Luteinizing hormone, prolactin and ovarian 20 alpha-hydroxysteroid dehydrogenase activities during pregnancy or pseudo-pregnancy in the rat

Pinealectomy-Induced Changes in Blood and Pituitary Luteinizing Hormone and Prolactin Levels During the Last Phase of Pregnancy in Rats

“…The serum LH and Prl levels, which are low from day 5 after conception, increase severalfold a few days before parturition [Amenomori et al, 1970;Linkie and Niswender, 1972;Bast and Melampy, 1972;Morishige et al, 1973] and are accompanied by a simultaneous decrease in the high pituitary contents of these hor mones and FSH [Ota et al, 1974;Nir et al, 1977;Tigchelaar and Nalbandov, 1975]. More over, the higher serum concentrations of pro gesterone (which inhibits LH release), decrease 3 to 4 days before parturition [Morishige et al, 1973;Me Cormack and Creenwald, 1974], while blood oestrogen levels increase during the same period [McCormack and Greenwald, 1974;Shaikh, 1971].…”

Influence of the estrous cycle at gamma‐ray exposure on radiation‐induced mammary tumorigenesis in virgin rats

“…The highest incidence of mammary tumors is observed in rats irradiated in late pregnancy and then treated with diethylstilbestrol (DES) as promoter (Inano et al, 1991). During pregnancy, the concentration of estradiol and progesterone in serum is gradually increased (Inano et al, 1991), but no change in the prolactin level is observed (Bast and Melampy, 1972). Many investigators show that estradiol induces end-bud development and duct elongation in mammary glands (McManus and Welsch, 1981), that progesterone promotes duct enlargement (McManus and Welsch, 1981) and that glucocorticoids stimulate alveolar development in the presence of prolactin (Kamiya et a/., 1991).…”