Aim. To study the effect of L-arginine and its analogue N-nitro-L-arginine methyl ester (L-NAME) alone and in combination on lysosomal cysteine proteolysis and lysosomal membranes state in rat aorta.Methods. The study was performed on male Wistar rats kept under standard vivarium conditions and divided into three control and three experimental groups of 8 animals each. The experimental samples included groups with L-arginine and/or L-NAME administration. The indicators were studied in the rat aorta homogenate precipitating and non precipitating fractions. Acid phosphatase activity was determined by a standardized method of «end point», the cathepsins B, L and H activity was studied by spectrofluorimetric method.Results. When simulating the changes of nitric oxide synthesis level using L-arginine, the increase of the total cathepsins activity was detected, acid phosphatase lability coefficient was reduced, what is characterized by general lysosomal membranes stabilization. L-NAME group, in contrast, is characterized by a decrease in the cathepsin B and H activity indicators, differences from arginine group were observed in the cathepsin H in lysosomal and general fractions, lysosomal membrane is labile. Combined drugs administration reduces the total cathepsins activity, while there is an increase of the acid phosphatase total activity, all indicators suggest lysosomal membranes labilization.Conclusion. L-arginine at a dose of 500 mg/kg causes increase in the total cathepsins B, L and H activity in rat aorta due to lysosomal fraction; L-arginine action leads to lysosomal membranes stabilization; L-NAME group in cathepsin H shows a decrease in the cathepsins secretion level with decreased total activity due to both factions; combined administration of arginine + L-NAME group in cathepsin B is characterized by an increase in secretion due to lysosomes membrane labilization.