SCANNING AND TRANSMISSION ELECTRON-MICROSCOPIC STUDY OF PERIPOLAR CELLS IN THE NEWBORN LAMB KIDNEY

Scanning and transmission electron microscopy were used to study the u ltrastructural characteristics and positions of granulated peripolar c ells in newborn lamb kidney. Following tissue fixation by vascular per fusion in situ, the vascular pole region of the glomerulus was exposed for examination by scanning electron micoscopy following removal of t he glomerular tuft. Peripolar cells were recognized by their surface m orphology enabling their quantification and an assessment of the relat ionship of their position in the renal cortex. The prominent expressio n of peripolar cells in this species was confirmed. Almost every vascu lar pole examined revealed peripolar cells (405 out of 407; 99.5%) and thus, throughout the cortex, the distribution of peripolar cells was the same as the distribution of renal corpuscles. Larger, more protrud ing peripolar cells were observed in the outer cortical renal corpuscl es. The numbers of peripolar cells encircling each vascular pole range d from 1 to 10. There was no correlation between number of granulated peripolar cells at the vascular pole and the position of the renal cor puscle within the renal cortex. As viewed by transmission electron mic roscopy, organelles of protein synthesis were abundant in the cytoplas m of peripolar cells. Exocytosis of cytoplasmic granules was observed by both scanning and transmission electron microscopy implying that a process of regulative secretion occurs from these cells. The use of ul trastructural techniques has provided evidence supporting the concept that peripolar cells are prominent in the cuff region of each renal co rpuscle of the newborn lamb and furthermore that peripolar cells in th is species most likely have a secretory function.