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Project Number: WVA00129 EMBRYOTOXIC EFFECT OF EARLY REGRESSION OF FIRST CORPUS LUTEUM IN POSTPARTUM ANESTRUS IN BEEF COWS Investigators: Inskeep, E.K.,
Lewis, P.E. Termination Date: 09/30/1998 Termination Report: Early luteal regression in cattle has an embryotoxic effect not overcome by replacement with progesterone, but prevented by removal of the regressing CL. Two experiments tested whether the embryotoxic effect is delivered by a systemic pathway. Recipient 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; Exp. 1) or 5 (n = 9; Exp. 2) through 8; controls (n = 19) received saline. Progestogen replacement therapy (12 mg flurogestone acetate daily, sc) was provided from Day 6 (Exp. 1) or 4 (Exp. 2) until ultrasonographic diagnosis of embryo survival on Day 35 after estrus. 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 significantly with location (adjacent or opposite to the regressing CL) or location by treatment interaction. Survival of embryos did not differ significantly with location (adjacent or opposite to the regressing CL) or with location by treatment interaction. Thus embryo mortality associated with luteolytic effects of PGF2alpha in cows receiving replacement therapy with progestogen involves compounds acting systemically or transported via the uterine lumen after local transfer from the ovary to the adjacent uterine horn. To attempt to identify the factor(s) involved, cows (n = 15) received either PGF2alpha (15 mg in 3 ml of saline) or saline (3 ml) intramuscularly every 8 h, beginning on d 4 after synchronized estrus. CL were removed at 24 (n = 2) or 48 (n = 2) h after initiation of saline, or 24 (n = 4), 48 (n = 4), or 72 (n = 3) h after initiation of PGF2alpha. Total RNA was harvested after treatment with PGF2alpha and subjected to reverse transcription polymerase chain reaction (RT-PCR), first with random primers and then using primers specific for insulin-like growth factor binding protein 1 (IGFBP-1) and b-actin to evaluate expression of these genes. Experssion of IGFBP-1 was increased at 24 and 48 h after beginning treatment with PGF2alpha, then returned to control values by 72 h. In contrast, b-actin expression did not change during luteal regression. These findings have been used as the basis for further work under Hatch Project 321 and for a grant proposal. Two papers have been submitted for publication. Publications: Hernandez-Fonseca, H.J., B.L. Sayre, R.L. Butcher, and E.K. Inskeep. 1999. Systemic embryotoxic effect of early regression of the bovine corpus luteum. Thereiogenology: Submitted. Hernandez-Fonseca, H.J. 1998. Systemic versus local embryotoxic effect of the early regressing corpus luteum in the cow. M.S. Thesis, West Virginia University, Morgantown. Sayre, B.L., R. Taft, E.K. Inskeep, and J. Killefer. 1999. Changes in gente expression during regression of the early bovine corpus luteum: Increased expression of IGF binding protein-1. Biol. Reprod.: Submitted. Taft, R., B.L. Sayre, E.K. Inskeep, and J. Killefer. 1999. IGF binding protein-1 is increased during prostaglandin F2alpha-induced regression of bovine corpora lutea. J. Reprod. Fertil. Supp. 54:In press (Abstract).
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