title: Critical progesterone requirement for maintenance of pregnancy in ovariectomized rats.
abstract: The minimum progesterone concentration required to maintain the pregnancy was studied by varying doses of progesterone given subcutaneously to rats ovariectomized on Day 8 of pregnancy. Injecting 3 mg progesterone plus 200 ng oestradiol benzoate daily provided serum progesterone values between 25.4 +/- 7.0 and 35.2 +/- 6.2 ng/ml throughout Days 10-19 which were significantly lower than normal levels (P less than 0.05), but resulted in 93.6% of fetal survival on Day 19 which was not significantly different from 93.3% in the control group. Injecting 2 mg progesterone plus 200 ng oestradiol benzoate daily gave progesterone values between 13.2 +/- 4.6 and 19.0 +/- 6.2 ng/ml and could not maintain fetal viability to Day 19 (14.2%, P less than 0.05 compared with control group). Critical times to supplement progesterone in rats ovariectomized on Day 8 or Day 15 were studied by varying the time of progesterone implantation after ovariectomy. Progesterone implants were administered 8, 12 and 24 h after ovariectomy on Day 8 and 24, 36 and 48 h after ovariectomy on Day 15. On Day 8, progesterone replacement could be delayed to 8 h but not 12 h, while on Day 15, progesterone replacement could be delayed up to 36 h but not 48 h after ovariectomy without affecting fetal survival.
authors.affiliation: School of Pharmacy, Robert Gordon's Institute of Technology, Aberdeen, UK.
authors.forename: W
authors.initials: W
authors.lastname: Arkaravichien
authors.forename: K E
authors.initials: KE
authors.lastname: Kendle
mesh_terms: D000818:Animals; D005260:Female; D005313:Fetal Death; D010052:Ovariectomy; D011247:Pregnancy; D011255:Pregnancy Maintenance / Q000502:physiology*; D011374:Progesterone / Q000097:blood / Q000494:pharmacology / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
chemical_list: D011374:Progesterone