Discordant Regulation of insulin-like growth factor-II and insulin-like growth factor binding protein-2 gene expression in a rat beta-cell line.

Expression and regulation of IGFBP-2 and IGF-II by GH and glucose in the rat insulin producing beta-cell line, INS-1, were determined. These cells express high levels of the insulin-like growth factor II (IGF-II) gene which is regulated by glucose. GH has no regulatory activities on IGF-II or IGFBP-2 gene expression. The levels of IGF-II and IGFBP-2 mRNA at increasing glucose concentrations are inversely regulated and exogenously added insulin inhibits IGFBP-2 gene expression at low glucose. These observations suggest that the expression of IGFBP-2 gene in this cell line is under the negative control of the endogenously produced insulin (and/or IGF-II) which accumulates to effective levels in the medium when the cells are cultured at high glucose concentrations.