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Is interleukin-1 a luteotrophic or luteolytic agent in cattle?

Department of Reproductive Immunology and Pathology, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, 10-747 Olsztyn, Poland
¹ Laboratory of Reproductive Endocrinology, Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan

Correspondence should be addressed to D J Skarzynski; Email: d.skarzynski{at}pan.olsztyn.pl

Cytokines are thought to regulate prostaglandin (PG) secretion in the bovine endometrium. However, there is no consensus about the role of interleukin-1 (IL1A) on PG secretion. The objective of this study was to examine the influence of IL1A on basal and interferon- (IFNT)-regulated PG in vitro secretion, as well its effects on PG secretion, progesterone (P₄) output, and corpus luteum (CL) in vivo lifespan. Explants of bovine endometrium (days 16–17 of the estrous cycle or early pregnancy) were stimulated with IL1A (10 ng/ml), IFNT (30 ng/ml), or IL1A combined with IFN. IL1A alone strongly stimulated luteotrophic PGE₂ secretion by endometrial tissues of both pregnant and nonpregnant cows. IL1A also stimulated luteolytic PGF₂ output in the late luteal phase. IFNT augmented the stimulatory effect of IL1A on PGE₂ secretion. In an in vivo experiment, saline or IL1A at different doses (0.001–10 µg/per animal) was applied to the uterine lumen on day 16 of the cycle. Only the highest dose of IL1A caused a temporal increase in PGF₂ secretion, while it had no effect on P₄ secretion or CL lifespan. Application of 0.1 and 1 µg IL1A stimulated P₄ and PGE₂ output and prolonged the CL lifespan. Although IL1A may stimulate in vitro luteolytic PGF₂ secretion during the estrous cycle, it only acts as a luteotrophic factor in vivo. IL1A increased luteotrophic PGE₂ and P₄ output, inhibiting spontaneous luteolysis. These luteotrophic effects may result in appropriate luteal development and function in cows during the estrous cycle and early pregnancy.