Three experiments were conducted to examine gene expression during induced luteal regression in the cow; the initial purpose was the identification of potential embryotoxins. In experiment 1, changes in gene expression in the corpus luteum (CL) were identified by differential display reverse transcription–polymerase chain reaction (DD-PCR) during the first 72 h of luteal regression in cows treated with prostaglandin F2α (PGF2α) on Days 4–7 after estrus. Expression of insulin-like growth factor–binding protein-1 (IGFBP-1) was up-regulated, with greatest expression at 24 h (P < 0.05) after treatment with PGF2α began. In experiment. 2, IGFBP-1 and its mRNA were quantified in CL collected 24 or 48 h after treatment with PGF2α on Day 4 or 10 after estrus. Because local mechanisms for exchange of hormones between the ovary and uterus are known in ruminants, uterine flushings were assayed for IGFBP-1 to seek evidence of local transfer of luteal IGFBP-1 to the uterus. IGFBP-1 mRNA was increased (P < 0.05) in CL 24 h after treatment when PGF2α that began on Day 10, and by 48 h after treatment that began on Day 4. Concentrations of IGFBP-1 increased (P < 0.05) in a pattern similar to mRNA, by 24 h on Day 10, and by 48 h on Day 4. Concentrations of IGFBP-1 in uterine flushings did not change on either day. Concentrations of progesterone decreased (P < 0.05) by 8 h after treatment with PGF2α that began on Day 10, but not until 24 h after treatment that began on Day 4. In experiment 3, cows received either saline or PGF2α and CL were collected 2 or 10 h after a single treatment, or 2 h after a second treatment that was given 8 h after the first. Expression of IGFBP-1 was increased by 2 h after treatment with PGF2α on both Days 4 and 10 after estrus. In conclusion, secretion of IGFBP-1 is increased during luteolysis, and may inhibit the steroidogenic effects of insulin-like growth factor-I (IGF-I), but no evidence was found to implicate IGFBP-1 in the embryotoxic effect of regressing CL.
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1 July 2000
Increased Expression of Insulin-Like Growth Factor Binding Protein-1 During Induced Regression of Bovine Corpora Lutea
B. L. Sayre,
R. Taft,
E. K. Inskeep,
J. Killefer
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