No abstract

Estradiol (E2), estrone (El), progesterone, LH and prolactin concentrations were determined by radioimmunoassay in blood plasma samples from parous ewes treated with medroxyprogesterone acetate (MAP) or melengestrol acetate (MGA) orally, with MAP by intravaginal sponge, or progesterone by intramuscular injection. Treatment was begun on Day 10 of the estrous cycle and continued for 14 days. Blood samples were collected daily from Day 10 through 13 of the estrous cycle for untreated ewes and from Day 10 through 23 for progestogen-treated ewes, after which the frequency of blood collection was increased to 6-hr intervals until 48 hr after the beginning of estrus.Corpora lutea (CL) regressed, as indicated by a reduction of plasma progesterone concentration, between Day 13 and 15 of the estrous cycle. As soon as the CL regressed, LH (P<.01) and E 2 concentrations increased linearly with time in untreated ewes and in ewes still under treatment with MGA or MAP orally or with progesterone intramuscularly. The increases were not found in ewes treated with MAP

Ovum fertilization after natural mating was inhibited in both oviducts after the insertion of a plastic spiral into one uterine horn. Spermatozoa were found in oviducts of control ewes between 4 and 24 hr after mating, but were almost totally absent from both oviducts of ewes with a spiral in one horn. Sperm numbers in the uterus were relatively low in`s piral' ewes. Spirals had these effects both 2 to 4 weeks and 8 to 10 months after insertion.Ova were fertilized in`s piral' as well as control ewes after injection of semen into the uterus, but there were fewer accessory spermatozoa in ova from`s piral' ewes. After injection of semen into one uterine horn, spermatozoa were found throughout reproductive tracts of`s piral' and control ewes, but most spermatozoa in horns containing a spiral were broken into heads and tails. Similarly, when semen was injected into ligated uterine compartments, most spermatozoa recovered 5 hr later from spiral compartments were tailless; most spermatozoa recovered from non-spiral compartments of the same ewes were intact. Spirals inhibited sperm transport following natural mating, and they also promoted spermicidal conditions in the uterine lumen.

The direction of uterine contractions in vivo was studied in oestrous ewes by recording the motility of exteriorized uteri on cine film. In eight control ewes, 58% of 1156 contractions moved towards the oviduct, while 16% moved towards the cervix. In eight ewes with a plastic spiral in the lumen of one horn, only 17% of 927 contractions moved towards the oviduct; 70% of the contractions moved towards the cervix. The effect of the IUD on the direction of uterine contractions may explain inhibition of sperm transport and ovum fertilization iǹ IUD' ewes.A plastic spiral placed in one uterine horn of the ewe inhibits sperm transport and ovum fertilization (Hawk, 1967). Inhibition of sperm transport is probably not due to suppression of uterine motility because the in vitro motility of strips of myometrium taken from ewes with a spiral in one uterine horn was greater than that of strips taken from control ewes (Brinsfield & Hawk, 1968). Also, attempts to overcome the antifertility effect of the spiral with various compounds which stimulate uterine contractions were unsuccessful (Warren & Hawk, 1968). The possibility remained that a spiral might inhibit sperm trans¬ port by altering some qualitative aspect of uterine motility. The present experiment was conducted to determine whether the presence of a spiral in one uterine horn would alter the direction of uterine contractions in vivo.Sixteen mature, parous ewes were checked twice daily for oestrus by the use of aproned rams. Ewes were laparotomized on Day 10 or 11 of an oestrous cycle (Day of oestrus = Day 0), a small puncture was made in the wall of one uterine horn near its anterior end and a plastic spiral measuring 32 mm in length and 10 mm in diameter was screwed in a posterior direction into the lumen through the puncture so that the spiral lay in the lengthwise centre of the horn. In eight ewes, the spiral was anchored in place by one suture through the uterine wall. The spiral was removed immediately from the remaining eight ewes; these animals served as sham-operated controls. Ewes were assigned to each group at random and the horn to be operated upon within each ewe was also selected at random.At the first oestrus of each ewe that occurred more than 2 weeks after insertion of the spiral, the ewe was anaesthetized with sodium pentobarbital and the uterus was carefully exteriorized through a mid-ventral incision. 535

Acute leucocytic responses to Escherichia coli placed in the uterine lumen were inhibited in oestrous ewes. The response was stimulated in ovariectomized ewes when they were injected with oestradiol, and was inhibited when they were injected with progesterone or with oestradiol and progesterone simultaneously. Uteri of ovariectomized ewes injected with both hormones were similar to those of oestrous ewes, being short and turgid, with high endometrial vascular porosity to circulating vital dye. The results support the suggestion that the inhibition of induced leucocytic emigration in the oestrous sheep uterus may be due to endogenous progestagen.