Tumor necrosis factor-alpha and its receptor in bovine corpus luteum throughout the estrous cycle

The objective of this study was to investigate tumor necrosis factor alpha (TNF-alpha) expression, the presence of functional TNF-alpha receptors, and expression of TNF receptor type I (TNF-RI) mRNA in the bovine corpus luteu m (CL) during different stages of the estrous cycle. Reverse transcription (RT)-polymerase chain reaction (PCR) showed no difference in TNF-alpha mRNA expression during the estrous cycle. Concentrations of TNF-alpha in the CL tissue increased significantly from the mid to the late luteal stage and d ecreased thereafter (P < 0.05). An RT-PCR analysis showed higher levels of TNF-RI mRNA in CL of Days 3-7 than of other stages (P < 0.05). I-125-TNF-al pha binding to the membranes of bovine Ct was maximal after incubation at 3 8 degrees C for 48 h. The binding was much greater for TNF-alpha than for r elated peptides. A Scatchard analysis revealed the presence of a high-affin ity binding site in the CL membranes collected at each phase of the estrous cycle (dissociation constant: 3.60 +/- 0.58-5.79 +/- 0.19 nM). In contrast to TNF-RI mRNA expression, the levels of receptor protein were similar at each stage of the estrous cycle. When cultured cells of all luteal stages w ere exposed to TNF-alpha (1-100 ng/ml), TNF-alpha stimulated prostaglandin F-2 alpha and prostaglandin E-2 secretion by the cells in a dose-dependent fashion (P < 0.07), especially during the early luteal phase, although it d id not affect progesterone secretion. These results indicate the local prod uction of TNF-alpha and the presence of functional TNF-RI in bovine CL thro ughout the estrous cycle, and suggest that TNF-alpha plays some roles in re gulating bovine CL function throughout the estrous cycle.