Intraluteal regulation of prostaglandin F2α-induced prostaglandin biosynthesis in pseudopregnant rabbits
2007
Zerani, M. | Dall'Aglio, C. | Maranesi, M. | Gobbetti, A. | Brecchia, G. | Mercati, F. | Boiti, C.
The objective of the present study was to investigate in rabbit corpora lutea (CL), at both the cellular and molecular level, intraluteal cyclooxygenase (COX)-1, COX-2 and prostaglandin (PG) E2-9-ketoreductase (PGE2-9-K) enzymatic activities as well as in vitro PGE2 and PGF2α synthesis following PGF2α treatment at either early- (day-4) or mid-luteal (day-9) stage of pseudopregnancy. By immunohistochemistry, positive staining for COX-2 was localized in luteal and endothelial cells of stromal arteries at both the stages. In CL of both stages, basal COX-2 mRNA levels were poorly expressed, but rose (P < 0.01) 4- to 10-fold 1.5-6 h after treatment and then gradually decreased within 24 h. Compared to mid-stage, day-4 CL had lower (P < 0.01) COX-2 and PGE2-9-K basal activities, and PGF2α synthesis rate, but higher (P < 0.01) PGE2 production. Independent of luteal stage, PGF2α treatment did not affect COX-1 activity. In day-4 CL, PGF2α induced an increase (P < 0.01) in both COX-2 activity and PGF2α synthesis, whereas that of PGE2 remained unchanged. In day-9 CL, PGF2α up-regulated (P < 0.01) both COX-2 and PGE-9-K activities, and PGF2α production, but decreased (P < 0.01) PGE2 synthesis. All changes in gene expression and enzymatic activities occurred within 1.5 h after PGF2α challenge and were more marked in day-9 CL. Our data suggest that PGF2α directs intraluteal PG biosynthesis in mature CL, by affecting the CL biosynthetic machinery to increase the PGF2α synthesis in an auto-amplifying manner, with the activation of COX-2 and PGE-9-K; this may partly explain their differentially, age-dependent, luteolytic capacity to exogenous PGF2α in rabbits.
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