Characteristics of insulin receptors in a clonal line of rat pituitary tumor cells in culture.
The presence of insulin binding sites in a clonal line of cells from rat pituitary tumor (GH1 cells) is described. The binding of insulin was a reversible and specific process. Binding of 125I-insulin to GH1 cells was inhibited by unlabeled insulin and to a minor extent, by proinsulin and desalanine insulin in direct proportion to their biological activities. Trypsin abolished the insulin binding to the cells. Twelve hours incubation of cells with insulin (5 microM) reduced in a 45% of the number of binding sites for the hormone. 125I-insulin bound to GH1 cells dissociated with a t 1/2 of 8 min. At 24 C labeled insulin was degraded by GH1 cells. No degradation was detected at 6 C. Unlabeled insulin inhibited most of the degradation of 125I-insulin, suggesting that degradation resulted from a saturable process. At steady-state, radioactive degradation products as well as 125I-insulin were recovered from GH1 cells.
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002452:Cell Count; D002478:Cells, Cultured; D002850:Chromatography, Gel; D007328:Insulin / Q000378:metabolism; D007457:Iodine Radioisotopes / Q000378:metabolism; D010911:Pituitary Neoplasms / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin / Q000096:biosynthesis*
D007328:Insulin; D007457:Iodine Radioisotopes; D011972:Receptor, Insulin