Biliary Metabolites of 17β-Estradiol-4-14C in the Bull

After intravenous injection of 17β-estradiol-4-14C into a bull, a plot of the disappearance of radioactivity from blood indicated 2 discrete half-lives of 4.5 and 15 min. Radioactivity in bile, which was collected from the gallbladder by catheter, reached a maximum concentration at 12 min. In 3 hr, 53% of the dose was excreted in bile and 4% in urine. The radioactive metabolites in the bile were not ether-extractable until after hydrolysis in the presence of β-glucuronidase. Two steroid aglycones, estrone-MC and 17α-estradiol-14C, accounted for 94% of the biliary radioactivity of the first half hour. The remaining 6% was more hydrophilic than estriol and was not identified. (Endocrinology 78: 914, 1966)