Regulation of prostaglandin synthesis by interleukin-1α in bovine endometrium during the estrous cycle

Interleukin (IL)-1 has been suggested to participate in regulation of many reproductive functions. To investigate the possible role of IL-1α as a local regulator in bovine endometrium, we determined the effects of IL-1α on prostaglandin (PG) E2 and PGF_2α output by the bovine endometrium at different stages of the estrous cycle. The expressions of IL-1α and IL-1 receptor type 1 (IL-1RT1) mRNA in bovine endometrium were also studied. Bovine uteri were classified into six stages (estrus: day 0; early luteal: days 2-3; developing luteal: days 5-6; mid luteal: days 8-12; late luteal: days 15-17; and follicular: days 19-21). After 1 h of pre-incubation, endometrial tissues (20-30 mg) were exposed to 0 or 10 ng/ml IL-1α for 4 h. IL-1α significantly stimulated PGE2 output throughout the luteal stages, with the highest response during the mid luteal stage, while it did not stimulate PGE2 output during the estrus and the follicular stage. On the other hand, IL-1α significantly enhanced PGF_2α output throughout the estrous cycle except in the endometrium from the mid luteal stage, with the highest response at the follicular stage (P < 0.001). The treatment of endometrial tissue with IL-1α resulted in an increase of the PGE2:PGF_2α ratio at the mid luteal stage, and in a decrease during the late luteal and follicular stages of the estrous cycle. A semiquantitative reverse transcription-polymerase chain reaction revealed that IL-1α and IL-1RT1 mRNA are expressed in the endometrium throughout the estrous cycle. IL-1α mRNA expression was greater in the early luteal stage than in the estrus, late luteal, and follicular stages (P < 0.05). IL-1RT1 mRNA was greater in the late luteal stage than in the other stages (P < 0.05). The overall results suggest that IL-1α is produced in bovine endometrium throughout the estrous cycle, and plays some roles not only in maintenance of CL, but also in luteolysis by regulating the local PGE2:PGF _2α ratio in bovine endometrium during the estrous cycle.