Because of advances in ultramicrochemical techniques it is now possible to study the function of the kidney at the level of the nephron. A means for precise identification and dissection of various parts of the nephron in unstained frozen dried sections of tissues obtained by biopsy or autopsy was developed by Bonting and others.1 The validity of these techniques was recently reviewed by Pollak and Mattenheimer.2 In a study of the enzyme activity in the nephron an ultramicrochemical assay technique was used. Photometric determinations of alkaline phosphatase activity, fluorimetric determinations of pyridine-nucleotide-coupled-enzyme reactions and volumetric titrations of glutaminase activity were performed.
In general, enzyme activity was found to be less in the glomeruli than in the convoluted tubules, medullary rays, or outer and inner medullary zones. Acid phosphatase activity was an exception in that it was highest in the glomeruli. Alkaline phosphatase activity was higher in the proximal