Effect of active immunization against estrogen on gonadotropin response to testosterone propionate treatment in ovariectomized pony mares.

The research aims to understand if neutralizing some amount of estrogens through active immunization affects the increase in FSH secretion caused by testosterone propionate treatment in female ponies without ovaries. It was found out that immunization against estrogens lowered the testosterone propionate-triggered surge of FSH response by half, indicating that conversion of testosterone to estrogen influences the increase in FSH response to external GnRH in such treated mares.

Experimental Design and Methodology

• The experiment involved using twenty pony mares that had been ovariectomized. The mares were divided into groups as per a 2 X 2 factorial arrangement of treatments with five mares in each group.
• The first factor, referred to as Factor 1, was focused on the mares’ long-term active immunization which was done either against bovine serum albumin (BSA) or estrone-17-oxime-BSA.
• The second factor, Factor 2, was concentrated on the 11-day administration of either a vehicle, which was vegetable oil, or testosterone propionate (TP). The dosage of TP was 175 micrograms/kg BW.

Findings

• The researchers observed no effect (P greater than .1) on the plasma concentrations of FSH from either of the factors.
• As anticipated, the FSH response to the externally administered GnRH was threefold greater in BSA-immunized mares that were treated with TP than those that received oil.
• However, it was noted that the immunization against estrogens reduced the increase in FSH response induced by TP by 52%.
• Further, it was found that TP decreased the plasma concentrations of LH slightly, but immunization against estrogen did not affect this.
• The LH response to the externally administered exogenous GnRH was not affected by either of the factors.

Conclusion

• The research concluded that testosterone’s aromatization to estrogen is partially responsible for promoting the FSH response to exogenous GnRH in mares treated with TP.
• In contrast, suppression of LH concentrations by TP seems to work only through the androgenic impact of TP.