Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: June 12, 1996
Publication Date: N/A
Technical Abstract: Uterine IGF I and II concentrations increase around d 25 of pregnancy in the gilt. Relative levels of endometrial IGF binding protein 2 (IGFBP2) mRNA are increased by d 30 of gestation when uterine capacity becomes a factor in determining litter size. This experiment was investigated whether intrauterine crowding affects levels of endometrial IGFBP2 mRNA in early gestation. Six White crossbred gilts were mated and randomly assigned to b slaughtered at d 25 or 35 of pregnancy. On d 4 of pregnancy, gilts were anesthetized and their reproductive tracts surgically exteriorized. Corpora lutea (CL) were counted and uterine horn length measured. One uterine horn was ligated to create a crowded (15-20 cm/CL) and roomy (>25 cm/CL) environment. At slaughter, 500 mg of endometrium from each uterine environment was stored at -80 C until RNA extraction. A uterine section was fixed for in situ hybridization. Steady state levels of IGFBP2 mRNA were quantitated by slot blot analysis. Steady state levels of IGFBP2 mRNA increased (P<.05) from d 25 to 35 in both crowded (7.05 +/- 35.2 vs 134.08 +/- 35.2 pg/5 ug RNA) and roomy (2.97 +/- 35.2 vs 57.16 +/- 35.2 pg/5 ug RNA) environments. Levels of endometrial IGFBP2 mRNA at d 35 of gestation were increased (P<.05) in crowded as compared to roomy environments. Ligand blot analysis indicated that IGFBP2 protein levels tended to increase from d 25 to 35 for crowded [0.95 +/- 1.3 vs 3.60 +/- 1.3 densitometric area (DA)] and roomy environments (1.82 +/- 1.3 vs 2.68 +/- 1.3 DA). In situ hybridization demonstrated that at both d 25 and 35, IGFBP2 mRNA is localized exclusively in the luminal epithelium. Results indicated that endometrial IGFBP2 mRNA expression increases between d 25 and 35 and may be further increased by intrauterine crowding.