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(−) deprenyl induces activities of both superoxide dismutase and catalase but not of glutathione peroxidase in the striatum of young male rats
Life Sciences, Vol. 48, pp. 517-521 Printed in the U.S.A.
Pergamon Press
(-) DEPRENYL INDUCES ACTIVITIES OF BOTH SUPEROXIDE DISMUTASE AND CATALASE BUT NOT OF GLUTATHIONE PEROXIDASE IN THE STRIATUM OF YOUNG MALE RATS M.-C. Carrillo , S. Kanai, M. Nokubo and K. Kitani Department of Clinical Physiology, Tokyo Metropolitan Institute of Gerontology, 35-2, Sakaecho, Itabashi-ku. Tokyo, JAPAN. *(Present address) Instituto De Fisiologia Experimental, Suipacha 570, 2000 Rosario, Universidad Nacional De Rosario, Republica Argentina. (Received in final form November 29, 1990) Summary Daily s.c. injection of (-)deprenyl (2.0 mg/kg/day) for three weeks in young male rats caused a threefold increase in superoxide dismutase (SOD) activity in the striatum of the brain compared with the value in saline-injected control rats. Furthermore, the activity of catalase (but not of glutathione peroxidase) was also increased significantly by deprenyl treatment. The results confirmed the previous findings of Knoll (i) on SOD activity and furthermore provided evidence that the activity of catalase is also significantly induced by the drug, which was not found in the previous study (i). (-)Deprenyl was originally developed for the treatment of Parkinson's disease (2) and its efficacy has been recently confirmed (3). It has been reported retrospectively that patients treated with levodopa plus deprenyl lived longer than patients treated with levodopa only (4). Furthermore, recent animal studies have reported a dramatic prolongation of the life span of male rats that received long-term deprenyl administration (1,5). Knoll suggested that the specific induction of superoxide dismutase (SOD) activity in the striatum observed in rats treated with deprenyl may be causally related to the life prolongation effect of this drug (i). While he observed a tenfold increase in SOD activity in the striatum in deprenyl-treated rats, the activities of catalase and glutathione peroxidase (GSH Px) did not significantly increase, although the activities were generally higher in deprenyl-treated rats. The radical scavenging effect of SOD should be effective only when it is followed by activities of catalase or GSH Px since SOD generates, hydrogen peroxide which is more toxic than oxygen radicals. The studies by Knoll (I) and Knoll, Dallo and Yen (5) have great potential in terms of the mechanisms of aging as well as the possibility of pharmacological intervention in natural life span since no trial to prolong the animal life span by pharmaceuticals has ever been successful. However, the article which desribed the enzyme activities in deprenyl-treated rats lacked clear and detailed information on enzyme assays as well as on the animals used (i). In the present paper, we examined enzyme activity changes by deprenyl treatment in detail. The results confirmed the finding of Knoll (I) that deprenyl induces SOD activity in the striatum of the rat brain. Furthermore, we found a significant increase in the activity of catalase but not of GSH Px. **Address for correspondence. 0024-3205/91 $3.00 +.00 Copyright (c) 1991 Pergamon Press plc
518
Deprenyl Effect on SOD and Catalase
Vol. 48, No. 6, 1991
Materials and methods Chemicals Hydrogen peroxide, xanthine, hydroxyammonium, sulfanilic acid, ~-naphthylamine, potassium cyanide, reduced glutathione (GSH) and sodium azide were obtained from Wako Pure Chemicals Ltd. (Tokyo). Xanthine oxidase, GSH reductase and SOD were from Sigma. NADPH was purchased from Oriental Yeast Co. Ltd. (Tokyo). Animals and treatment Six-month-old Fisher-344 (F-344) rats of the male sex were used for this study. They were randomly divided into two goups. (-)Deprenyl was a generous gift of Fujimoto Pharmaceutical Co. Ltd. (Osaka, Japan). The preparation was dissolved in saline (4 mg/ml). Control rats received a daily s.c. administration of isovolumetric saline solution for 3 weeks. Treated rats received a daily s.c. administration of (-)deprenyl (2 mg/kg/day) during the same period of time. Twenty four h after the last injection, animals were decapitated and the brain immediately excised. Striatum tissues were separated on an ice-cold surface. Tissues were homogenized in 1 ml of distilled cold water. The homogenates were sonicated for 15 sec in a Sonifier B-12 (Branson Sonic). The homogenates were then centrifuged for 2 min in an Eppendorf centrifuge (i0000 x ~). An aliquot of the supernatant was used immediately for the determination of catalase activity, and the remaining supernatant was stored at -20°C until the determination of SOD and GSH Px activities. This was performed within 24 to 48 hr after the preparation of samples. Enzyme assays Catalase. Catalase activity was assayed by the method described by Beers and Sizer (6) in which the disappearance of peroxide is followed spectrophotometrically at 240 nm. The incubation mixture contained 0.05 M potassium phosphate, pH 7.0, 0.020 M hydrogen peroxide and a sample (0.05 ml) of the supernatant fluid, in a final volume of 3 ml. The decrease in absorbance was recorded at 240 nm for 2 min. The rate of decrease in absorbance per min was ca]culate~ from the initial linear portion of the curve (45 sec). The value of 0.0394 cm~/~mol proposed by Nelson and Kiesow (7) was used as the extinction coefficient of H202. One unit of catalase was defined as the amount of enzyme which decomposed one ~mol of H202 per minute at 25°C and pH 7.0 under the specified conditions. Superoxide dismutase (SOD) The activity of SOD was assayed by the method of Elstner and Henpel (8) which is based on the inhibition of nitrite formation from hydroxylammonium in the presence of O2-generators. Nitrite formation from hydroxylammonium chloride was determined under the following conditions. The incubation mixture (2 ml total volume) consisted of phosphate buffer pH 7.8 (65 mM, 1 ml), xanthine oxidase (40 Bg prot, 0.3 ml), xanthine (1.5 ~mol, 0.i ml), and hydroxylammonium chloride (I ~mol. 0.1ml). The reaction was started by the addition of xanthine oxidase and was conducted at 25°C in a water bath for 20 min. The determination of nitrite as a product of hydroxylammonium chloride was assessed in a 0.5 ml sample of the above reaction mixture with sulfanilic (0.01 raM) acid and ~-naphthylamine (0.001 raM) (total volume, 1.5 ml). The optical density of the mixture was determined at 530 nm. Addition of SOD (or 0.015 ml of supernatant) to the incubation mixture yielded an inhibition of nitrite formation. A curve of activity units vs. percentage of inhibition was recorded with known amounts of purified SOD from Sigma Chem. Co., which contained 3600 ~nits/mg protein as assayed by the method of McCord and Fridorich ( 9 ) . Approximately one-fifth of the activity unit yielded a 50% inhibition of hydroxylammonium chloride oxidation. The amount of SOD activity units of the samples was calculated using this curve.
