Capillary growth in overloaded, hypertrophic adult rat skeletal muscle: An ultrastructural study

摘要: We examined the early stages of angiogenesis in overloaded m. extensor digitorum longus following extirpation agonist tibialis anterior. Capillary-to-fibre ratio increased after 1 week (1.54 ± 0.02) vs. control (1.38 0.06; P < 0.01) and resulted a greater tortuosity capillary bed at 2 weeks, indicating presence lateral sprouts or anastomoses. Capillary endothelial cells (ECs) showed ultrastructural signs activation, were thickened, had irregular luminal abluminal surfaces. The proportion ECs with processes overload (13.5 0.6% 2.0 1.5%, contralateral, 0.01; 12.5 2.6% 3.5 0.6%, weeks 0.01), whereas there was no significant change processes. Abluminal occurred approximately 13% capillaries muscles (P 0.01 v. contralateral), most associated focal breakage basement membrane (BM). Small (<3 μm diameter) comprised one two sometimes lacked lumen, others slitlike vacuolelike lumen between adjacent formed by fusion vesicles within single EC. Endothelial mitosis occasionally seen nonsprouting intact BM, increasing average number per from 1.7 to 2.1 0.05) when bromodeoxyuridine incorporation also higher 0.001). conclude that muscle induces growth sprouting existing capillaries, probably due mechanical stretch acting side vessels. Anat. Rec. 252:49–63, 1998. © 1998 Wiley-Liss, Inc.