Secretion of prostaglandins and progesterone by cells from corpora lutea of mares.

This research explores the secretion of prostaglandins and progesterone by cells from the corpora lutea of mares, suggesting that these might contribute to the control of luteal function and their changing ratios might impact the lifespan of the corpora lutea more than their absolute concentrations.

Study Methodology

• Cells were collected from the corpora lutea (CL) of mares during different stages of their reproductive cycle: early (Day 4-5), mid- (Day 8-9), and late (Day 12-13) dioestrus.
• Different cell populations were obtained by enzymic digestion of tissue. Two distinct luteal cell populations were observed – large cells and small cells.
• The researchers noted that the proportion of small luteal cells increased as the age of CL advanced.
• These cells from CL were incubated for 24 hours and secretions were analyzed for prostaglandin (PG) F, PGE-2, and 6-keto-PGF-1 alpha (the stable metabolite of prostacyclin).

Key Findings

• The cells from the mares’ CL produced higher concentrations of all prostaglandins during the early stage of dioestrus than during the mid- or late stages.
• The ratio of PGF to PGE-2 increased from 0.33 in the early stage of dioestrus to 1.34 in the mid stage, while the ratios of PGF to 6-keto-PGF-1 alpha remained relatively constant at approximately 0.6.
• The ratio of PGE-2 to 6-keto-PGF-1 alpha decreased between the early stage (3.27) and the mid-stage (0.43) of dioestrus.
• The addition of luteinizing hormone (LH), dibutyryl-cAMP (dbcAMP), or ionophore to cell cultures did not consistently affect the secretion of progesterone or prostaglandins by luteal cells.

Conclusions

• The study suggests that the prostaglandins produced by the luteal cells of mares may contribute to the control of luteal function.
• Furthermore, the research posits that the changing ratios of various prostaglandins might have a more significant impact on the lifespan of the CL than the absolute concentrations of each individual prostaglandin.

The research provides insight into the functioning of cells at different stages of mares’ reproductive cycle and opens avenues for further exploration into the role of prostaglandin and progesterone in reproductive health.