Insulin-like growth factor (IGF)-I, IGF-I receptor, and IGF binding protein-3 messenger ribonucleic acids and protein in corpora lutea from prostaglandin F(2alpha)-treated gilts.
Insulin-like growth factor-I (IGF-I) is produced within the porcine corpus luteum (CL) and is thought to play an autocrine/paracrine role in CL development/function during the early luteal phase. This study examines the hypotheses that the luteolytic actions of prostaglandin F(2alpha) (PGF(2alpha)) during the early luteal phase may involve either a decrease in IGF-I or IGF receptor (IGF-IR), or an increase in IGF binding protein (IGFBP)-3, expression, any of which could interfere with the luteotropic actions of IGF-I in this tissue. Cycling gilts were treated twice daily with PGF(2alpha) (or saline) on Days 5-9 of the cycle to induce premature luteolysis. CL were collected on Days 6-9, and RNA, protein, or progesterone was extracted. By slot blot analysis, steady-state levels of IGF-I and IGFBP-3 mRNA were not different in PGF(2alpha)-treated vs. control animals; however, IGF-IR mRNA was increased in treated animals on Day 9. No changes in IGF-I content (ng/CL measured by RIA) were observed with respect to treatment. According to ligand blot analysis, the levels of IGFBP-3 increased on Day 6 and decreased on Days 8-9, while IGFBP-2 was higher on Days 6-7 and decreased on Day 9 in treated animals. IGF-IR levels, determined from Western blots, were higher on Day 7 (P < 0.05) and lower on Day 9 in PGF(2alpha)-treated animals vs. control animals (P < 0.05). In conclusion, PGF(2alpha)-induced premature luteolysis was associated with an increase in steady-state levels of IGF-IR mRNA, but it did not appear to be linked to changes in mRNA levels for IGF-I or IGFBP-3. However, since IGFBP-2 and -3 protein levels increased early in the treatment period (Days 6-7), it is possible that they may mediate the luteolytic actions of PGF(2alpha) by sequestering IGF-I and preventing its interaction with the IGF-IR.
Nicholson
W C
WC
Department of Anatomy, Physiological Sciences and Radiology, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina 27695, USA.
Ge
Z
Z
Plotner
D M
DM
Farin
C E
CE
Gadsby
J E
JE
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D003338:Corpus Luteum / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D015237:Dinoprost / Q000494:pharmacology*; D005260:Female; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000378:metabolism; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics / Q000378:metabolism*; D018969:Insulin-Like Growth Factor Binding Proteins / Q000032:analysis; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D009929:Organ Size; D011374:Progesterone / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000235:genetics / Q000378:metabolism*; D013552:Swine / Q000378:metabolism*
D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D011374:Progesterone; D007334:Insulin-Like Growth Factor I; D015237:Dinoprost; D017526:Receptor, IGF Type 1