Morphometry of the renal corpuscle during postnatal growth and compensatory hypertrophy

Morphometry was used to measure the growth changes in renal corpuscle and glomerular size and composition in outer, middle, and inner cortical layers during postnatal development in normal and mononephrectomized rats. Glomerular growth was 4.16-fold in normal rats and 6.12-fold after nephrectomy. The cell populations in glomeruli showed distinctly different growth patterns. Cellular hypertrophy and hyperplasia during normal growth were 2.72 and 1.52 for epithelial cells, 0.93 and 3.70 for endothelial cells, and 1.28 and 2.65 for mesangial cells; corresponding values during stimulated growth were 2.75 and 1.92, 1.19 and 4.11, and 1.65 and 3.09. A linear transcortical gradient of corpuscle diameters was found in young animals and normal adults, with the mean volume of juxtamedullary renal corpuscles two times greater than that of subcapsular corpuscles in all animal groups. Despite their size variation, a striking transcortical uniformity was evident in the composition of glomeruli in each group with respect to the volume fractions and mean cell volume in each cell population, the volume and surface density of basement membrane, the volume and length density of capillary loops, the volume fraction of mesangial matrix, and the division of basement membrane into peripheral and axial portions.