Influence of 20α-Hydroxy pregn-4-en-3-one on Deciduomal Response to Uterine Trauma in Immature Rats in the Presence of Progesterone

Abstract

In immature rats with ovaries strongly luteinized by injections of large doses of PMS and HCG, uterine traumatization fails to elicit formation of deciduomata, although the vaginal epithelium is definitely mucified in such animals, reflecting the combined effect of estrogen and progestin (Armstrong and Greep, 1965;Takewaki, 1969a) . As one of possible explanations for this failure of deciduomal response, Armstrong and G reep (1965) suggested an inhibitory effect of 20a-hydroxypregn-4-en-3-one (20a-OH-P) on deciduoma formation in the presence of progesterone.The experiments to be reported here were undertaken to explore possible interactions between the two steroids with respect to deciduomal reaction to uterine trauma in ovariectomized immature rats.Materials and methods. Immature rats of the T strain from the colony maintained in this laboratory were used in these experiments.They were housed in a temperatureand light-controlled room and given free access to standard chow and water.Five groups of rats were weaned and ovariectomized at 21 days of age. Subcutaneous injections of mixtures of two or three steroids were started 2 days after operation.Group I rats received daily injections of 2 mg progesterone and 0.2 pug estradiol-1713, whileGroup II animals 2 mg 20a-OH-P and 0.2 pg estradiol. In Groups III, IV and V, rats were given daily injections of 1, 2 and 5 mg 20a-OH-P, respectively, in addition to 2 mg progesterone and 0.2 pg estradiol.Daily doses were always dissolved in 0.15 ml sesame oil, regardless of the number of steroids combined.On the day of the 4th injection, uteri of all rats were traumatized via midventral laparotomy with the use of ether anesthesia. Uterine traumatization was achieved by scratching the endometrium of the right uterine horn along its entire length with a needle inserted into the lumen (For details of the technique, see Takewaki, 1969aTakewaki, , 1970. The animals were given injections of steroids for 3 days longer and