Abstract
4.5 μc (150 μg) of 17β-estradiol-4- 14C were administered intravenously to a heifer on days 8, 13 and 16 of one estrous cycle and days 0, 3, 6, 9, and, 14 of the next succeedings cycle. Radioactivity was present in the urine within 30 min. after the start of infusion. Total urinary 14C excretion averaged 22.4, 30.0, 33.6 and 35.4% of the administered dose at 12, 24, 48 and 72 hours post-injection. Three day cumulative excretion values ranged from 24.6% for the day 8 injection to 44.2% for the day 16 injection. Peak excretion fo radioactivity occured at 8–10 hours after the start of injection. A large quantitative peak of total estrogen excretion during the three days immediately preceding ovulation and a secon smaller peak occured 6–10 days following ovulation. 17α-Estradiol, 17β-estradiol and estrone comprised, respectively, 81, 3 and 12% of the day 8 urinary estrogen and 86, 2, and 8% of the day 16 estrogen. These labelled metabolites were definitely identified and found conjugated principally to glucuronic acid.
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