Blood flow to the corpus luteum-bearing ovary and ipsilateral uterine horn of cows during the oestrous cycle and early pregnancy.

Total ovarian blood flow of cows (sum of flows through the ovarian artery and uterine branch of the ovarian artery), measured by electromagnetic flow probes, followed a consistent cyclic pattern, being highest from Day 10 of the oestrous cycle (oestrus = Day 0) until 4 days before the subsequent oestrus. During this period of high ovarian blood flow, blood of uterine origin flowed to the ovary through the uterine branch of the ovarian artery and was found to comprise 20-40% of the ovarian blood flow. Between Days -4 and -3, ovarian blood flow dropped (P less than 0.01) from 3.2 +/- 0.5 to 1.0 +/- 0.4 ml/min, coincident with a reversal of flow through this anastomosis. Uterine arterial blood flow was highest (P less than 0.05) from 1 day before oestrous to the day of oestrus when compared to the remaining days of the oestrous cycle. Throughout the oestrous cycle, ovarian blood flow was positively correlated with systemic concentrations of progesterone (r = 0.55, P less than 0.01) and negatively correlated with systemic concentrations of oestradiol-17 beta (r = -0.42, P less than 0.01). In contrast, uterine arterial blood flow was negatively correlated with systemic progesterone (r = -0.25, P less than 0.05) and positively correlated with systemic oestradiol (r = 0.45, P less than 0.05). These data provide direct evidence in the cow that a portion of the blood flowing to the ovary containing a fully functional corpus luteum is contributed by the ipsilateral uterine artery.