Metabolism of oestradiol-17beta by intestinal bacteria in rats.

In vitro experiments were carried out in which [4-14C]oestradiol-17beta was incubated with a culture from caecal content from adult male rats at 37 degrees C in an atmosphere of nitrogen. Oestrone was identified as the only certain metabolite. Other metabolites, if present, were quantitatively unimportant. The conversion of oestradiol-17beta to oestrone was estimated to be 22-42%.