Table 4. EC50 values (nM) for IR activation and relative activation compared to IR-B.

Receptor	Insulin EC50 (nM) Geometric mean (95% confidence intervals)	IGF1 EC50 (nM) Geometric mean (95% confidence intervals)	IGF2 EC50 (nM) Geometric mean (95% confidence intervals)
IR-A	1.3 (0.4 to 4.1)	37 (11 to 123)	5.0 (4.5 to 5.6)
IR-A P718K	1.3 (0.4 to 4.2)	97 (53 to 177)*	23 (10 to 50)*
IR-B	1.8 (0.7 to 4.8)	308 (154 to 613)	32 (10 to 104)
IR-B K718P	1.7 (0.8 to 3.4)	68 (14 to 340)*	8.0 (5.2 to 12.1)*

IR activation measured as total tyrosine phosphorylation in ELISA assay for IR-A, IR-B, IR-A P718K and IR-B K718P. The geometric mean of EC50 (nM) and the 95% confidence intervals are given for n = 3 independent experiments.

*) Significant difference (p < 0.05) determined by T-test between WT and mutant.