Dynamics of Follicular Blood Flow, Antrum Growth, and Angiogenic Mediators in Mares From Deviation to Ovulation

This study aimed to investigate dynamics of dominant and subordinate follicles' change of dimensions, vascularity, and angiogenic hormones from deviation to ovulation. Ten cyclic mares were subjected to daily blood sampling and Doppler examination along two estrous cycles. Three diameters were recorded for each follicle to estimate its area and volume. Leptin, insulin-like growth factor-I (IGF-1), nitric oxide (NO) and estradiol were measured. Area of color and power Doppler modes with antral area and circumference of all follicles was measured in pixels. Follicles were classified into first large preovulatory follicle (1st F-ov), second large (2nd F-ov), and third large (3rd F-ov) on the ovulating ovary and on the contralateral nonovulating ovary into first (1st F-contra) and second large (2nd F-contra). Days before ovulation significantly (P < .0001) affected all dimensions of preovulatory follicle. With the increase of diameter, area, volume, area in pixel, antrum area, and circumference of 1st F-ov, those of all subordinates were decreasing. The blue flow area, power, and power minus red blood flow area of 1st F-ov increased from day −6 till day of ovulation (day 0), but red blood flow area significantly decreased. First large follicle had the lowest percent of colored pixels and percent of the colored pixels without antrum. Estradiol and leptin increased from day −6 till day 0, but IGF-1 decreased till day −1 and NO achieved a peak on day −3 then decreased till day 0. In conclusion, antrum growth, blood flow, and angiogenic hormones play a role in maturation and ovulation of the dominant follicle in mares.