EXCRETION OF RADIOCARBON OF 14C-LABELED 16-ALPHA,17-ALPHA-DIHYDROXYPROGESTERONE ACETOPHENIDE (DHPA) BY BEEF HEIFERS

This study investigated the excretion patterns of radiocarbon from beef heifers administered the progestogen DHPA and whether methoxychlor affected these patterns. Four heifers were given the estrus synchronization treatment consisting of feeding 120 mg. of unlabeled DHPA daily for nine consecutive days and an intramuscular injection of 5.0 mg. of estradiol valerate on the second day of DHPA treatment. Capsules of labeled DHPA were administered orally to two heifers each on the second and ninth days and one animal from each group received methoxychlor (112 mg. per kg. body weight, daily) during the nine-day treatment period. All of the label was recovered in the feces (97.4 to 97.9%) and urine (2.1 to 2.6%), and the average biological half-lives were 22.2 and 21.6 hours, respectively, for feces and urine. The administration of DHPA-4-14C on the second or ninth synchronization days of feeding methoxychlor had little effect on the fecal and urinary excretion patterns. © 1969, American Chemical Society. All rights reserved.