Insulin-like growth factor-binding protein-2: the effect of human chorionic gonadotropin on its gene regulation and protein secretion and its biological effects in rat Leydig cells.
Human CG (hCG) and insulin-like growth factor-I (IGF-I) have synergistic effects on Leydig cell function. Leydig cells express high affinity IGF-I receptors. The number of IGF-I receptors and IGF-I receptor mRNA levels can be up-regulated by hCG. The most abundant mRNA species of the IGF binding proteins (IGFBPs) in rat Leydig cells is IGFBP-2. In the present study, we investigated the effect of hCG on IGFBP-2 transcription, mRNA accumulation, and protein production/secretion. Biological effects of IGFBP-2 on Leydig cells were also examined. Rat Leydig cells were purified from testes using centrifugal elutriation followed by Percoll gradient centrifugation. Cells were cultured for 24 h and then treated with or without hCG (10 ng/ml) for 6 h. The expression of IGFBP-2 mRNA was decreased by hCG in a dose-dependent manner, and at a concentration of 10 ng/ml the expression of IGFBP-2 mRNA was reduced by 50%. As early as 2 h after the addition of hCG, there was a significant decrease in IGFBP-2 mRNA accumulation. To evaluate the mechanism(s) responsible for decreased IGFBP-2 gene expression by hCG, the effect of hCG on the rate of transcription and stability of the mRNA was determined. Human CG (10 ng/ml) reduced the IGFBP-2 transcription rate by 32%/h in comparison with the control, while the half-life (t1/2) of mRNA remained unaltered (hCG-treated cells, 0.58 h; control cells, 0.51 h). IGFBP-2 with a molecular size of 33 kilodaltons was detected as a major band in the Western ligand blot.(ABSTRACT TRUNCATED AT 250 WORDS)
Wang
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Medical Services, W. J. B. Dorn Veterans Hospital Columbia, South Carolina 29201.
Nagpal
M L
ML
Lin
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Shimasaki
S
S
Ling
N
N
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007985:Leydig Cells / Q000187:drug effects* / Q000502:physiology; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000494:pharmacology; D013739:Testosterone / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects
D002352:Carrier Proteins; D006063:Chorionic Gonadotropin; D018971:Insulin-Like Growth Factor Binding Protein 2; D012333:RNA, Messenger; D011994:Recombinant Proteins; D013739:Testosterone; D007334:Insulin-Like Growth Factor I