THE STERILITY IN RABBITS PRODUCED BY INJECTIONS OF OESTRONE AND RELATED COMPOUNDS

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Abstract
Injections of large amts. of estrone into bred rabbit does both before and during the period of cleavage in no way affected the normal cleavage rate. The embryos died in early blastocyst stages and the period of maximum susceptibility to estrone sterilization occurred during the 3d and 4th days post coitum when the germinal vesicles were forming. Large dosages of estrone (up to 3000 R.U.) given before mating did not prevent ovulation. Ova cultured in vitro with estrone and estriol added to the medium went through the cleavage stage at the normal rate. Estriol also did not affect blastocyst differentiation in vitro. Ova transplanted into the fallopian tubes of a rabbit doe on heat cleaved normally but died in early blastocyst stages. The red vital dye made by coupling estrone with the diazo compound of para-chloro-aniline did not enter the ova when injected in 50-100 mgm. dosages; none the less these dosages were partially sterilizing. Complete prevention of implantation was had with the daily injection of 150 R. U. of estrone-in-oil on days 3 and 4 post coitum. Complete prevention of implantation was not had with daily dosages of 200 R. U. on days 5 and 6 post coitum. Estrone-in-oil was more effective than estrone in aqueous alkaline solution. The injection of less than 150 R. U. per day on days 3 and 4 post coitum resulted in a reduction in the number of implantations. The lower the dosage, the nearer to unity was the implantation ratio (number of implantations/number of corpora lutea), but the proportionality was not direct since lower dosages (above a minimum of 25 R. U. per day) were relatively more effective than higher dosages. The implantations observed appeared normal and gave rise to normal young. Dihydroestrone was approximately 3 times as effective as estrone in preventing implantation. Estriol was 1/4 to 1/5 as effective.

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