Induction of implantation in the rat by intraparametrial injection of uterine RNA from oestrogen-treated animals.

Crude RNA preparations from uteri of oestradiol-treated rats induced the implantation of delayed blastocysts when injected into the parametrium of ovariectomized pregnant rats. Treatment of donor animals with labelled oestradiol showed that this effect could not be due to contamination of the RNA extracts by oestradiol. RNase digestion of these extracts suppressed their capacity to induce implantation. Purified poly (A)-rich RNA from oestrogen-treated uteri failed to elicit implantation although it was capable of increasing epithelial height when repeatedly injected into uterine horns of ovariectomized rats. These results suggest that uterine RNA synthesis might somehow mediate the effects of oestrogen in causing implantation and that RNAs other than messenger RNA might be involved.