Temporal expression of progesterone and proteins associated with prostaglandin F2alpha-induced luteolysis in the sheep

To better understand the events associated with the functional and structural regression of the corpus luteum (CL), the temporal expression of steroidogenic acute regulatory (StAR) protein, progesterone (P4), matrix metalloproteinase (MMP)-2 and -9, tissue inhibitor of metalloproteinase (TIMP)-1 and -2, cyclooxygenase (COX)-1 and -2 was determined following three systemic infusions of PGF2alpha, in sheep. Luteectomies were performed at 0 hour (controls) or at -1, 1, 8, 16, and 24 hours relative to the third infusion of PGF2alpha. Plasma samples were also collected. StAR decreased 60 and 45% at the 16 and 24 hour time points, respectively, while P4 reached a nadir (25%) after the 8 hour time point before rebounding at the 24 hour time point. MMPs and TIMP-2 were unchanged. TIMP-1 decreased 30% at the 1 hour time point. COX-1 was undetectable while COX-2 results were inconclusive. Overall, 25% of sheep underwent luteolysis after three infusions of PGF2alpha.