Uptake of Oestradiol by Rat and Hamster Uteri in Vitro: Effects of Ethynyl Oestradiol and an Anti-Oestrogen

Abstract

Oestrogenic and anti-oestrogenic compounds that are effective antifertility agents for rats do not necessarily behave in a similar way for hamsters. The target tissues in the hamster are less sensitive to oestrogens and respond less to anti-oestrogens than those in the rat (Giannina, Butler, Popick & Steinetz, 1971). These investigators suggest that differences in metabolism or oestrogen affinity may explain their observations. Experiments in vivo show that hamster uteri retain significantly less tritiated oestradiol than is retained by rat uteri under identical experimental conditions (Ciaccio & Lisk, 1972). Prasad, Orsini & Meyer (1960) have shown that, unlike the rat, oestrogen is not required for implantation in the hamster.In the present investigation, the uptake in vitro of tritiated oestradiol and the effects of ethynyl oestradiol or the anti-oestrogen, (1-[2-(p-{\g=a\\x=req-\ (p-methoxyphenyl)-\g=b\-nitrostyryl}-phenoxy)ethyl]pyrrolidine monocitrate), on this uptake were compared in rat and hamster uterine tissue.A tritiated oestrogen ([6,7-3H]oestradiol-17\g=b\; 40 Ci/mmole; New England Nuclear Corp., Boston, Mass.) with radiochemical purity \m=ge\96\m=.\8% and radi oisotopic purity > 99% was used in these in-vitro studies. Benzene : ethanol (9:1) was used to dilute the tritiated oestradiol so that 0\m=.\16 ml of the diluted isotope in 400 ml incubation medium gave a final oestradiol concentration of 10\ m=-\ 10m.The in-vitro system used for the uptake of tritiated oestradiol by uterine tissue was described by Jensen, De Sombre, Hurst, Kawashima & Jungblut (1967). Uteri were obtained from immature (40 to 50 g) Sprague-Dawley derived rats and outbred Lak : LVG golden hamsters. The slit uterine horns were stirred in beakers containing Krebs-Ringer-Henseleit glucose buffer (pH 7-3) at 37°C. Each beaker contained twenty uterine horns in 400 ml buffer with 10-10 M-tritiated oestradiol. The effects of the oestrogen and anti-oestrogen on the uptake in vitro of the tritiated oestradiol were determined by adding unlabelled ethynyl oestradiol (10-9 m) or CN-55945-27 (20 µg|ml or 3-14 -5 m) to the incubation medium. Five uterine horns were removed from each beaker at the end of each specific time period, frozen in a dry ice-acetone bath * Present address :

Effects of the antiestrogens, MER-25 and CI 628, on rat and hamster lordosis

“…Available evidence suggests that hamsters are less sensitive than rats to the behavioral and physiological effects of estrogen Giannina, Butler, Popick, and Steinetz, 1971;Perry and Ferguson, 1974). This differential hormone sensitivity is reflected in a variety of ways.…”