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

Abstract

To determine the physiological significance of tumour necrosis factor-alpha (TNFalpha) in the regulation of luteal functions in pig, this study was conducted to identify the presence of functional TNFalpha 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 TNFalpha in all samples (dissociation constant; 2.7 +/- 0.51 to 5.8 +/- 0.50 nM). The concentration of TNFalpha receptors was higher on day 15 of the oestrous cycle than on days 4 and 8 of the oestrous cycle (p < 0.05). Furthermore, TNFalpha 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 TNFalpha stimulated prostaglandin (PG) F2alpha and PGE2 secretion in a dose-dependent manner (p < 0.05). These results indicate that functional TNFalpha receptors are present in the porcine CL throughout the oestrous cycle and early gestation, and suggest that TNFalpha plays one or more physiological roles in regulating CL function throughout the oestrous cycle and the early gestation period. In addition, TNFalpha 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 TNFalpha plays a role in accomplishing luteolysis in the porcine CL.

Tumor Necrosis Factor-.ALPHA. (TNF.ALPHA.) Inhibits Progesterone and Estradiol-17.BETA. Production from Cultured Granulosa Cells: Presence of TNF.ALPHA. Receptors in Bovine Granulosa and Theca Cells

“…The affinities and concentrations of TNFα receptors in bovine granulosa and theca cells from all follicles examined in this study ranged between 4.7-6.9 nM and 13.7-31.3 pmol/mg proteins, respectively. T h e s e v a l u e s a r e c o m p a r a b l e w i t h t h e characteristics of TNFα receptors in the granulosa cells of pigs [19] and cows [8], and in the corpus luteum of pigs [20] and cows [13]. Previous studies have shown that bovine follicular fluid contains TNFα-like activity, and that the levels of TNFα measured in bovine follicular fluid [21] and serum [22] are comparable with the effective doses of TNFα and the affinity of TNFα receptors described in the present study.…”

Expression of factors associated with apoptosis in the porcine corpus luteum throughout the luteal phase of the estrous cycle and early pregnancy: Their possible involvement in acquisition of luteolytic sensitivity

“…Although specific binding sites for TNFa were found on the surface of porcine luteal and endothelial cells during the estrous cycle and pregnancy [37,38], there is no information about the expression of particular TNFRs subtypes in porcine CL. Since TNFR1 mediates apoptotic signals because of its possessing a death domain, the elevated expression of both TNFR1 mRNA and protein on Day 12 of the estrous cycle and its sudden decrease in the late luteal phase were unexpected.…”

Possible Actions of Tumor Necrosis Factor-.ALPHA. in Ovarian Function

“…Since TNFα and its receptors are present in atretic follicles [7,21], TNFα may be one of the local regulators that induce apoptosis at the t im e o f fo ll ic le at r es ia t h ro u gh it s plas m a membrane receptors. TNFα and TNFα receptors are evident in the early stage CL in cows [9], pigs [11,26], and humans [17]. TNFα is a potent stimulator of luteal prostaglandins (PGs) including PGF2α, PGE2, and PGI2 [9,33,34].…”