Tumour Necrosis factor-α Receptors are Present in the Corpus Luteum Throughout the Oestrous Cycle and During the Early Gestation Period in Pigs

To determine the physiological significance of tumour necrosis factor‐α (TNFα) in the regulation of luteal functions in pig, this study was conducted to identify the presence of functional TNFα receptors in porcine corpora lutea (CL) throughout the oestrous cycle and the early gestation. The CL were isolated from pigs on days 4, 6, 8, 12 or 15 of the oestrous cycle (n=3; day 0 = oestrus) and days 15, 20 or 25 of gestation (n=3; day 0 = mating). A Scatchard analysis revealed the presence of a high‐affinity binding site for TNFα in all samples (dissociation constant; 2.7 ± 0.51 to 5.8 ± 0.50 nM ). The concentration of TNFα receptors was higher on day 15 of the oestrous cycle than on days 4 and 8 of the oestrous cycle (p < 0.05). Furthermore, TNFα receptor concentrations in the CL on days 15, 20 and 25 of gestation were significantly lower than on day 15 of the oestrous cycle (p < 0.05). On day 9 of the oestrous cycle, exposure of cultured luteal cells to 0.06–60 nM TNFα stimulated prostaglandin (PG) F_2α and PGE₂ secretion in a dose‐dependent manner (p < 0.05). These results indicate that functional TNFα receptors are present in the porcine CL throughout the oestrous cycle and early gestation, and suggest that TNFα plays one or more physiological roles in regulating CL function throughout the oestrous cycle and the early gestation period. In addition, TNFα receptor concentration in the CL of the late luteal stage (day 15) of the oestrous cycle was higher than on the respective day in the early pregnant pig, suggesting that TNFα plays a role in accomplishing luteolysis in the porcine CL.