The ratio of the active progesterone receptor B isoform is higher in the ampullary region of the oviduct.
Purpose: To examine mRNA expression of progesterone receptor isoforms AB and B in oviduct mucosal tissue during the ovulatory cycle and in the different functional regions of the human oviduct.
Methods: The mucosal layer was isolated from human oviduct tissue and semi-quantitative RT-PCR for progesterone isoforms AB and B was performed. The RT-PCR results were verified by immunohistochemistry.
Results: The isthmic region showed no mRNA expression of either progesterone receptor isoform while the relative ratio of the B isoform was significantly higher in the ampullary region compared to the fimbrial region. There was a significant increase in the ratio of PRB to PRAB in the ampullary region compared to the fimbrial region in all samples.
Conclusions: We found an increase in the relative abundance of the progesterone receptor B isoform in the ampullary region which is the site of fertilization and early embryo cleavage. Our results indicate that progesterone responsive genes are more likely to be activated in the ampullary region of the oviduct due to the difference in PRAB to PRB ratio. Providing support for the hypothesis that progesterone may play a specific role in providing an appropriate environment for sperm capacitation, fertilization and early embryo cleavage.