The interleukin-1ß system in the corpora lutea of pigs during early pregnancy and the estrous cycle.

Expression of mRNAs encoding interleukin-1ß (IL-1ß), IL-1ß receptor I (IL-1RI), IL-1 receptor accessory protein (IL-1RAcP) and IL-1 receptor antagonist (IL-1Ra), as well as synthesis of IL-1ß and IL-1RI proteins, were examined in the corpus luteum (CL) during critical stages of CL activity on days 10-16 of pregnancy and 2-16 of the estrous cycle. Luteal cells were cultured in vitro with IL-1ß, and the effect on release of steroid hormones was determined. Expression of the IL-1ß system in the CL changed significantly during pregnancy and the estrous cycle. IL-1ß, IL-1RI, and IL-1Ra mRNA levels were elevated on days 12-13, whereas IL-1RAcP mRNA was increased on days 15-16 of pregnancy. In cyclic CL, expression of IL-1ß, IL-1RI, and IL-1RAcP mRNAs was increased on days 12-13. IL-1ß and IL-1RI protein were highest in the CL on days 10-11 and 8-11 of pregnancy and the estrous cycle. Luteal cells harvested from gravid and cyclic CL produced IL-1ß in vitro. IL-1ß increased progesterone and estradiol-17ß (E2) release by luteal cells on days 10-16 and 10-11 of pregnancy, respectively and on days 2-11 of the estrous cycle. IL-1ß decreased the level of E2 produced by regressed CL (days 15-16). Expression of the IL-1ß system in CL and IL-1ß secretion from luteal cells changed depending on the status of the CL. These data show that IL-1ß may be involved in intraluteal, luteotrophic regulation of CL functions in gravid and cyclic pigs.