Relationship between intrafollicular concentrations of parathyroid hormone-related peptide (PTHrP) and steroid hormones in oestrogenic and non-oestrogenic ovarian follicles in the mare.

The research studied the relationship between the presence of parathyroid hormone-related peptide (PTHrP) and hormone levels in horse ovarian follicles during different stages of development. The findings suggested a possible role of PTHrP in ovarian function control.

Study Design and Materials

• The study involved harvesting ovaries from 40 Thoroughbred and Thoroughbred Cross mares upon their slaughter within the months of February to May.
• A total of 174 follicles were dissected from these ovaries. Each follicle’s diameter was measured followed by aspiration of the follicular fluid. This fluid was then assayed for PTHrP, oestradiol (E), testosterone (T), and progesterone (P).

Classification of Follicles

• The dissected follicles were classified as either oestrogenic or non-oestrogenic based on the concentration of oestradiol found in their follicular fluid. Follicles with an oestradiol content higher than 40 ng/ml were categorised as oestrogenic, while those with a concentration lower than 40 ng/ml were categorised as non-oestrogenic.

Key Findings

• The study found that the concentration of PTHrP was significantly higher in the follicular fluid of oestrogenic follicles. This suggests that PTHrP might be associated with hormone production during certain stages of follicular development.
• However, the concentrations of testosterone (T) and progesterone (P) did not show any significant difference between the two types of follicles.
• Additionally, the study noted that the ratio of oestradiol to testosterone (E:T ratio) was significantly higher in the follicular fluid of oestrogenic follicles. This again, points towards a possible role for PTHrP in determining follicular state.
• The research also found that the mean diameter of oestrogenic follicles was significantly larger than those categorised as non-oestrogenic, suggesting differences in growth level and development stage between the two types of follicles.

Conclusion

• This research indicates that higher concentration of PTHrP observed in healthy oestrogenic follicles suggests its potential role in the regulation and control of ovarian function. The study’s findings have opened up possibilities for further investigation into the role of PTHrP in the ovarian function of other animal species as well.