Measurement of Substrate-induced Oxygen Uptake during Microsomal Drug Oxidation using a Gold Micro-electrode

Abstract

1. A resin-coated gold micro-electrode has been used for polarographic determination of oxygen concentration in liver microsomal suspensions from phenobarbital-pretreated rats.

2. The rate of oxygen uptake on addition of an NADPH-regenerating system and the rate after addition of various substrates of the mixed function oxidase system were measured. The rate of oxygen uptake was faster in the presence of substrate than in the presence of NADPH alone.

3. Kinetic constants (K_m and V_max) for biphenyl, hexobarbital, ethylmorphine, naphthalene and SKF 525-A measured by this technique compare favourably with those obtained either by measurements of NADPH oxidation, or chemical measurements of substrate disappearance or product formation.

4. The practical applications of the gold electrode to drug metabolism studies are discussed.