Effects of luteotrophic and luteolytic hormones on expression of mRNA encoding insulin-like growth factor I and growth hormone receptor in the ovine corpus luteum.
The regulation of mRNAs encoding insulin-like growth factor I (IGF-I) and the receptor for growth hormone (GH-R) in ovine luteal tissue by luteotrophic and luteolytic hormones was examined. In Expt 1, ewes were hypophysectomized (HPX) on day 5 of the oestrous cycle and administered saline (S), LH, GH, or LH + GH until day 12 of the oestrous cycle (n = 4 ewes per group). Concentrations of luteal mRNA encoding IGF-I in HPX + S ewes and pituitary-intact ewes at day 5 (n = 4) were approximately 60% (P < 0.05) of those in pituitary-intact ewes at day 12 (n = 4). Treatment of HPX ewes with GH or GH + LH, but not LH alone, increased concentrations of mRNA encoding IGF-I to values similar to those in pituitary-intact ewes at day 12. Hypophysectomy also reduced the mean concentration of mRNA encoding GH-R to approximately 60% (P < 0.05) of the values in pituitary-intact ewes (days 5 or 12). Treatment with LH, but not GH, increased (P < 0.05) concentrations of mRNA encoding GH-R to values observed in pituitary-intact ewes. In Expt 2, prostaglandin F2 alpha (PGF2 alpha; 1 mumole) injected into the ovarian artery on day 11 or day 12 of the oestrous cycle had no effect on luteal concentrations of mRNA for either IGF-I or GH-R. In Expt 3, concentrations of mRNA encoding IGF-I increased (P < 0.05) between days 3 and 6 and remained high for the duration (days 9, 12 and 15) of the oestrous cycle while luteal concentrations of mRNA encoding GH-R did not change. In conclusion, responsiveness of the corpus luteum to GH and luteal synthesis of IGF-I are likely regulators of luteal development and function. However, PGF2 alpha-induced luteolysis was not associated with a decrease in concentrations of mRNAs encoding either IGF-I or GH-R.
Juengel
J L
JL
Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins 80523-1683, USA.
Nett
T M
TM
Anthony
R V
RV
Niswender
G D
GD
D000818:Animals; D001345:Autoradiography; D015152:Blotting, Northern; D003338:Corpus Luteum / Q000187:drug effects* / Q000378:metabolism; D015237:Dinoprost / Q000494:pharmacology; D004971:Estrus; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D013006:Growth Hormone / Q000494:pharmacology*; D007016:Hypophysectomy; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis / Q000235:genetics*; D016014:Linear Models; D007986:Luteinizing Hormone / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism*; D011986:Receptors, Somatotropin / Q000235:genetics*; D012756:Sheep
D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I; D007986:Luteinizing Hormone; D013006:Growth Hormone; D015237:Dinoprost