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

Abstract

Expression of mRNAs encoding interleukin-1β (IL-1β), IL-1β receptor I (IL-1RI), IL-1 receptor accessory protein (IL-1RAcP) and IL-1 receptor antagonist (IL-1Ra), as well as synthesis of IL-1β 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-1β, and the effect on release of steroid hormones was determined. Expression of the IL-1β system in the CL changed significantly during pregnancy and the estrous cycle. IL-1β, 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-1β, IL-1RI, and IL-1RAcP mRNAs was increased on days 12–13. IL-1β 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-1β in vitro. IL-1β increased progesterone and estradiol-17β (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-1β decreased the level of E2 produced by regressed CL (days 15–16). Expression of the IL-1β system in CL and IL-1β secretion from luteal cells changed depending on the status of the CL. These data show that IL-1β may be involved in intraluteal, luteotrophic regulation of CL functions in gravid and cyclic pigs.