LOCAL INCREASE OF STEROID-HORMONE CONCENTRATIONS IN BLOOD SUPPLYING THE UTERUS AND OVIDUCT IN ANESTHETIZED AND CONSCIOUS GILTS

Sexually mature cycling gilts (n=5) with two recorded oestrous cycles were anaesthetized on Day 10 of the oestrous cycle. On both sides of the uterus, catheters were inserted into branches of the uterine artery proximal to the ovary. The tip of each catheter was placed close to, but above anastomoses with ovarian artery branches. This allowed collection of uterine arterial blood mixed with ovarian arterial blood supplying the uterus and oviduct. A third catheter was placed in the jugular vein. Catheters were exteriorized subcutaneously to the backs of the animals for blood sample collection. Simultaneous blood samples were collected as follows: (a) in anaesthetized animals, every 5 min for 1 h immediately after catheters were inserted during surgery, and every 10 min for 2 h, when the surgery was completed; (b) from conscious animals on Day 2 after surgery, every 10 min for 2 h in the morning and every 10 min for 2 h in the afternoon. Blood plasma samples were assayed for progesterone and androstenedione by RIA method. Mean values (+/- SEM) for progesterone measured in samples collected from branches of the uterine arteries and from the jugular vein in anaesthetized animals were 34 +/- 1.25 ng ml-1 and 26 +/- 1.31 ng ml-1 of plasma, respectively. In conscious animals the measurements showed 33 +/- 0.90 ng ml-1 and 24 +/- 0.81 ng ml-1 of plasma, respectively. Plasma concentration of androstenedione in branches of the uterine arteries and from the jugular vein in anaesthetized and conscious animals were 107 +/- 5.26 pg ml-1 and 72 +/- 5.50 pg ml-1, and 78 +/- 4.54 pg ml-1 and 57 +/- 3.77 pg ml-1, respectively. It was concluded that counter-current transfer of steroid hormones in ovarian pedicle vasculature on Days 10-11 of the oestrous cycle significantly elevates (P<0.0001) the local concentration of steroid hormones in arterial blood supplying the uterus and oviduct (35% for progesterone and 46% for androstenedione).