A SURVEY OF DEHYDROGENASES IN VARIOUS EPITHELIAL CELLS IN THE RAT

Several different epithelial elements that have intense active transport or protein secretory functions were histochemically assayed in several dehydrogenase media by a recently perfected method. The mitochondria represented the only site of activity, not only when tested in the succinate and D-β-hydroxybutyrate media, but also when tested in the lactate, malate, and isocitrate media. The reaction for D-β-hydroxybutyric dehydrogenase in the mouse kidney was curiously limited to the mitochondria of the distal segment of the proximal convoluted tubule, a finding that most convincingly shows that dehydrogenase activity may be differentiated in certain instances from diaphorase activity by the ditetrazole methods and that D-β-hydroxybutyric dehydrogenase is not present in all mitochondria. Tetranitro-BT is favored over nitro-BT in studies conducted on most organs prepared without fixation and on formalin-fixed tissues that consist of lipid-containing or active transport cells.