GSH-independent denitration of organic nitrate esters in rabbit hepatic and vascular cytosol.
The denitration of organic nitrate esters in rabbit hepatic cytosol was characterized. Sephadex G-200 chromatography of ammonium sulfate precipitate (40-80%) from hepatic cytosol demonstrated the presence of two distinct activities (peak I and peak II) responsible for the denitration of nitroglycerin (NTG) and isosorbide dinitrate (ISDN). The denitration of peak I required dithiothreitol (DTT), but not glutathione (GSH), and was not inhibited by S-alkyl GSH, an inhibitor of glutathione S-transferase (GST). Whereas, the denitration activity of peak II was potentiated by GSH, and was inhibited by S-alkyl GSH. These results strongly suggest that the denitration of organic nitrate esters, such as NTG and ISDN, can be catalyzed by at least two enzymes, GSH-independent denitration (peak I) and the GSH-dependent denitration (peak II, GST), in rabbit hepatic cytosol. The denitration activity of peak I was inhibited by SH-modified reagent, indicating that free thiol(s) is (are) critical for expression of the denitration activity. Also, in rabbit vascular cytosol, the cofactor requirement for denitration and response to S-hexyl GSH suggest the participation of GSH-independent enzyme which is responsible for the denitration of organic nitrate esters.
Ogawa
N
N
Drug Metabolism Laboratory, Taisho Pharmaceutical Co., Ltd., Saitama, Japan.
Hirose
T
T
Tsukamoto
M
M
Fukushima
K
K
Suwa
T
T
Satoh
T
T
D000818:Animals; D001808:Blood Vessels / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D005978:Glutathione / Q000502:physiology*; D007548:Isosorbide Dinitrate / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D005996:Nitroglycerin / Q000378:metabolism*; D011817:Rabbits
D005996:Nitroglycerin; D005978:Glutathione; D007548:Isosorbide Dinitrate; D005033:Ethylmaleimide