Differential inhibition by iodonium compounds of induced erythropoietin expression

Diphenylene iodonium chloride suppresses the cobaltous chloride-induced expression of erythropoietin by Hep3B cells to about 50% at a concentration of 30 nM. At that concentration, it has no effect on the response to low oxygen. The related compound iodonium diphenyl chloride acts similarly but is a much less effective inhibitor. If, as reported, diphenylene iodonium chloride is a specific inhibitor of cytochrome b, it follows that the response to CoCl2 is dependent on that enzyme but the response to hypoxia is not.