Role of luteal biosynthesis of prostaglandin F2α on function and structure of the corpus luteum during luteolysis in heifers

Abstract The role of endogenous prostaglandin F2α (PGF) in the induction of luteolysis by exogenous PGF was studied by simultaneous inhibition of endogenous PGF with flunixin meglumine (FM). Groups were controls (n = 8), PGF treated (n = 8), and FM + PGF treated (n = 9). Treatments were given 10 d postovulation at hours 0, 8, and 16. The protocol was based on (1) the assumption that luteolytic characteristics of exogenous PGF would be altered if the synthesis of endogenous PGF is simultaneously inhibited and (2) the reports that luteolysis involves a direct effect of uterine PGF on large luteal cells followed by an effect of the large cells on the small cells. At hour 48, progesterone concentration was greater in the controls (7.6 ± 0.8 ng/mL) than that in the FM + PGF group (3.0 ± 0.5 ng/mL) and lower in the PGF group (0.7 ± 0.3 ng/mL) than in the FM + PGF group (interaction, P P P