Uterine blood flow and uterine arterial, venous and luminal concentrations of oestrogens on days 11, 13 and 15 after oestrus in pregnant and non-pregnant sows.

Concentrations of oestradiol-17 beta and oestrone were measured in the uterine arterial and venous blood of anaesthetized sows on Days 11, 13 or 15 of the oestrous cycle or of pregnancy. Uterine arterial blood flow and the amounts of oestradiol-17 beta and oestrone in uterine flushings were determined in the same animals. In pregnant animals arterial and venous concentrations were significantly different (P less than 0.05) for oestradiol-17 beta on Days 11 and 13 and for oestrone on Day 15. Uterine content of both steroids was consistently greater in pregnant than in non-pregnant animals with a peak on Day 13. Uterine arterial blood increased from Day 11 to 13 of pregnancy then declined (P less than 0.08) by Day 15; no change in uterine blood flow occurred on the corresponding days of the oestrous cycle.