Fig. 5.

Hypertrophy of human intestinal muscle cells is induced by synthetic MGF by an Erk-5-dependent mechanism. A: representative images of muscle cell hypertrophy induced by synthetic MGF but cell division induced by rhIGF-I. Hypertrophy was measured in the same groups of cells by confocal imaging of Vybrant CFDA SE cell tracer-loaded cells treated for 4 days with either synthetic MGF (100 nM) or rhIGF-I (100 nM). B: Z-stack analysis showing increased mean cell volume in cells treated with synthetic MGF (100 nM) but not rhIGF-I (100 nM). C: smooth muscle cell hypertrophy induced by synthetic MGF is inhibited by a selective Erk5 inhibitor. Hypertrophy was measured in cells incubated with synthetic MGF (100 nM) for 4 days in the presence or absence of BIX02188 (30 μM) from total cell protein per 10⁴ cells. D: smooth muscle cell proliferation is induced by rhIGF-I but not synthetic MGF. Proliferation was measured by [³H]thymidine incorporation into quiescent muscle cells incubated for 24 h with either synthetic MGF (1–100 nM) or rhIGF-I (1–100 nM). Results are means ± SE of 5–6 separate experiments. *P < 0.05 vs. control.