Surface areas of brush border and lateral cell walls in the rabbit proximal nephron

A morphometric technique is used to estimate the absolute and relative surface areas of the brush border microvilli and cell walls bordering lateral intercellular spaces. In isolated, perfused proximal tubule from rabbit, the luminal and lateral surfaces are equal in area. For proximal convoluted tubules (PCT) each surface is 4.1 +/- 0.3 mu2/mu3 of epithelial cell volume or approximately 2.9 X 10(6) mu2/mm of tubule length. In proximal straight tubules (PST) the areas are 2.6 +/- 0.2 mu2/mu3 or 1.2 X 10(6) mu2/mm. Brush border enlarges the apical cell surface 36-fold in PCT and 15-fold in PST. The luminal and lateral cell surfaces each are approximately 20-fold (in PCT) and 10-fold (in PST) greater than the areas of the basal cell surface and tubule basement membrane. These data may be important in the context of an intercellular transport model.