Intracellular Localization of Carbonic Anhydrase in the Frog Nephron

Abstract

The study was possible by sectioning tissue embedded in plastic (Sorwall, JB-4), before staining essentially according to Hansson. This procedure preserved the intracellular structure well and the resolution is high. For light microscopy sections from 1-10 .mu.m were used. For EM 0.25 .mu.m thick sections were stained and examined using an accelerating voltage of 100 kV. The highest concentrations of the enzyme were localized in cell membranes of their immediate neighborhood. A faint cytoplasmic staining was sometimes observed. In distal tubule cells the apical part of the cell membrane was heavily stained. Weaker staining was found at the lateral membranes and their infoldings and to some extent the basal parts of the cell membrane. In the canaliculi cells only the lateral and basal parts of the membranes were stained. This latter localization was similar to that in the parietal cells of the mammalian stomach.