Figure 2.

Tyrosine phosphorylation and protein levels of IRβ in the aorta and microvessels of obese Zucker fa/fa and lean rats ex vivo. Microvessels (a) and aorta (b) were isolated from lean and obese rats as described in Methods, followed by incubation with or without insulin (2–100 nM) in DMEM (0.1% BSA) for 5 minutes (microvessels) or 30 minutes (aorta) at 37°C. Equal amounts of protein (6 mg of microvessel sample and 4 mg of aorta sample) were subjected to immunoprecipitation with αIRβ antibody, separated by SDS-PAGE, and immunoblotted with αPY antibody (top panels). Stripped membranes were reblotted with αIRβ antibody (middle panels). Data (mean ± SD; n = 4) are expressed as relative to control, assigning a value of 100% to the lean control mean. *P < 0.05, lean vs. obese tissues incubated with insulin at the same concentrations.