In Vitro Effects of Sodium Nitroprusside and L-N-Nitroarginine Methyl Ester (L-NAME) on Activity of Lysosomal Cysteine Proteinases and Lysosomal Membrane Permeability.

The direct effect of 5 mM L-NAME and 0.1 mM sodium nitroprusside on activity of lysosomal cysteine proteinases and permeability of lysosomal membrane was studied in vitro after 1, 2, and 4 h of incubation. Isolated from the liver of intact female rats lysosome suspensions were used. Both substances reduced total activity of cathepsin H and did not affect cathepsin B at all time intervals. L-NAME increased cathepsin L activity at all incubation times, while sodium nitroprusside increased activity of this enzyme after 2-h incubation and reduced it incubation after 4-h incubation. L-NAME demonstrated a membrane-destabilizing effect in in vitro experiments, while sodium nitroprusside on the contrary stabilized lysosomal membranes.