Induction of catechol-O-methyltransferase in the luminal epithelium of rat uterus by progesterone.

We performed light microscopic immunocytochemical observations of the localization of catechol-O-methyltransferase (COMT) in rat uterus, using a rabbit anti-rat serum specific for the soluble form of rat liver COMT, biotinylated goat anti-rabbit immunoglobulin, and peroxidase conjugated with streptavidin. In the non-pregnant rat, COMT was minimal but detectable in the uterine luminal and glandular epithelium, with greater amounts present in uteri from rats in estrus than those in diestrus. In early pregnancy a robust accumulation of COMT was observed in the luminal epithelium. To more precisely define both the timing and the factors contributing to the appearance of COMT, uteri were examined on Days 1-5 in pregnant and pseudopregnant rats. Accumulation of COMT in the luminal epithelium was observed by Day 3 in uteri from pregnant and pseudopregnant rats and by Day 4 in lactating post-partum rats. No immunostaining of COMT was observed in uteri from non-lactating post-partum rats. Ovariectomy on Day 0 or 1 but not on Day 2 of pregnancy prevented the appearance of COMT on Day 4. Progesterone treatment immediately after ovariectomy on Day 0 or 1 of pregnancy restored the COMT.