Inability of insulin and insulinlike growth factor-1 to stimulate sugar or amino acid transport and thymidine incorporation in cultured myeloma cells

Abstract

NS-1 mouse plasmacytoma cells were examined for their insulin and insulinlike growth factor-1 (IGF-1) binding characteristics and ability to produce peptide-dependent cellular effects. At concentrations of labelled insulin (i.e., 1.7 × 10−10 M) or IGF-1 (i.e., 1.5 × 10−10 M), NS-1 cells specifically bind 0.2 ± 0.06 fmol insulin per 106 cells (n = 7), where little, if any, IGF-1 specific binding was observed (0.02 ± 0.01 fmol/106 cells) (n = 3). Additionally, the data indicate that the total number of insulin binding sites per cell was 3200 ± 390 (n = 3). Insulin was employed at various concentrations (6.7–667 nM) and failed to stimulate either sugar or amino acid transport. Insulin at low concentrations (i.e., 6.7 or 67 nM) did not stimulate DNA synthesis, yet a small but significant increase was observed at a concentration of 667 nM insulin. IGF-1 did not stimulate DNA synthesis at all concentrations employed (1.4–143 nM). In summary, there exists a small but significant number of insulin receptors, little insulin-stimulated DNA synthesis, and no apparent insulin stimulation of sugar or amino acid transport. Also, since there is no significant IGF-1 binding and no IGF-1 stimulation of DNA synthesis, these findings indicate that this cell line might be a good candidate for the study of insulin receptor function as a transfection recipient of insulin receptor genes.Key words: cultured myeloma cells, insulin and IGF-1 binding and action, sugar transport, amino acid transport, DNA synthesis.