Biotransformation of glyceryl trinitrate by rat brain homogenate

Incubation of glyceryl trinitrate (GTN) with 5% (w/v) rat brain homogenate (RBH) resulted in biotransformation of the organic nitrate vasodilator drug to a mixture of glyceryl-1,2-dinitrate (1,2-GDN) and glyceryl-1,3-dinitrate (1,3-GDN). Heating of the RBH at 100 degrees C for 5 min and (or) pretreatment with 5 mM N-ethylmaleimide at 37 degrees C for 10 min demonstrated that about two-thirds of the GTN biotransformation activity was due to a sulfhydryl-dependent enzymatic process resulting in the predominant formation of 1,2-GDN, and that the remaining biotransformation activity was due to a sulfhydryl-dependent nonenzymatic process resulting in the selective formation of 1,3-GDN. In a preliminary experiment, nitric oxide formation was observed during the incubation of GTN with RBH under anaerobic conditions. These data support the idea that some of the therapeutic and adverse effects of GTN are mediated through its action in the central nervous system.