FIGURE 2.

Inhibition of insulin-induced EGFR activation by FFAs. Rat hepatocytes were cultured for 24 h and thereafter stimulated with caprylate or palmitate (50 μmol/liter each), insulin (100 nmol/liter) or a combination of insulin and FFA for up to 60 min. Samples were taken at the indicated time points. Activating EGFR-tyrosine phosphorylation was analyzed by Western blotting using phospho-specific antibodies. Total EGFR served as respective loading control. A, representative immunoblots of three independent experiments. B, values from densitometric analyses of three independent experiments were normalized to the level of total EGFR and expressed as the mean-fold increase over control ± S.E. For the individual time points control was set to 1. Open squares, insulin; closed gray squares, insulin plus C8; closed black squares, insulin plus C16; closed gray triangle, C8; closed black triangle, C16. *, p < 0.05 statistical significance between insulin and insulin plus C8. #, p < 0.05 between insulin and insulin plus C16. EGFR activation at positions Tyr⁸⁴⁵ and Tyr¹¹⁷³ was significantly increased by insulin at each analyzed time point. Insulin plus FFAs significantly increased EGFR phosphorylation within the first 20 min at Tyr⁸⁴⁵ and after 5 min at Tyr¹¹⁷³.