Figure 5.

Immunoblots demonstrating basal and isoprenaline-stimulated levels of PLB protein phosphorylated at Ser¹⁶ (a) and Thr¹⁷ (b) in perfused hearts of control, diabetic, and insulin-treated diabetic rats. Isolated hearts were perfused with or without 100 nM isoprenaline (ISO) for 5 min, freeze-clamped, and processed to obtain SR-enriched microsomal fractions which were then subjected to Western blot analysis of site-specific phosphorylation of PLB. Original immunoblots (inset). PLB was present as the monomeric form migrating at ∼7 kDa, because the samples were boiled before electrophoresis. Bars represent cumulative data expressed as means±s.e.m. of 3–4 hearts in each group. In each of the experiments, the PLB obtained from control band is normalized as 1.0. ^*P<0.05.