mRNA and Protein Expressions of Prostaglandin E2 Receptors (EP2 and EP4), Cyclooxygenase-2 and Prostaglandin E Synthase in the Cervix of Cyclic Bitches and those with Pyometra

Abstract

_{Prostaglandins play a vital role in regulation of cervical patency. Prostaglandin E2 (PGE2) synthesis is regulated by cyclooxygenase (COX) and prostaglandin E synthase (PGES). PGE2 acts through prostaglandin E
receptors (EP), EP2 and EP4, to stimulate muscle relaxation. The aim of this study was to investigate mRNA expressions (EP2, EP4, COX-2, and PGES) and protein expressions (EP2, EP4, and COX-2) in the bitch cervix. Two groups of bitches, normal cyclic bitches and bitches with pyometra, were studied. Cyclic bitches were categorized into anestrus (n = 10), estrus (n = 7), and diestrus (n = 11), whereas bitches with pyometra were defined as open- (n = 18) or closed-cervix pyometra (n = 8) depending on the presence or absence of vaginal discharge, respectively. Cervices
from the internal to external os were collected immediately after ovariohysterectomy. RNA extraction from cervical tissue was determined for levels of EP2, EP4, COX-2, and PGES mRNA using real-time qPCR. Western blot was performed to evaluate the protein expressions of EP2, EP4, and COX-2. There were no differences of mRNA and protein expressions in the bitch cervix among the stages of the estrous cycle. However, the expressions of PGES mRNA was higher in the cervix of bitches with open-cervix than closed-cervix pyometra (p < 0.05). The differences of
protein expressions of EP2, EP4, and COX-2 were not observed. Our findings suggest that mRNA and protein expressions of the enzymes involved in PGE2 synthesis and PGE2 receptors are not influenced by hormonal status during the estrous cycle whereas PGES mRNA expression is likely associated with cervical relaxation in the bitches with pyometra.}