Du Rôle De l'HYPOPHYSE Et Des Ovaires Dans La Biosynthèse Des Œstrogènes Au Cours De La Gestation Chez La Truie

Abstract

On peut conclure que, au cours de la gestation chez la Truie, l'ensemble faeto-placentaire possède les activités enzymatiques nécessaires à la synthèse des oestrogènes.

Influence of the fetal pituitary-adrenal axis on fetal and maternal progesterone and unconjugated oestrogen concentrations in the pig

“…The rapid decrease in oestrogens after parturition suggests that they are produced by the gravid uterus (Fèvre et al, 1968;Robertson & King, 1979) and the negative arterio-venous difference in the uterine and umbilical circulations (Silver et ., 1979) indicates their placental origin. The high oestrogen content of placental tissue (Choong & Raeside, 1974) and the demonstration that fetal placental tissue can convert androstenedione (Ainsworth & Ryan, 1966) or pregnenolone (Craig, 1982) to oestrogens are additional evidence for the placental synthesis of oestrogens in the pig.…”

“…Maternal oestradiol-17ß concentrations have been shown to be lower in gilts carrying small numbers of hypophysectomized fetuses than in those carrying small numbers of normal fetuses (Kendall, Dziuk, Nelson & Thurmon, 1985). The placenta is the major source of oestrogens during gestation in the pig (Fèvre, Léglise & Rombauts, 1968;Robertson & King, 1974) and Craig (1982) showed that the placenta has limited enzymic ability to synthesize oestrogens from pregnenolone by the A4-pathway in vitro. Moreover, the activity of those enzymes essential for the metabolism of progesterone to oestrone increased at term.…”

INHIBITION OF 3β‐HYDROXYSTEROID DEHYDROGENASE IN THE SOW NEAR TERM: EFFECTS ON FETAL AND MATERNAL STEROIDS AND ON DELIVERY

“…The other major group of steroids likely to be affected by inhibition of 3fl-HSD are the oestrogens which are produced by the feto-placental unit in the sow (Fevre, Leglise & Rombauts, 1968;Choong & Raeside, 1974). Oestrone is the predominant oestrogen during late pregnancy in the pig; its concentration rises gradually towards term and is thus associated with the concomitant increase in fetal plasma cortisol (Robertson & King, 1974;Silver et al 1979).…”

Differential patterns in luteal prolactin and LH receptors during pregnancy in sows and ewes

“…Oestrogens, which are luteotrophic in the intact sow (Kidder, Casida & Ruimmer, 1955;Gardner, First & Casida, 1963), are produced by the placenta in this species and increase at Days 25 and 70 (Fèvre, Leglise & Rombauts, 1968 (Goldenberg, Bridson & Köhler, 1972) and stimulate 125I-labelled LH binding to dispersed granulosa cells (Nakano, Akahori, Katayama & Tojo, 1977) and luteal membranes (Garverick, Polge & Flint, 1982) in the sow. Oestrogens also play a role in prolactin receptor regulation, as demonstrated in pig granulosa cells at the time of luteinization (Hammond & Krall, 1979).…”