After 14C-estradiol-17β was injected into a hand vein of a pregnant baboon in the 157th day of gestation, the following steroids were isolated from the maternal urine: Estrone and estradiol from the unconjugated fraction, estrone, 2-methoxyestrone, estradiol, 15α-hydroxyestradiol, 16-ketoestradiol and estriol from the sulfate fraction, and estrone, 2-methoxyestrone, 16α-hydroxyestrone, estradiol, 16-ketoestradiol and estriol from the glucosiduronate fraction. Estrone was the most abundant estrogen in all three fractions. From the metabolites isolated it can be concluded that estradiol can be converted by the pregnant baboon to estrone and both estrone and estradiol-17β can undergo hydroxylations and conjugation. These data fit well with the observations that estradiol-17β is the most abundant estrogen found in the placenta of the baboon and estrone is found in the largest amount in pregnancy urine.
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