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Role of flavo‐enzymes in glyceryl trinitrate biotransformation
Author(s) -
Li Haitao,
Cui Hongmei,
Zweier Jay
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a623-b
Subject(s) - chemistry , nitrite , microsome , biotransformation , biochemistry , enzyme , nitric oxide , cytoplasm , organic chemistry , nitrate
To investigate the magnitude and quantitative importance of flavo‐enzyme‐mediated GTN biotransformation, electron paramagnetic resonance, chemiluminescence nitric oxide (NO) analyzer; and NO electrode studies were performed to characterize magnitude of GTN reduction to nitrite and NO from subcellular fractions of rat liver. Cytoplasm (219.1 mg protein), microsomes (56.0 mg protein), and mitochondria (32 mg protein) were collected by sucrose differential centrifuge from 35 g rat hepatic tissues. Considering the total protein concentration of these compartments, 58.5% nitrite generation, and 37.3% NO generation from GTN (10 uM) are from cytoplasm; microsomal enzymes catalyze 33.2% nitrite generation and 53.7% NO generation; mitochondria enzymatic systems catalyze the 8.2% nitrite and 9.0% NO generation. The presence of the flavo‐enzyme inhibitor diphenyleneiodonium (DPI), 50 uM, inhibits more than 80% of the nitrite generation and 70% of the NO generation from 10 uM GTN in the entire hepatic tissues. Further rat aortic ring isoforce studies show that EC50 values for GTN‐induced relaxation increased from 26 ± 5 nM (control), to 256 ± 45 nM with the presence of 0.2 uM DPI. In conclusion, the primary NO generation (53.7%) from GTN reduction takes place in microsomes; while 58.5% of nitrite generation comes from cytoplasm. The flavin inhibitor studies demonstrate that flavo‐enzymes play critical roles in the process of GTN biotransformation.