Control of Luteal Function During Early Pregnancy in the Guinea-Pig

Pregnant guinea-pigs were injected with oestrogen at different stages of gestation. After injections on Days 17 and 18 and on Days 25, 26, 32 and 33 peripheral maternal progesterone concentrations were lower than in control animals. Histology showed deleterious changes in the corpora lutea. After injections on Days 10 and 11 the maternal progesterone concentrations remained in the normal range for some time in 12 of 16 guinea-pigs and the corpora lutea appeared histologically normal. Oestrogen therefore affects the pregnancy differently at different stages of gestation.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of oestrogen on pregnancy of guinea-pigs

Evans¹,

Sin²,

Merrick³

et al. 1981

“…On the other hand, an ovariectomy at mid-pregnancy or the later trimester of pregnancy does not disrupt the process of pregnancy in several mammals, including humans (Csapo et al 1972), monkeys (Albrecht et al 2000), guinea pigs (Bland & Donovan 1969), and/or mares (Hinrichs et al 1987), whose progestin and estrogen are supplied by other tissues such as the placenta. In ovariectomized mares, a daily single injection of progesterone is sufficient to establish and maintain pregnancy after embryo transfer (Hinrichs et al 1987).…”

Section: Introductionmentioning

confidence: 99%

The complete control of murine pregnancy from embryo implantation to parturition

Terakawa¹,

Watanabe²,

Obara³

et al. 2012

The ovary is the main secretory source of progestin and estrogen and is indispensable to the maintenance of all events of pregnancy in mice. The purpose of this study was to control all processes of pregnancy in mice, from embryo implantation to parturition, without ovaries. The ovaries were removed before embryo implantation, and a single injection of medroxyprogesterone acetate (MPA) was given. Embryo implantation was induced by leukemia inhibitory factor, which can substitute 17b-estradiol (E 2 ). Continuous exposure to E 2 was necessary at mid-pregnancy, when placentation was completed. All mice sustained pregnancy without ovaries before parturition, which was initiated by the removal of E 2 and MPA. Murine pregnancy is a complicated process involving embryo implantation, placentation, and parturition. Complete control of pregnancy was achieved with the simple treatment of MPA and E 2 after induction of embryo implantation. Here, time-dependent events in the uterus during pregnancy could be realized without the ovaries, because the initiation of each event could be stringently controlled by hormonal treatments.

“…Observations were made on Days 5, 9 and 20 of pregnancy (in this species, pregnancy lasts an average of 63 days; Rowlands, 1949). By Day 5, luteinization is complete and a fully functional corpus luteum is present (Bland & Donovan, 1969;Challis et ai, 1971;Hilliard, 1973) and implantation has not taken place (Blandau, 1949). Studies on clomiphene-treated animals at this time should give evidence of interference with the preimplantation uterus and normal CL formation and function.…”

Section: Introductionmentioning

confidence: 99%

“…Studies on Day 9, when implan¬ tation has taken place (Days 6-7, Blandau, 1949) and implantation swellings are clear on the uterus, should give evidence for interference with implantation, decidualization and CL main¬ tenance. Between Days 9 and 20, progesterone becomes essential for pregnancy maintenance (Days 11-14, Loeb & Hesselburg, 1917;Deanesly, 1960Deanesly, , 1963bCsapo et ai, 1981), the conceptus produces a luteotrophic substance (Days 12-25, Bland & Donovan, 1969;Blatchley et ai, 1975;Antonini et ai, 1976;Poyser & Maule Walker, 1979) and the switch of progesterone secretion from CL to placenta takes place from Day 15, (Deanesly, 1960;Heap & Deanesly, 1966 (Orkzyk et al, 1979).…”

Section: Introductionmentioning

confidence: 99%

Effects of clomiphene citrate on early pregnancy in guinea-pigs

Motta

Hutchinson²

1991

Summary. Clomiphene citrate (2 mg/kg body wt) given on the day of mating can block or interrupt pregnancy in guinea-pigs. Corpus luteum function, uterine histology, implantation and embryo development were studied in clomiphene-treated and control animals on Days 5, 9 and 20 of pregnancy. Following treatment, only 25% of the females were regularly pregnant, presenting large and healthy foetuses. The other females examined showed either pregnancy with embryos undergoing resorption or no sign of pregnancy. In these females, corpus luteum size was reduced, progesterone concentrations were very low and the endometrial glands and the epithelium were often altered. It is concluded that clomiphene causes a reduction in fertility by altering the uterus and, by directly or indirectly inducing luteolysis, causes later pregnancy loss.