Organic nitrate reductase: reassessment of its subcellular localization and tissue distribution and its relationship to the glutathione transferases.

1. Using a specific and sensitive GLC method for the determination of glyceryl trinitrate (GTN), its subcellular and tissue distribution were reassessed. Liver was the most active tissue, but activity was also detected in the heart, kidney and gut. In all tissues activity was localized in the soluble fraction. The activity of soluble glutathione S-transferase followed the same pattern, liver exhibiting the highest and the heart the lowest activity. 2. Pretreatment with phenobarbitone and 3-methylcholanthrene stimulated both the glutathione S-transferase and organic nitrate reductase activities. 3. Glutathione S-transferase activity was competitively inhibited by GTN. 4. A comparison of the plasma and hepatic metabolism of GTN revealed higher drug affinity for the hepatic enzyme.