Immunolocalization, gene expression, and enzymatic activity of cyclooxygenases, prostaglandin e2-9-ketoreductase, and nitric oxide synthases in Mediterranean buffalo (Bubalus bubalis) corpora lutea during diestrus.

Immunopresence, gene expression, and enzymatic activity of cyclooxygenase 1 (COX1), COX2, PGE2-9-ketoreductase (PGE2-9-K), endothelial (eNOS), and inducible nitric oxide synthases (iNOS), and hormone in vitro production were examined in early, mid, late, and regressive buffalo corpora lutea (CL). COX1 immunosignals were detected in the cytoplasm of small luteal cells, COX2 in large luteal cells, and PGE2-9-K in all luteal cells. COX2 and PGE2-9-K immunosignals were greater in late CL. Immunopresence of both NOS types were evidenced in the nuclei and cytoplasm of all luteal cells, as well as in the nuclei of endothelial cells, during all stages studied. The eNOS and iNOS immunosignals increased during the early stage. COX1 transcripts were lower in late and regressive CL, COX2 in late, PGE2-9-K higher in regressive, and iNOS higher in early and lower in regressive CL. COX1 enzymatic activity was lower in regressive CL, COX2 increased in mid and late stages, and PGE2-9-K was higher in late CL. Endothelial NOS activity was higher during mid and late stages and lower in regressive, whereas iNOS was greater in late and lower in early. Progesterone in vitro release was higher in mid and lower in late phase, while PGF2α synthesis was higher in late CL and lower in regressive, and PGE2 was higher during regressive stage. These results support the idea that COX, NOS, and PGE2-9-K regulate buffalo CL life span. In particular, regressive CL seems involved in the development of the contralateral early CL, through the production of the luteotrophic PGE2.