Ovarian and uterine haemodynamics during the estrous cycle of Egyptian buffaloes in relation to steroid hormonal and nitric oxide levels

The present investigation aimed to study the ovarian and uterine haemodynamics during the estrous cycle in buffaloes in correlation with the hormonal changes (estradiol and progesterone) and nitric oxide. Six cyclic buffalo cows were scanned via transrectal Doppler ultrasonography to evaluate the normal ovarian and uterine haemodynamics through three successive estrous cycles. Results showed that the dominant follicle (F1) area, F1 diameter, area, antrum area, coloured area (pixels) and colour area % attained the highest values (P<0.0001) during the follicular phase. The vascularisation of F1 tended to be higher (P>0.05) on the day of ovulation (Day 0). The diameter and the vascularisation of the corpus luteum (CL) reached peak values (P<0.0001) at Day 14 and decreased to minimum values at Day 21. Plasma progesterone (P4) concentrations correlated positively with the diameter of CL (r ≤ 0.37; P≤0.01), CL area (r≤0.35; P≤0.009), and CL colour area (pixels) (r≤0.39; P≤0.001). Besides, the estradiol (E2) level correlated with F1 diameter (r≤0.19; P≤0.0001) and F1 area (r≤0.18; P≤0.0001). Peak systolic velocity (PSV) of the ipsilateral ovarian (P≤0.082) and uterine (P≤0.024) arteries were higher than those obtained for the contralateral ones. A similar finding was obtained in end-diastolic velocity (EDV) of the ovarian arteries (P≤0.005). In conclusion, the blood flow of the ovary and uterus recorded in buffaloes varied according to the ovulating ovary, day and phase of the estrous cycle as well as with the hormonal changes.