The epithelial cells in the podocytes are polarized in nature with a luminal and basal cell membrane. The cell membrane corresponds to the sole plates of the foot processes. The slit diaphragm is found between the luminal and basal cell membranes (Kriz et al, 1998). A thick surface coat of sialoglycoproteins covers the luminal membrane and the slit diaphragm. The podocytes have a high negative surface charge due to the sialoglycoproteins made up of podocalyxin and podoendin among others. This surface charge helps to maintain the interdigitating pattern of the foot processes. When the surface charge is neutralized by cationic substances like protamine sulphate, the processes draw back and cause tight junctions between them (Kriz et al, 1998). The abluminal membrane contains many proteins participating in the various functions of the glomerulus. Podoplanin is a recently described protein found all over the podocyte. Galatosamine residues of glycoconjugates and A13 (podocyte-specific protein) are found. The cell body has the large nucleus, well developed Golgi system, endoplasmic reticulum and lysosmes (Kriz et al, 1998).Podocytes play a significant role in the physiology and pathology of the glomerulus and form the basis of the filtration process in the kidney along with the slit diaphragm.
The glomerulus has a glomerular filtration barrier which is deeply involved in the kidney functions (Pavenstadt, 2000). The podocyte is the most differentiated cell or highly specialized cell in the glomerulus for the functions. The podocytes stabilize the glomerular architecture by preventing distensions of the glomerular basement membrane and maintain the large filtration surface at the slit diaphragm. They account for 40% of the hydraulic resistance of the filtration barrier (Pavenstadt, 2000). The foot processes are contractile in nature with actin, myosin, alpha-actinin, vinculin and talin and connected to the basement