Abstract
The metabolic fate of diethylstilbestrol (DES) in steers was studied by giving single oral doses of 14C-DES and sacrificing the animals 24, 48, 72, 120, 168 and 240 hr. after dosing (two steers per time interval). Total recovery of 14C averaged 97% of the dose, with a range of 90.0 to 103.7%. Of the total 14C recovered from steers slaughtered 120 and 168 hr. after dosing, 98.5 and 99.5%, respectively, were in the excreta. For all animals, fecal excretion was two to three times that in the urine, and the gastrointestinal contents were the major reservoir of unexcreted 14C. A minimum of 85% of the 14C in feces was characterized as free DES by thin-layer chromatography (TLC). The 14C in the urine was not free DES; but after incubation with ß-glucuronidase-aryl sulfatase enzyme, a minimum of 85% was recovered as free DES (characterized by TLC). The concentrations of 14C were always higher in the liver, kidney and bile-gallbladder than in any other tissue analyzed. 14C-DES was recovered from hydrolysates of liver extracts and of bile-gallbladder extracts from several steers. Isotopic dilution procedures were the basis for these identifications. One of the liver samples from which 14C-DES was recovered came from a steer that was slaughtered 168 hr. after dosing with 14C-DES. Approximately 22% of the 14C in this liver sample was identified as 14C-DES, and this is an equivalent concentration of the order of 0.1 ppb DES. Analyses that employed gasliquid chromatography detected DES (0.9 to 1.2 ppb) in the livers from one steer slaughtered 72 hr. and another 120 hr. after ingestion of DES had ceased, but these analyses did not detect DES in livers of two steers slaughtered 168 hr. after DES ingestion had ceased. Copyright © 1974. American Society of Animal Science . Copyright 1974 by American Society of Animal Science.