Effects of BST on oviductal and uterine genes encoding components of the IGF system in lactating dairy cows.
Lactating Holstein cows, averaging 80 d in milk, were used to examine effects of exogenous bovine somatotropin (bST) on oviductal and uterine genes encoding components of the insulin-like growth factor (IGF) system. About 12 h before expected ovulation in an Ovsynch protocol, cows were assigned randomly to receive bST (500 mg; n = 11) or serve as untreated controls (n = 10). Cows that ovulated (n = 9 bST, 8 control) were divided within treatment to be sacrificed on d 3 or 7 postovulation. Samples of oviductal and intercaruncular endometrial tissue from oviducts and uterine horns ipsilateral to the corpus luteum (CL) were collected and immediately frozen at -80 degrees C for subsequent mRNA analyses. Northern blots revealed mRNAs for IGF-II, IGF-binding protein-2 (IGFBP-2), and IGFBP-3 in all oviductal and endometrial tissues. Significant amounts of IGF-I and growth hormone receptor-1A (GHR-1A) mRNAs were detected in uteri but not in oviducts. The bST treatment had no effect on amount of IGF-I mRNA transcript in uterine endometrium. The mRNA encoding IGF-II was induced by bST in oviducts collected on both d 3 and 7 but was down-regulated in endometrium on d 7. Transcript of IGFBP-2 mRNA was greater in endometrial than oviductal tissues and did not differ between treatments. Both oviductal and endometrial IGFBP-3 mRNA concentrations increased between d 3 and 7 postovulation, with a tendency for greater endometrial IGFBP-3 mRNA in bST-treated cows on d 7. On d 7, concentrations of endometrial GHR-1A mRNA were 30% lower in bST-treated cows. Results indicate complex and tissue-specific regulation of the uterine IGF system components by exogenous bST. Some of those biological responses to bST may be important in early development of bovine embryos.
Pershing
R A
RA
Department of Animal Sciences University of Florida, Gainesville 32611, USA.
Lucy
M C
MC
Thatcher
W W
WW
Badinga
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L
D000818:Animals; D015152:Blotting, Northern; D002417:Cattle / Q000378:metabolism*; D004717:Endometrium / Q000737:chemistry; D030762:Estrous Cycle; D005187:Fallopian Tubes / Q000737:chemistry*; D005260:Female; D015870:Gene Expression / Q000187:drug effects*; D013006:Growth Hormone / Q000494:pharmacology*; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000235:genetics; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics; D007334:Insulin-Like Growth Factor I / Q000235:genetics; D007335:Insulin-Like Growth Factor II / Q000235:genetics; D007774:Lactation; D012333:RNA, Messenger / Q000032:analysis; D011986:Receptors, Somatotropin / Q000235:genetics; D013002:Somatomedins / Q000235:genetics*; D014599:Uterus / Q000737:chemistry*
D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D013002:Somatomedins; C073294:growth hormone, bovine; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D013006:Growth Hormone