Insulin action rapidly modulates the apparent affinity of the insulin-like growth factor II receptor

摘要: Incubation of intact rat adipocytes with physiological concentrations insulin stimulates binding insulin-like growth factor II (IGF-II) to its receptor by 3- 10-fold. The effect is temperature- and dose-dependent, 0.1 nM giving half-maximal stimulation. Scatchard analysis IGF-II indicates that this due an apparent increase in affinity, from Kd = 63 the absence 5.8 presence 10 insulin, no change number cell surface sites (220,000/cell). 125I-IGF-II isolated membrane fractions demonstrated all receptors plasma membranes low density microsomes control cells are converted during homogenization high affinity form (Kd 2 6 nM) seen insulin-treated adipocytes. No significant difference was observed between or cells. However, contrast results obtained adipocytes, increased fraction average 60%, while decreased 40% compared These were confirmed direct visualization Mr 270,000 band on dodecyl sulfate gels following labeling cross-linker disuccinimidyl suberate. total cellular showed demonstrate has two effects 1) It rapidly increases without changing surface; 2) it induces a redistribution upon preparation membranes. latter closely parallels insulin-induced glucose transporter occurs adipocyte unknown mechanism.