Effect of diethylstilboestrol on the relationship between LH, PMSG and progesterone during pregnancy in the mare.

This research paper examines the effects of diethylstilboestrol (DES) on the hormonal fluctuations, specifically those concerning luteinizing hormone (LH), pregnant mare serum gonadotropin (PMSG), and progesterone, during a mare’s pregnancy. The findings indicate that DES does not significantly affect these hormonal levels or the duration of gestation.

Overview of the Study

• The research was divided into two separate studies which aimed to establish the relationship between LH and progesterone and between PMSG and progesterone during a mare’s pregnancy.
• In the first study, jugular blood samples were collected daily from 7 mares starting from their first day of heat (oestrus) until the 28th day of pregnancy.
• In the second study, blood samples were collected weekly from 14 mares starting from the 35th day of their gestation, and this continued until they gave birth.

Intervention with DES

• Diethylstilboestrol (DES) is a synthetic estrogen that was administered to approximately half the mares (7 out of 14) in the second study, with the doses ranging from 2 to 10 milligrams.
• The goal of administering DES was to try to extend the secretion of progesterone from the accessory corpora lutea, a hormone that is vital for maintaining pregnancy.
• The other half of mares (the remaining seven) were injected with the vehicle (a substance same as the DES-carrying solution but without DES) which served as the control group.

Results and Conclusion

• When the concentrations of LH, PMSG, and progesterone in the mares’ serum were measured using a radioimmunoassay, it was found that the levels of LH and progesterone were negatively correlated from the start of oestrus until the 4th day of gestation. After that, from days 5 to 28, these hormones were positively correlated.
• The levels of PMSG and progesterone were found to be highly correlated between the 35th and 196th day of gestation, irrespective of whether the mares were injected with DES or the vehicle.
• However, the administration of DES did not have any discernible effect on the serum concentrations of LH, PMSG, or progesterone nor did it affect the length of the gestation period.
• The study thus concluded that DES does not influence the progression or maintenance of pregnancy in mares.