Abstract
Although there is no acute luteolytic mechanism in the absence of pregnancy in the bitch a precise and well-timed embryo-maternal interaction seems to be required for the initiation and maintenance of gestation. Since only limited information is available about these processes in dogs, here, the uterine expression of possible decidualization markers was investigated during the pre-implantation stage (days 10-12) of pregnancy and in corresponding non-pregnant controls. Additionally, the expression of selected genes associated with blastocyst development and/or implantation was investigated in embryos flushed from the uteri used for this study (unhatched and hatched blastocysts). There was an upregulated expression of prolactin receptor (PRLr) and insulin-like growth factor 2 (IGF2) observed pre-implantation. The expression of PRL and of IGF1 was unaffected, and neither was the expression of progesterone- or estrogen receptor β (ERβ). In contrast, ERα-levels were elevated during early pregnancy. Prostaglandin (PG)-system revealed upregulated expression of PGE2-synthase and its receptors, EP2 (PTGER2) and EP4 (PTGER4), and of the PG-transporter. Elevated levels of PGF2α-synthase (PGFS/AKR1C3) mRNA, but not the protein itself, were noted. Expression of prostaglandin-endoperoxide synthase 2 (PTGS2,COX2) remained unaffected. Most of the transcripts were predominantly localized to the uterine epithelial cells, myometrium and, to a lesser extent, to the uterine stroma. PGES mRNA was abundantly expressed in both groups of embryos and appeared higher in the hatched ones. The expression level of IGF2 mRNA appeared higher than that of IGF1 mRNA in hatched embryos. In unhatched embryos IGF1, IGF2 and COX2 mRNA levels were below the detection limit.
Kautz, Ewa