The ultrastructure of the developing proximal tubule in the rat kidney

Abstract

The ultrastructure of the proximal tubule cells was studied during development of the nephrons in the newborn and adult rat kidney. Cells in nonfiltering nephrons showed few cellular organelles and a large nucleus. In filtering nephrons the surface area of apical, lateral and basal cell membranes was increased in comparison to nonfiltering nephrons. Those surface areas increased also in filtering nephron as the tubule became more mature. Also the relative volume of mitochondria and the total volume of the cells increased whereas the relative volume of the nucleus decreased. It was also found that the mitochondria were preferentially located closer to the cell membrane as the tubule developed. The observations indicate a close relation between the structural and the known functional development of the rat nephron.