Expression of progesterone receptor related to the polymorphism in the PGR gene in the rabbit reproductive tract1

The association of the 2464G > A SNP found in the promoter region of the rabbit progester- one receptor gene with progesterone receptor (PR) ex- pression was evaluated by Western blot analysis. This SNP was associated with 2 lines divergently selected for uterine capacity, the high line selected to increase uterine capacity and the low line selected to decrease uterine capacity. Two progesterone isoforms were ob- tained using a commercial monoclonal antibody: the PR-B isoform described previously in rabbits, and the PR-A isoform, not described previously in rabbits. The GG genotype, the genotype more frequent in the high line, showed less PR-B and PR-A expression than the AA genotype in the oviduct (GG/AAPR-B = 0.81 and GG/AAPR-A = 0.73) and uterus (around 0.70 in both isoforms). The GA genotype showed similar PR-A ex- pression in both tissues and also similar PR-B expres- sion in the oviduct to the GG genotype. Conversely, the GG genotype showed less PR-B expression than the GA genotype in the uterus (GG/GAPR-B = 0.79). Similar expression of both PR isoforms was found in the uterus at d 2 and 3 of gestation; meanwhile, an increase of both isoforms was observed in the oviduct. Similar PR-A expression was observed in the ampulla and isthmus; meanwhile, the PR-B expression in the isthmus was double that in the ampulla.