Prostaglandins and the regulation of parturition in mares.

This research article focuses on the role of prostaglandins in the mare, specifically throughout pregnancy and parturition. The study highlights how changes in prostaglandin concentrations, influenced by various hormonal factors and physiological processes, contribute to the initiation and progression of labor in mares, both at term and preterm.

Prostaglandins and Pregnancy

• Prostaglandins are vital during the perinatal period for mares. These compounds are typically present at low concentrations during most of the pregnancy period due to regulatory actions of progestagens—which are hormones related to progesterone. Progestagens suppress the enzymes that metabolize prostaglandins, controlling the amounts in the body.
• Toward the end of the pregnancy term, a gradual increase in prostaglandin concentrations is observed. This surge is largely associated with the activation of the fetal hypothalamo-pituitary-adrenal axis—a hormonal system involved in a variety of bodily functions, including stress responses and metabolisms, which could imply readiness for childbirth.
• Increased prostaglandin levels also correlate with the stimulation of the PGHS-2, a prostaglandin-synthesizing enzyme, and a shift in the balance between progestagens and oestrogens in favor of the latter. Oestrogens are female sex hormones that have multiple roles in pregnancy and labor.

Role of Cytokines and Prostaglandins in Parturition

• New findings suggest proinflammatory cytokines serve as vital intermediaries for prostaglandin synthesis during parturition. These immune system molecules appear to be significant both for deliveries at term in healthy mares and for preterm parturition associated with placental infection.
• Prostaglandin concentrations rise considerably during active labor, and taper off after birth, coinciding with the delivery of the placenta.

Prostaglandins and Labor Induction

• During labor inductions, varying levels of prostaglandin concentrations are observed depending on how close the process is to spontaneous parturition at term.
• The research indicates that once labor is triggered via this proinflammatory endocrine cascade, it becomes challenging to stop the active labor process by administering drugs aimed at reducing prostaglandin concentrations in the blood.

Future Directions

• There is a need for more extensive research to fully establish the interconnections between prostaglandin production and other endocrine changes associated with labor. This further study would also aid in gaining deeper insights into both term and preterm parturition in the mare.