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Teratogenicity to 35-Day Fetuses, Excretion Patterns and Placental Transfer in Beef Heifers Administered 4-TERT-Butyl-2-Chlorophenyl Methyl Methyl-Phosphoramidate (Ruelene^r)

U. S. Department of Agriculture, Beltsville, Maryland 20705

Abstract

Three trials were conducted to study the teratogenicity, excretion and placental transfer of Ruelene³ in beef females. In trial 1, Ruelene and saline (control) were injected into either the jugular vein or amnionic sac of pregnant cows at 35 days of gestation (eight cows per treatment). Fetuses from all treatments were taken by cesarean section at 180 days of gestation and found to be similar in weight and size with no anatomical abnormalities resulting from the Ruelene injections. In trial 2, the excretion pattern of radiocarbon after the oral administration of ¹⁴C-Ruelene to two beef heifers was studied. Tail blood from these heifers sampled after dosing at 2, 4, 6, 8 and 24 hr. and then daily showed that the highest concentration of radiocarbon was in the 8 hr. samples. Sixty-two percent of the dose was excreted in urine within 24 hours. Approximately 84% of the dose was excreted within 5 days (74% in urine and 10% in feces). A very minor amount was excreted in respired CO₂. In trial 3, the placental transfer of radiocarbon after the intravenous injection of ¹⁴C-Ruelene into four pregnant heifers was studied. The data indicated that Ruelene or its metabolites, or both, are transferred across the placental barrier, but the fetus is probably protected from a large part of a single maternal dose because of rapid metabolism and excretion by the dam.

¹ Agricultural Research Service, Nutrition Institute, Ruminant Nutrition Laboratory, Beltsville, Maryland 20705.

² Present address: Bureau of Veterinary Medicine, Food and Drug Administration, 5600 Fishers Lane, Rockville, Maryland 20852.