Estradiol, progesterone and testosterone receptors for pig endometrium and myometrium at various stages of the estrous cycle.

The concentration of unoccupied, occupied and total receptors for estradiol (E2R), unoccupied receptors for testosterone (TR) and progesterone (PsR) in the endometrium (E) and myometrium (M) of cycling gilts or sows after the second or the third farrow were measured. On day O (estrus) the concentration of E2R, TR and PsR reached the maximum for total uterus (M + E). On day 0, there were no differences between concentration of PsR, TR and occupied, unoccupied and total E2R for E and M. In other stages of estrous cycle, the concentration of receptors in E and M were considerably different both in cycling gilts or sows after second or third farrow. On day 13 (luteal phase), high levels of E2R were found but only for E, while there were the lowest level of occupied, unoccupied and total E2R for M. In sows, after the second or third farrow the concentration of E2R in E as well as in M at all stages of the estrous cycle was about three times higher than in cycling young gilts. The concentration of TR in E as well as in M was lowest on day 13, increased on day 17 and reached the highest level at estrous. The concentration of PsR in M was the lowest at luteal phase (day 13), increased on day 17 and reached the highest level at estrus. Significant negative correlation between the concentration of PsR and progesterone in the blood plasma was calculated for M, but not for E.

The lack of relationship between progesterone level in utero-ovarian vein and the number of corpora lutea in the pigs.

Progesterone (P4) level in blood taken from both left and right utero-ovarian vein of cyclic sows was determined and number of corpora lutea in adjacent ovaries was recorded. No relationship between these two parameters has been shown.

Steroid transfer from the ovarian vein to the ovarian artery in the sow.

The ovary and its vascular pedicle were isolated and transferred under a stereomicroscope to a heated surface (40 degrees C). The ovary was supplied with the blood from the middle uterine artery through a cannula. On different days of the oestrous cycle [3H]testosterone, [3H]progesterone or [3H]oestradiol-17 beta were infused for 30 min into the ovarian vein 1--2 cm below the ovary. During and 30 min after the infusion radioactivity was found in ovarian arterial blood and ovarian tissue. Recovery of [3H]testosterone, [3H]oestradiol and [3H]progesterone infused into the ovarian vein from ovarian venous blood collected during 60 min of experiment was (mean +/- s.e.m.) 26.8 +/- 6.8%, 20.1 +/- 6.1% and 23.7 +/- 6.2% respectively. When 51Cr-labelled blood blood cells were infused in the same fashion as the steroids there was no radioactivity in arterial blood or ovarian tissue. These results indicate the existence of a countercurrent transfer mechanism and retention of the hormones in tissue(s) other than blood in the ovarian pedicle.

A subovarian exchange mechanism for the countercurrent transfer of ovarian steroid hormones in the pig.

Sow ovaries with their ovarian pedicle were isolated and supplied with blood from the middle uterine artery. During the 30 min of infusion with [3H]testosterone into the ovarian vein 3 cm below the ovary and for the 30 min after the infusion, radioactivity was detected in tissue fluid 3 cm laterally from the ovarian vein and artery. When [3H]testosterone was infused into the muscles of the ovarian pedicle radioactivity was detected in the ovarian artery branches near the ovary. Of the total amount of blood entering the ovarian artery 63.7 +/- 4.2% reached the ovary and 36.3 +/- 3.1% travelled to the muscles and connective tissue of the ovarian pedicle. It was demonstrated that the ovarian arterial branches supplying the ovarian pedicle muscles after capillarization form the veins which descend within the ovarian artery network, redivide and create the venous mesh covering the spiralling ovarian artery branches. It is suggested that a special subovarian exchanging mechanism exists in the ovarian pedicle for countercurrent transfer of ovarian steroid hormones and that ovarian function can thereby be regulated.

Venous-arterial counter-current transfer of [3H]testosterone in the vascular pedicle of the sow ovary.

[3H]Testosterone or 51Cr-labelled red blood cells were infused for 30 min through a cannula inserted into the ovarian vein below the hilus of the ovary of cyclic sows. The whole of the vascular pedicle was isolated by ligations from the systemic circulation except for the ovarian artery supplying the ovary. During and after the testosterone infusion, radioactivity was found in ovarian arterial blood and ovarian tissue, but not in peripheral blood. When 51Cr-labelled blood cells were infused in the same fashion there was no radioactivity in arterial blood or ovarian tissue. These results indicate the existence of a counter-current transfer for testosterone in the sow ovarian vascular pedicle.