Uterine luminal content of insulin-like growth factor (IGF)-I and endometrial expression of mRNA encoding IGF-binding proteins 1 and 2 during the oestrous cycle and early pregnancy in the ewe.
Cyclic (n = 30) and pregnant (n = 29) Merino ewes were examined (n = 3 to 5 at most time points) over Days 0-16 and 0-22 after oestrus, respectively. As IGFBP activity was detected in some plasma and ULF samples, all samples were subjected to acid-gel chromatography before assay for IGF-I. After oestrus, the overall means of both groups of ewes showed lower ULF IGF-I content (Days 3 and 12), lower plasma IGF-I concentrations (Days 3-16), higher endometrial expression of mRNA encoding IGFBP-I (Days 12-16) and lower endometrial expression of mRNA encoding IGFBP-2 (Day 8). Between Days 0 and 16 after oestrus, the pregnant ewes had lower plasma IGF-I concentrations and higher endometrial expression of IGFBP-1 mRNA than did the cyclic ewes. The presence of IGF-I in the ULF throughout the oestrous cycle and early pregnancy suggests a role of IGF-I in early pregnancy, influencing both uterine growth and embryonic survival. The concomitant endometrial expression of mRNA encoding IGFBP-1 and IGFBP-2 suggests a role of these binding proteins in the regulation of IGF-I bioavailability in the uterine environment of the ewe.
Cann
C H
CH
Department of Agricultural Sciences, Faculty of Science, Technology and Engineering, La Trobe University, Bundoora, Vic., Australia. nelcan@mcmedia.net.au
Fairclough
R J
RJ
Browne
C A
CA
Gow
C B
CB
D000818:Animals; D004717:Endometrium / Q000378:metabolism*; D004971:Estrus / Q000378:metabolism*; D005260:Female; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000096:biosynthesis* / Q000235:genetics; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000096:biosynthesis* / Q000235:genetics; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D011374:Progesterone / Q000097:blood; D012333:RNA, Messenger / Q000096:biosynthesis; D015203:Reproducibility of Results; D012756:Sheep / Q000378:metabolism*; D014599:Uterus / Q000378:metabolism*
D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D012333:RNA, Messenger; D011374:Progesterone; D007334:Insulin-Like Growth Factor I