Figure 3. Chronically stimulated IR is refractory to subsequent re-stimulation following removal of insulin.

Insulin receptor tyrosine phosphorylation at (A) pY IR⁹⁷² (170 nM: n = 4 independent studies; 17 nM: n = 5) and (B) pY IR^1162,1163 (170 nM: n = 4; 17 nM: n = 3) quantified by western blot in response to repeated insulin stimulation. (C) total IR protein quantified on the same blots. (D) Total tyrosine (n = 5) and (E) total serine (n = 5) phosphorylation, measured by ELISA (17 nM treatments). Data normalization and symbols are as described in figure 1.