Figure 6.

Insulin-induced SIR cleavage by cultured hepatocytes is reduced by the protease inhibitor alpha2-macroglobulin (MG). (A) Microphotographs of representative RHPA assays from control (C), 1 nM insulin-treated hepatocytes, (I), and 1 nmol l⁻¹ insulin-stimulated plus 1.5 mg/ml alpha2-macroglobulin (I + MG). Scale bars: 50 μm. (B) Immunoplaque areas (IPA) as a measure of SIR releasing activity. IPA was calculated after 24 h of incubation in three experiments in duplicate except for MG (n = 2 in duplicate). Bars represent mean ± SEM, **p < 0.01 for comparison against control and ^††p < 0.01 for comparison against 1 nmol l⁻¹ insulin condition. (C) Western blot for SIR of supernatants of hepatocytes cultured in the same conditions of RHPA for 5 days.