Identification ofGlucocorticoid-inducible Cytochromes P-450 intheIntestinal MucosaofRatsandMan

We usedmonoclonal antibodies andcomplementary DNAs (cDNAs) toglucocorticoid-inducible liver cytochromes P450 inrats(P450p) andinman (HLp)tosearch forrelated cytochromes inintestinal mucosa.Inratenterocytes, we found twodexamethasone-inducible proteins related tothesteroidinducible liver cytochromes P450.Induction ofthese proteins inenterocytes wasassociated withincreases intheamountofa P450p-related messengerRNA andoferythromycin demethylase, an activity highly characteristic ofP450pandHLp. Similar studies on humanjejunal enterocytes revealed a microsomal protein indistinguishable fromHLponimmunoblots andan abundance ofRNA hybridizing withHLpcDNA.In humanenterocytes thespecific concentration oftheHLp-related cytochrome (measured immunochemically oraserythromycindemethylase activity) was similar tothatfoundin humanliver andcould account foralloftheCO-binding hemoprotein detected. We conclude thattheintestinal mucosacontains prominent form(s) ofcytochromes P450similar toliver cytochrome P450pintheir structure, function, andsomeregulatory characteristics.