.01, 0.1, and 1 μM) did not alter EPO mRNA in well-oxygenated perfused kidneys. However, in kidneys perfused at low PO 2 with a high concentration of each inhibitor, EPO mRNA levels were increased, demonstrating that the ability to respond to hypoxia was retained. Thus inhibitors of oxidative phosphorylation did not mimic the effects of hypoxia, indicating that oxygen-dependent expression of the EPO gene in the kidney is not effected through hypoxic compromise of oxidative phosphorylation.