Fig. 4

Light micrographs of peripheral pulmonary arteries and muscularized arteries. a, b, c Peripheral pulmonary arteries. There was no apparent muscle layer in the peripheral pulmonary arteries of normal rats (a). Monocrotaline (MCT)-induced new muscularization of normally non-muscularized arteries (b, c). Arrows b, c denote new muscularization in MCT rats. d, e, f Muscularized arteries with an external diameter of 51–100 μm. g, h, i Muscularized arteries with an external diameter of 101–200 μm. e, f, h, i MCT-induced medial hypertrophy of small muscularized arteries. Medial wall thickness was high in small muscularized arteries with an external diameter of 101–200 μm i in MCT3 rats. Arrows denote the muscle layer. j, k, l The numbers of macrophages and neutrophils in MCT-injected rats were increased in MCT2 (k) and MCT3 (l) rats as compared with the normal group (j). MCT2: rats at 2 weeks after MCT injection; MCT3: rats at 3 weeks after MCT injection