Pre-ovulatory follicle affects corpus luteum diameter, blood flow, and progesterone production in mares.

The research investigates the relationship between pre-ovulatory follicle (POF) and corpus luteum (CL) diameter and blood flow with progesterone concentration in mares, highlighting that the POF significantly impacts CL diameter, blood flow, and consequent progesterone production.

Study Design and Procedure

• The researchers applied Color Doppler ultrasonography, an imaging technique that visualizes the flow of blood in the body’s vessels by estimating their speed and direction, to examine the connections between pre-ovulatory follicle (POF) and corpus luteum (CL) size, blood flow, and systemic progesterone (P4) concentration during two transitional ovulatory seasons (spring and fall) in mares.
• To validate these variables, pre-ovulatory follicle and corpus luteum/progesterone were evaluated for 6 days before and 17 days after ovulation, respectively.
• The same evaluations were then conducted on two successive estrous cycles within the spring and fall seasons, and on the final estrous cycle of each respective season.

Findings and Results

• Significant relationships were found among pre-ovulatory follicle and corpus luteum variables, and progesterone concentration, with correlation coefficients ranging from 0.24 to 0.95.
• The study also found significant correlations among the ratios of different variables, which ranged from 0.39 to 0.92.
• Linear regressions, with significance levels ranked from less than 0.01 to 0.001, were present for all comparisons among different variables.
• The researchers observed that the pre-ovulatory follicle diameter prior to the initial ovulation of each season was significantly larger, and its vascularity significantly lesser, than in the concluding estrous cycle of these seasons.
• In contrast, corpus luteum blood flow was significantly lesser during the final pre-ovulatory period compared to the first pre-ovulatory period of the season.
• The sizes of the pre-ovulatory follicles during the two pre-ovulatory periods of spring and fall exhibited a positive correlation, with r=0.67.

Conclusions

• The study provides evidence indicating that the pre-ovulatory follicle influences corpus luteum diameter and blood flow, which subsequently affects progesterone production.
• The researchers also found that pre-ovulatory follicle diameter is persistent within the same individual across different seasons, implying that this variable may serve as a reliable indicator for certain aspects of reproductive health in mares.