= Podocyte
A <podocyte> is a specialized <epithelial cell> covering the outer surface of a glomerular <capillary> within the <renal corpuscle>. It belongs to the visceral portion of the <glomerular capsule>. Its branching extensions end in <podocyte foot process> structures, with a <slit diaphragm> spanning the gaps between neighboring processes. These structures cooperate with the <basement membrane> and capillary <endothelium> in the <glomerular filtration barrier>.
A 1999 experiment located <nephrin> more precisely than ordinary tissue staining could. Antibodies recognized the protein in glomerular extracts, and <immunoelectron microscopy> placed small gold labels in the slits between podocyte processes. The protein was therefore localized to a particular junctional region, rather than uniformly over the cell body.<Nephrin is specifically located at the slit diaphragm of glomerular podocytes by V. Ruotsalainen and others>[Abstract;Figures1–3,antibody tests and immunogold localization]{ref}
This provides an illuminating scale comparison: a light-microscope image can identify a glomerular region, while a molecular label in an electron-microscope section can assign a protein to one component of its filtration surface. Localization supports a structural role but does not, by itself, measure how rapidly <water> or each <solute> crosses the complete barrier.
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