Luteal blood flow and growth in correlation to circulating angiogenic hormones after spontaneous ovulation in mares

Abstract

For evaluating corpus luteum (CL) function, blood flow, circulating nitric oxide (NO), estradiol (E2), progesterone, leptin and insulin like growth factor-I (IGF-1) concentrations were measured for 11 days that were equally divided into early and mid-luteal phases. Five mares underwent blood sampling and rectal Doppler ultrasound examination for 18 days for two estrous cycles. CL diameter, circumference, area and volume increased till day 11. Both blood flow blue area and power area increased from day 1 to 11 but colour blood flow red area declined till day 11. NO concentration increased till day 5 then decreased till day 11. Leptin concentrations declined from day 1 to 11. Power blood flow area and colour blood flow blue area exhibited a significant negative correlation with E2 (r=-0.79;-0.75), leptin (r=-0.73;-0.51), and IGF-1 (r=-0.56;-0.60), but had a positive one with progesterone (r=0.47; 0.52). Days after ovulation and luteal phase affected significantly luteal blood flow and hormone concentrations. The relatively high E2, leptin, IGF-1 and NO during growth compared to static phase indicated a role enhancing angiogenesis and early CL development.