Shape of cells and intercellular channels in rabbit thick ascending limb of Henle

Electron micrographs of cortical thick ascending limb of Henle (TALH) were studied using morphometric techniques. The apical cell surface and the tubule basement membrane have identical areas of 0.8 x 10(5) mu2/mm of tubule length in a typical tubule (I.D. = 15 mu, O.D. = 25 mu). The total area of lateral cell walls bordering intercellular channels in 7.9 x 10(5) mu2/mm of typical tubule, and the ratio of apical cell surface to lateral surface in 0.10 +/- 0.01. When the photographed tubule mass was divided into five concentric zones of equal thickness, the lateral wall areas per zone were found to increase more rapidly than exponential, from 0.63 x 10(5) mu2/mm in that zone nearest the lumen to 3.6 c 10(5) mu2/mm in that zone adjacent to basement membrane. From these data and the estimated number of cells per mm of tubule length (764 cells), the circumferences of individual cells could be calculated for each zone, and quantative three-dimensional cell model could be constructed. The shape of intercellular channels is similar to that of the space between concentric, truncated, and plated horns. TALH cells are compared to previously described cells of rabbit proximal convoluted and straight tubules.