Morphogenesis and ultrastructure of the peripolar cells in the mouse kidney.

Peripolar cells are located in the outer layer of the Bowman's capsule. They surround the vascular pole of the renal corpuscle and project into the urinary space. Morphologically they are characterized by the presence of secretory granules within their cytoplasm. In order to study their embryological development, we used 60 C57bl mice embryos (15th to 19th gestational day), 10 newborn mice (2 hours to 6 days old), 10 preadult mice (8-30 days old) and 4 adults (4 months old). Some granular cells, dispersed at the outer and inner layer of the Bowman's capsule, appear on the 17th gestational day. Later, these cells are found around the vascular pole of the renal corpuscle, located exclusively at the outer layer of the Bowman's capsule. Their granules are spherical and variously dense, they are surrounded by a membrane and their number increases progressively with time and reaches a maximum on the 4th postnatal day. Following that, there is a diminution and then their population stabilizes. By the end of the first month, there are only a few such cells (mean number 1 to 2). They become smaller and they always project into the urinary space.