R. L. Butcher

Prostaglandin F2α in the uterus of ewes during early pregnancy

Abstract PGF 2α has been postulated to be the uterine luteolytic factor. If this is true, then one might expect the levels of PGF 2α to be lower during early pregnancy. However, in the present study levels of PGF 2α were found to be significantly higher in both content (ng) and concentration (ng/gm) in the endometrium of day-13 pregnant ewes (2375, 152 respectively) compared to day-13 nonpregnant animals (1478, 89 respectively). These results imply that the luteotropic effects of the embryo must occur by some mechanism other than inhibition of production or release of the uterine luteolytic factor.

Effects of breed, age of donor and dosage of follicle stimulating hormone on the superovulatory response of beef cows

Data were obtained on 1039 recoveries of embryos from beef cows of four breeds at two locations, in clinic and on farm. General linear models procedures were utilized to determine the effects of breed, location, age of donor, dosage of follicle stimulating hormone (FSH) and the interaction of age and FSH on the following dependent variables: 1) the mean number of ova (unfertilized oocytes and embryos) recovered; 2) the mean number and percentage of embryos (fertilized; live and dead) recovered; and 3) the mean number and percentage of transferable embryos recovered. The interaction of age of donor and dosage of FSH with breed and location prevented the pooling of data over breed and location. The mean number of ova recovered was affected by age of the donor (Charolais-in clinic), or the interaction between age of donor and dosage of FSH (Polled Hereford-in clinic and -on farm and Simmental -on farm). The mean number of embryos was affected by age of donor (Polled Hereford-in clinic), dosage of FSH (Simmental-in clinic) or their interaction (Angus-on farm). The mean number of transferable embryos was affected by age of donor (Polled Hereford-in clinic and -on farm, Simmental-in clinic and Angus-on farm). General linear models procedures were utilized to determine the effects of the embryo (stage of development and quality) and the recipient (synchrony with the donor) on the rate of pregnancy. Rate of pregnancy varied with embryo quality score and synchrony of the recipient and the embryo. In conclusion, the superovulatory response was found to be highly breed-specific, and most of the variability in embryos produced was attributed to the number of ova recovered. However, the number of ova, embryos and transferable embryos recovered was further influenced by age of the donor, dosage of FSH or their interaction.

Effects of progesterone on endometrial prostaglandins in sheep

The effects of progesterone on endometrial levels of prostaglandins were investigated in intact and ovariectomized ewes. In the first experiment 17 ewes were ovariectomized bilaterally on day 4 of the estrous cycle. Eight ewes served as controls and 9 ewes received 10 mg progesterone on days 4 through 8. All ewes were killed on day 9. The concentration (ng/g) and content (ng/uterus) of PGF2α were lower (P<.05) in the progesterone-treated ewes (18 and 204, respectively) compared to the controls (64 and 575, respectively). In the second experiment, 20 intact ewes received 40 mg progesterone in corn oil and 20 intact ewes received corn oil only on days 0 and 1 of the estrous cycle. Ten ewes in each group were killed on day 5 and ten on day 9. A significant increase (P<.05) in PGF2α content, but not concentration, was detected due to progesterone treatment. PGF2α did not vary with day or the interaction of day with progesterone treatment. No differences in PGF1α content or concentration were detected in either experiment. The results suggest that progesterone, by itself, is not responsible for the previously reported increase in levels of prostaglandin in the endometrium of ewes at day 14 of the estrous cycle. The luteolytic effect of progesterone given early in the estrous cycle could result in part from increased levels of PGF2α.

Embryotoxic effects adjacent and opposite to the early regressing bovine corpus luteum.

Early luteal regression in cattle has an embryotoxic effect that is not overcome by replacement with progesterone, but is prevented by removal of the regressing CL. Two experiments were designed to test the null hypothesis that the luteal component of the embryotoxic effect is delivered by a systemic pathway. Beef heifers and cows (n = 39) received two good quality embryos, one placed into each uterine horn on Day 6 or 7 of the estrous cycle. Treated animals (n = 20) received 15 mg of PGF2alpha three times per day from Day 7 (n = 11; Experiment 1) or 5 (n = 9; Experiment 2) through 8; controls (n = 19) received saline. Progestogen replacement therapy (12 mg flurogestone acetate daily, s.c.) was provided from Day 6 (Experiment 1) or 4 (Experiment 2) until ultrasonographic diagnosis of embryo survival on Day 35 after estrus. The effects of treatment, location of the embryo and location by treatment interaction on embryo survival were tested by Chi square. In Experiment 1, there was no significant difference in embryo survival rate between PGF2alpha-treated and control recipients. In Experiment 2, only 6 of 18 embryos survived to Day 35 when transferred to animals treated with PGF2alpha compared to 12 of 18 in control animals (P< 0.05). The survival of embryos did not differ with location (adjacent or opposite to the regressing CL) or location by treatment interaction. Thus no evidence was obtained to support a local effect of the regressing CL. The embryo mortality associated with luteolytic doses of PGF2alpha in cows receiving replacement therapy with progestogen probably involves compounds that either act systemically or are transported via the uterine lumen to the uterine horn contralateral to the regressing CL.