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)[1]References
- 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. Wang, D., Nagpal, M.L., Lin, T., Shimasaki, S., Ling, N. Mol. Endocrinol. (1994) [Pubmed]
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