0000000000711610
AUTHOR
Karl J. Netter
Effect of nitrite on microsomal cytochrome P-450.
1. Addition of nitrite to anaerobic rat liver microsomes leads to the appearance of a difference spectrum similar to the spectrum of the ferrous cytochrome P-450-NO complex. A Soret band is found at 444 nm in phenobarbital-stimulated microsomes but at 442 nm in 3-methylcholanthrene-stimulated microsomes. An alpha-band is located at 583 nm in both types of microsome. 2. The initial nitrite-induced difference spectrum is converted into a spectrum lacking a Soret band but with a prominent absorbance minimum at 417 nm. This is more rapid in microsomes from phenobarbital-treated animals where it is completed in 8 min than in microsomes from 3-methylcholanthrene-treated animals. A similar spectru…
Reductive Drug Metabolism in Isolated Perfused Rat Liver under Restricted Oxygen Supply
1. Hepatic azo and nitro reductase activities were studied in the perfused rat liver under normal and restricted oxygen supply. 2. Formation of sulphanilamide or p-aminobenzoic acid from neoprontosil or p-nitrobenzoic acid under aerobic conditions of liver perfusion was negligible, even at a reduced oxygen saturation of a pO2 of 300 mm Hg in the haemoglobinfree perfusion system. At a pO2 of 200 mm Hg reductase activities were almost maximal. 3. Conjugation of sulphanilamide (0-08 mM) was similar under aerobic and anaerobic conditions. Hepatic elimination of p-aminobenzoic acid (0-08 mM) showed an oxygen-dependent increase for 15 min after addition of substrate. 4. p-Nitroanisole demethylati…