RESUMO
Objective To describe quantitatively the development of the capillary loop stage glomerulus (capG) with respect to the volume density of capillaries in the glomerulus based on the morphogenesis of the kidney. Methods The kidneys were obtained from mice at various developing time points and prepared for paraffin sections. The volume density of CD34 positive endothelial cells and surrounded capillary lumen in glomeruli was measured using a combination of immunohistochemical staining and the stereological grid system. Results The capG was divided into early, middle, and late phases, and middle phase capG was subdivided into early-middle and late-middle phases, according to the morphology of developing glomeruli and the arrangement of podocytes. As result, the volume density of capillary loops in early phase capG could not be measured due to the complex "glomerular" shape. The volume density of capillary loops increased from (35.95±6.45)% in the early-middle phase capG, to (58.36±6. 30) % in the late-middle phase capG, and to (79.89± 5.21) % in the late phase capG, compared to (93.61 ±1.96) % in the mature glomerulus. Furthermore, the volume density of capillary loops remained constant at same stage even though at different developmental time points. Conclusion This study demonstrated a significantly increased volume density of capillary loops with the kidney development. In addition, the results provide a descriptive and reliable parameter for the evaluation of glomerular development.