Amylobarbitone hydroxylation kinetics in small samples of rat and human liver

1. Two micro methods for determining amylobarbitone hydroxylase activity from less than 3 mg liver are described. One is based on single-ion monitoring g.l.c.-mass spectrometry and the other on t.l.c. separation of 14C-labelled product. 2. Km and Vmax have been determined with rat liver and both needle and open biopsy samples of human liver. 3. Both methods are sufficiently sensitive and reproducible for use with 20 mg needle biopsies.