Figure 8.

C2C12 myoblasts contain a GHR receptor distinct from GHSR-1a. (A) Specific binding (○) was determined by incubation of crude membranes with increasing concentrations of radiolabeled GHR (¹²⁵I-Tyr⁴-GHR) in the absence (total binding, ■) or in the presence (nonspecific binding, ▾) of 1 μM unlabeled GHR. Data are the average of triplicate determinants. Similar results were obtained in at least two other independent experiments. (B) Displacement curves of radiolabeled GHR by unlabeled GHR (○), D-GHR (●), GHR-(9-28) fragment (♦), and motilin (■). Values are the mean ± SEM of three independent experiments. (C) Cells were fixed after 72 h treatment with 10 mM GHR, D-GHR, GHR-(9-28) fragment, and motilin in GM and stained with anti-MHC antibody and DAPI to determine the differentiation index. **p < 0.01 versus control.