Figure 2.

In situ hybridization of secretin messenger RNA (mRNA) in mouse uteri under delayed implantation. A, Mouse uterus under delayed implantation. Delayed implantation was induced by ovariectomizing pregnant mice at 08:30 to 09:00 am on day 4 of pregnancy and treated with daily injection of progesterone (1 mg/mouse; Sigma) at 09:00 from days 5 to 7. The mice were killed to collect uteri at 09:00 am on day 8 of pregnancy. B, Mouse uterus after delayed implantation was activated by estrogen treatment. To induce embryo implantation in these mice, estradiol-17β (25 ng/mouse; Sigma) was given to these progesterone-primed mice to initiate implantation on day 7 of pregnancy. The mice were killed to collect uteri 24 hours after estrogen treatment. Asterisk (*), embryo.