lnterleukin-1β is a Potent Stimulator of Prostaglandin Synthesis in Bovine Luteal Cells1

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Abstract
Interleukin-1 (IL-1 ) is a polypeptide that has both local and systemic effects on numerous tissues, including endocrine cells. To evalute the effect of IL-1 on luteal function, bovine luteal cells were cultured for 5 days with increasing concentrations (0.1, 0.5, 1.0, 2.5, 5.0, 10.0 ng/ml) of recombinant bovine interleukin-1.beta. (rbIL-1.beta.). IL-1.beta. increased the production of luteal 6-keto-prostaglandin-F1.alpha. (6-keto-PGF1.alpha.), prostaglandin E2 (PGE2), and prostaglandin F2.alpha. (PGF2.alpha.) in a dose-dependent manner, but had no effect on progesterone (P4) production. Treatment with the cyclooxygenase inhibitor, indomethacin (5 .mu.g/ml), inhibited basal, as well as rbIL-1.beta.-stimulated prostaglandin production. Addition of Iloprost (a synthetic analogue of prostacyclin, 5 ng/ml) suppressed basal production of PGF2.alpha. and PGF2, but did not reduce the stimulatory effect of rbIL-1.beta.. Similarly, PGF2.alpha. suppressed basal, but not IL-1.beta.-stimulated, production of 6-keto-PGF1.alpha.. PGE2 had no effect on the synthesis of either PGF2.alpha. or 6-keto-PGF1.alpha.. P4 (1.75 .mu.g/ml) reduced basal as well as rbIL-1.beta.-stimulated production of 6-keto-PGF1.alpha., and PGF2.alpha.. These results indicate that IL-1.beta. could serve as an endogenous regulator of luteal prostaglandin production. It appears that IL-1.beta. action is not modified by exogenous prostaglandins, but is at least partially regulated by elevated P4. It is posible that the role of IL-1.beta. in stimulation of luteal prostaglandin production may be confined to a period characterized by low P4 levels, such as during luteal development or regression.