Expression of Prostaglandin-Synthesizing Enzymes (Cyclooxygenase 1, Cyclooxygenase 2) in the Ovary of the Quail (Coturnix japonica).

Cyclooxygenase is known to be the ratelimiting enzyme in the production of prostaglandins. So far, in different bird species there have been found two isoforms of cyclooxygenases (COX), cyclooxygenase 1 (COX-1) and cyclooxygenase 2 (COX-2). These isoforms along with prostaglandins are regarded to possess a determining influence on the success in female reproduction. Only in a few bird species the expression sites of cyclooxygenases have been investigated. In this study we report on the expression of COX-1 and COX-2 in the ovary of the quail (Coturnix japonica) using PCR, immunohistochemistry and non-radioactive in situ hybridization techniques. Using real time-polymerase chain reaction (RT-PCR), a distinct signal for COX-1 and COX-2 could be shown in small and large follicles of quail ovary. Antibodies to COX-1 distinctly labelled smooth muscle cells of the stroma, whereas COX-2 showed marked immunostaining in the thecal glands and the ovarian surface epithelium. In the same location, a signal of the corresponding mRNAs of COX-1 and COX-2 was found using in situ hybridization. This expression pattern in the quail is therefore completely different from the localization of COX-1 and COX-2 in the hen and ostrich, which suggests different functions of the cyclooxygenases in this small galliform avian species. According to our results, in quails COX-2 is involved in the synthesis of prostaglandins in the ovary's interstitial glands, which until now have been considered mainly as steroid-secreting cells. COX-1, which is expressed in the smooth muscles of the stroma, possibly plays a role in ovulation.