A, ventricle/body weight in Rab4 transgenic and NTG mice. B, representative cross-sections of hearts stained with hematoxylin and eosin from Rab4 transgenic and NTG mice at 22 weeks of ages. The heart from Rab4 transgenic mouse shows concentric remodeling with thicker left ventricular wall and smaller left ventricular chamber. C, histological analysis of left ventricles stained with Masson’s trichrome from transgenic and NTG mice, showing decreased myocyte number per microscopic field and enlarged myocyte size in Rab4 transgenic mice. D, effect of Rab4 overexpression on the expression of cardiac hypertrophy-associated genes. Representative RNA dot blots from two NTG and two Rab4 transgenic mice are shown (left panel). Total RNA was extracted from ventricles of NTG and transgenic mice. RNA dot blotting was carried out as described under “Experimental Procedures” using 3 μg of RNA per dot. Quantitative data of mRNA expression normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (right panel) are shown. E, echocardiographic analysis of posterior wall thickness of NTG and Rab4 transgenic mouse hearts. F, left ventricular fractional shortening in NTG and Rab4 transgenic mice. Values are the means ± S.E. (n = 7–12; *, p < 0.05 versus NTG).