Abstract

A micromethod for the measurement of aniline hydroxylase activity suitable for small amounts of tissue obtained by needle biopsy of the liver is described. Whole liver homogenate is incubated with ¹⁴C-aniline, after which the incubation mixture is alkalinized, and unreacted aniline is extracted with n-butyl acetate. The residue, which contains the reaction product, p-aminophenol, is counted in a liquid scintillation counter. The reaction is linear to 15 minutes, using 3 to 25 mg of liver tissue. Human aniline hydroxylase activity was found to be lower than that in rats and baboons. Increasing concentrations of phosphate increased aniline hydroxylase activity in the colorimetnic assay for aniline hydroxylase (using 9000 x g supernatant) and in the radioactive assay (with whole homogenate). We also confirmed the increase in enzyme activity produced by pyrophosphate.