Luteotropic Action of Decidual Tissue in the Pregnant Rat

• Published in: Biology of reproduction Vol. 23; no. 3; pp. 507 - 512
• Main Authors: Basuray, R, Gibori, G
• Format: Journal Article
• Language: English
• Published: United States Society for the Study of Reproduction 01.10.1980
• Subjects: Abortion, Induced; Animals; Decidua - physiology; Ergolines - pharmacology; Female; Hysterectomy; Pregnancy; Pregnancy, Animal; Progesterone - blood; Rats; Transplantation, Homologous; Trophoblasts - physiology; Trophoblasts - transplantation
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod23.3.507

It has been reported that the rat placenta possesses luteotropic activity as early as Day 8 of pregnancy (Alloiteau, 1957; Kisch and Shelesnyak, 1967; Morishige and Rothchild, 1974). Since rat placental lactogen is undetectable at this stage of pregnancy by either bioassay or radioreceptor assay (Alloiteau and Mayer, 1967; Kelly et al., 1975) and since the decidual tissue of pseudopregnant animals sustains progesterone synthesis in the relative absence of prolactin (Gibori et al., 1974), it was of interest to determine the possibility of a similar luteotropic activity by the decidual tissue of the pregnant rat. Day 9 pregnant rats possessing only decidual tissue or trophoblast were obtained by either excising fetuses and trophoblast and maintaining the decidual tissue in situ or by removing the whole conceptuses and transplanting trophoblastic tissue subcutaneously. Control rats consisted of animals either bearing the whole placenta (fetuses removed), bearing no conceptuses (uterus completely evacuated), hysterectomized, or sham-operated. To suppress prolactin release, rats were injected s.c. with 0.4 mg ergocryptine (ECO) on Day 9 of pregnancy. Control rats were treated with the vehicle. Removal of the fetuses had no deleterious effect on progesterone secretion. However, when the whole conceptuses were removed, serum progesterone levels dropped by 25% within 24 h and remained at lower levels through Day 12 than in sham-control animals. In rats bearing only decidual tissue, the concentration of progesterone in the serum on Days 10 and 11 remained at levels found in intact pregnant rats. ECO treatment of sham-operated or fetectomized animals on Day 9 had no effect on serum progesterone, suggesting that either the placenta or prolactin is necessary for the maintenance of progesterone synthesis at this stage of pregnancy. However, when both prolactin and the conceptuses were removed by ECO treatment and hysterectomy or removal of conceptuses, serum progesterone decreased within 24 h to 8.5 ± 1.4 ng/ml and remained low through Day 12. In contrast, in decidua-bearing rats, serum progesterone concentration remained elevated 24 and 48 h after ECO treatment. Transplant of Day 12, but not Day 9, trophoblastic tissue to rats with the conceptuses removed also reversed the effect of ECO on progesterone. These findings indicate that the decidual tissue of pregnant rats maintains progesterone secretion in the relative absence of prolactin, and further suggest that a luteotropic hormone secreted in early pregnancy by the placenta is of decidual tissue origin.