Effects of in Vivo and in Vitro Administration of Prostaglandin F2α on Lipoprotein Utilization in Cultured Bovine Luteal Cells1

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Abstract
Two experiments were conducted to determine if a loss in the ability to utilize lipoprotein-cholesterol is one mechanism whereby prostaglandin F2 alpha (PGF2 alpha) decreases steroidogenesis in bovine luteal cells. In the first experiment, serum-free cultures of bovine luteal cells were treated with PGF2 alpha (100 ng/ml) for 5 days prior to addition of lipoproteins. Exposure to PGF2 alpha completely suppressed low-density lipoprotein (LDL)- and high-density lipoprotein (HDL)-stimulated progesterone production (p less than 0.01) compared to control (no PGF2 alpha) cultures. Luteal cells cultured in the presence of LDL + luteinizing hormone (LH, 10 ng/ml) + PGF2 alpha produced significantly less progesterone than luteal cells cultured with LDL + LH (p less than 0.05). Treatment with PGF2 alpha had no significant effect on HDL + LH-stimulated progesterone synthesis. In the second experiment, cows were injected with a luteolytic dose of PGF2 alpha (25 mg), and the corpora lutea were removed at 0 (no PG), 1, 4, or 12 h post-injection. Dissociated luteal cells were placed in culture for 7 days, either with or without LH (10 ng/ml), and lipoproteins were added on Days 5-7. LH stimulation of progesterone production was apparent in cultures obtained at 0 and 12 (p less than 0.05) but not 1 and 4 h post-PGF2 alpha. Addition of either LDL or HDL increased progesterone synthesis in all cultures, regardless of time following in vivo administration of PGF2 alpha. It is concluded that PGF2 alpha can inhibit bovine luteal cell utilization of either LDL or HDL in vitro. However, luteal cell utilization of lipoproteins in vitro is not adversely affected by in vivo exposure to PGF2 alpha, if collected within 12 h post-PGF2 alpha.