Plasma and endometrial progesterone content following exogenous progesterone administration in mares.

The research explores the effects of administering two different types of progesterone to both whole and surgically-altered mares, noting that there was no significant differences in their bodies’ progesterone levels afterwards. The two treatments also stimulated the growth of the endometrial gland in a similar manner.

Introduction and methodology

• This study investigated the physiological responses of mares (female horses) to two different types of exogenous (externally applied) progesterone: progesterone in-oil and repositol progesterone.
• The research subjects were mares which were both intact and ovariectomized (surgeries were performed to remove their ovaries). The effects of the progesterone treatments were evaluated by examining serum progesterone, endometrial progesterone, and endometrial histology (the study of structure of the endometrium under the microscope).

Results on progesterone levels

• The study found that there were no significant differences in serum progesterone levels (progesterone in the blood) or tissue progesterone levels (progesterone in the endometrium tissue of the uterus) between the intact and ovariectomized mares.
• Moreover, both types of mares treated with progesterone in-oil showed higher serum and tissue progesterone levels compared to those treated with repositol progesterone. This result suggests that progesterone in-oil might be absorbed more efficiently in mares, which leads to elevated progesterone levels in both blood and tissue.

Effects on endometrial gland proliferation

• In addition to measuring progesterone levels, the researchers also observed the effects of progesterone treatments on endometrial gland proliferation (the growth and multiplication of endometrial glands).
• Both progesterone in-oil and repositol progesterone treatments initiated the proliferation of endometrial glands. Furthermore, there was no significant difference observed in terms of gland proliferation response between the two types of progesterone treatments.

Conclusions

• The research findings suggested that the type of mare (whether intact or ovariectomized) does not affect the horse’s physiological response to exogenous progesterone treatments.
• While progesterone in-oil seems to be more effective in raising the progesterone levels in mares, both types of progesterone can stimulate the endometrial gland proliferation equally.