CLONING, DEVELOPMENTAL EXPRESSION, AND IMMUNOHISTOCHEMISTRY OF CYCLOOXYGENASE-2 IN THE ENDOMETRIUM DURING EMBRYO IMPLANTATION AND GESTATIONIN THE MINK (MUSTELA-VISON)

Cyclooxygenase (COX) is the first rate-limiting enzyme in the biosynth esis of PGs. There are two isoforms, COX-1, a constitutive enzyme and COX-2, the induced form, products of two different genes. In this stud y, we report COX-2 complementary DNA cloning, uterine expression, and immunohistochemical localization in the mink uterus during postimplant ation gestation. The open reading frame of mink COX-2 contains 1812 nu cleotides encoding 604 amino acids. The homologies are 86%, 83%, 83%, 83%, 85%, and 84% in nucleotides and 86%, 87%, 87%, 85%, 86%, and 88% in amino acids with human, mouse, rat, guinea pig, sheep, and rabbit, respectively. All domains associated with biological activity are cons erved in the mink. Northern analysis revealed a transcript of 4.2 kb f or COX-2 in mink uterus and adrenal. Semiquantitative RT-PCR showed th at COX-2 messenger RNA is not present during diapause. The abundance o f COX-2 messenger RNA reached its maxima (P < 0.05) on days 3-5 of pos timplantation, gradually decreased through day 9, and was not present thereafter. By immunohistochemistry, COX-2 was present in uterine epit helium, stroma, and necks of endometrial glands at sites of implantati on. COX-2 expression appears to be induced in the endometrium by the e mbryo and may play a role in implantation and placentation in the mink .