Prostaglandin- and thromboxane-producing activity of isolated luteal cells from pseudopregnant rabbits

The pseudopregnant rabbit is proposed as a suitable model for studies on physiology and endocrinology of the luteal phase. Pseudopregnancy is defined by corpus luteum function from day 1 to day 12 post hCG, as demonstrated by peripheral progesterone concentrations. The corpus luteum is highly vascularized which is extremely important to ensure progesterone secretion. Prostaglandins are potent vasoactive compounds and may be involved in controlling the ovarian/luteal blood flow. The present studies were designed to investigate the capacity of luteal cells for their intracellular production rates of prostaglandins in the early luteal phase. Pseudopregnancy was induced with a subcutaneous injection of FSH/LH, followed two days later by an intravenous injection of hCG, on days 0, 1 to 4 of pseudopregnancy luteal cells were isolated and incubated for 4 days. Media were collected every 24 h and analyzed for prostaglandins. The luteal cells were characterized by immunocytochemistry and progesterone measurements. Cultured luteal cells were able to convert exogenously applied arachidonic acid into PGI2, PGE2, PGF2alpha, and TXA2. The major compound that could be detected in the culture medium and in the cells was PGI2. The absolute values of the production pattern varied in all experiments in the ranges PGI2 > PGE2 > PGF2alpha > TXA2 with the greatest difference on day 3. In view of this fact the corpus luteum may contribute locally synthesized prostaglandins to regulate its own function. The physiological meaning of these findings should now be studied in a more optimal environment such as organ culture.