The Effects of Steroid Sex Hormones on Pregnant Rats

Abstract

Single doses of up to 0\ m=. \ 4mg/kg oestrone injected s.c. were found to interfere with pregnancy in the rat up to the 11th day post coitum (p.c.). As little as 0\m=.\02 mg/kg was effective during the period of tubal transport, while 0\m=.\1 mg/kg was necessary to prevent implantation after the ovum was free in the uterus. After implantation had taken place, 0\m=.\4 mg/kg injected on days 8, 9 or 10 destroyed some or all embryos or, if injected on days 10 or 11, caused delay in parturition. Delay in parturition was no longer reliably produced by the injection of 0\m=.\4mg/kg on the 16th day of gestation.A single dose of 4\m=.\0 mg/kg testosterone prevented implantation in 75 % of rats if injected s.c. during days 5-8 p.c., and produced either foetal loss or delay in parturition in 69 % of rats when injected on days 9-11 p.c. A single dose of 20 mg/kg testosterone was effective in all rats tested in preventing implantation if injected on days 1 and 5, producing foetal loss if injected on day 9 or delaying parturition if injected on days 11 and 16.A single dose of 4\m=.\0 mg/kg androst-5-ene-3\g=b\,17\g=b\-diolprevented implantation or caused foetal loss in 93 % of rats injected on days 5-11 p.c. This hormone was considerably more potent in preventing implantation and causing foetal loss than its androgenic potency as compared with testosterone would suggest. In contrast to testosterone, androst-5-ene-3\g=b\,17\g=b\-diol did not cause delay in parturition at doses up to 20 mg/kg. The effects of two other steroids tested, androst-4-ene-3,17-dione and 17\g=a\-methyl \x=req-\ androst-5-ene-3\g=b\,17\g=b\-diol, on pregnant rats were equivalent to or less than their androgenic potency would suggest.

Pregnancy-Terminating Effect of Human Chorionic Gonadotrophin in Rats

“…Dreisbach (1959) was successful in interrupting pregnancy in rats with a single subcutaneous dose of 0-4 mg oestrone/kg up to Day 11 post coitum. Alteration of physiological levels of endogenous LH, prolactin (Mantalenakis, 1968;MacDonald et al, 1970;Raj & Moudgal, 1970) and increased production of intrauterine luteolytic substance(s) (see Fajer, 1972) after a single dose of HCG have also been suggested.…”

The Implantation Reaction

“…It has been known for many years that the administration of large doses of estrogen prior to implantation prevents attachment of the blastocyst and decidualization of the stroma. (Parkes et aI., 1938;Dreisbach, 1959;Smith and Biggers, 1968). Similarly, if excessive estrogen is given to ovariectomized, progesterone-treated animals, it is not possible to elicit a decidual response either to trauma (Rothchild et aI., 1940;Velardo and Hisaw, 1951;Finn and Emmens, 1961;Stone and Emmens, 1964) or to oil (Finn and Emmens, 1961;Stone and Emmens, 1964).…”

Untersuchungen über den Einfluß des östrogens auf die Ovo – Implantation bei der Maus

“…Nach verschiedenen Autoren wirken Östrogene in der Präim plantationsphase schädigend auf die Keime, die Tubenwande rung und die Nidation, so daß es nicht zur G ravidität kom mt (Smith 1926, Dreisbach 1959, Parkes und Bellerby 1927, Burdick, W hitney und Pincus 1937, Smithberg und Runner 1956, Whitney und Burdick 1938, Parkes, üodds und Noble 1938, Courrier 1945). Da aber in unseren Versuchen die Dosis von 0,5 y bei nicht säugenden Weibchen und die fortgesetzte Ö.-d.-Zufuhr bei säugenden Tieren die Keime nicht zum Absterben brachte, können wir die schädigende W irkung, wenigstens für kleine Dosen, für die Maus nicht bestätigen.…”