Vol. 48, No. 6, 1991
Deprenyl Effect on SOD and Catalase
519
Differentiation between the two different types of SOD (Cu Znz~OD and MnSOD) was performed by the addition of potassium cyanide (5 X i0-~ M) at the incubation medium. Cu Zu-SOD was inhibited by potassium cyanide, while Mn-SOD was not affected by its presence. Glutathione peroxidase (GSH Px). The GSH Px activity was measured by a modification of the procedure described by Paglia and Valentine (I0). The standard assay mixture (3 ml) contained: 0.I M buffer phosphate pH 7, 1 mM GSH, 0.2 mM NADPH, 1.4 IU GSH-reductase, 0.25 raM H^O^ or 1.2 mM cumene hydroperoxide, and a z sample (0.04 ml) of supernatant fluid. Hydrogen peroxide was used as a substrate, and I mM sodium azide was added to the reaction mixture in order to inhibit possible remnant catalase activity after the freezing of the samples. Blank values obtained without the addition of samples were subtracted from the assay values. The use of two substrates permitted the measurement of two isozymes: a selenium-dependent GSH Px (Se-GSH Px) which reacts with a wide variety of hydroperoxides including both hydrogen peroxide and organic hydroperoxides, and a nonselenium-dependent GSH Px (non Se-GSH Px), which does not use hydrogen peroxide as a substrate but reacts with organic hydroperoxides. Statistical analysis. All values were expressed as mean + SD. The difference between control and deprenyl-treated rats was analyzed by Student's t test for unpaired values. P values lower than 0.05 were judged to be significant. Results "fABLE I shows the summary of enzyme activity measurements in striatum tissues from saline-treated (control) and deprenyl-treated rats. The amount of SOD activity was three times greater in deprenyl-treated rats than in control rats. The difference was highly significant. A significant increase was observed in both Cu Zn-SOD and Mn-SOD activities. The catalase activity was also significantly higher (by 60 ~) ~n deprenyl-treated rats. In contrast, the GSH Px activity did not differ significantly between the two groups. TABLE I Enzyme Activities in the Striatum of the Brain of Male F-344 Rats Saline treated rats (n=6) Body weight (g) Weight of striatum (mg) Protein concn. ~n striatum (mg/g) SOD (U/mg prot.) Cu Zn-SOD Mn-SOD
(-)Deprenyl treated rats (n=6)
321.5 + 13.0
318.6 + 15.5
44.0 ~ 2.0
47.6 ~ 3.0
156 + 16
144 + 24
3.32 + 1.87 0.336 ~ 0.145
, 9.47 + 3.69 , 0.913 ~ 0.300
Catalase (U/mg)
8.50 + 1.98
14.4 + 3.21
GSH Px (mU/mg) Se-GSH Px non Se-GSH Px
42.3 + 4.0 25.2 ~ 7.4
42.1 + 7.0 27.0 ~ 3.8
*Significantly different from respective control values (P
520
Deprenyl Effect on SOD and Catalase
Vol. 48, No. 6, 1991
DISCUSSION In a previous study (I), Knoll reported that deprenyl treatment for 3 weeks resulted in a significant increase in SOD activity in the striatum in both male and female rats, in a dose-dependent manner. Unfortunately, this report lacked detailed information on enzyme activity measurement as well as on the rats used (age, strain, etc.). The present study confirmed, however, that this drug, when administered for 3 weeks, significantly increases the SOD activity in the striatum of young male F-344 rats. The magnitude of increase (threefold) is lower than that the maximally induced value (a tenfold increase in comparison to the control value) reported by Knoll (I), but the increase was highly significant. The increase was confirmed to occur with both of the two species of SOD (Cu Zn-SOD and Mn-SOD), which was not documented in the original report of Knoll ( i ) . The dosage used in the present study is the highest dose Knoll used. Knoll, however, could not find a significant increase in catalase activity, although it tended to be higher in deprenyl-treated rats (i). In contrast, the 60% increase in catalase activity induced by deprenyl treatment in the present study was statistically significant. In the study of Knoll (I), the activity of GSH Px was also higher in deprenyl-treated rats, although the difference did not gain a statistical significance. In contrast, in the present study, GSH Px activities were almost identical in deprenyl-treated and control rats for Se dependent as well as in Se dependent enzyme activities. Since SOD generates hydrogen peroxide, which is biologically more toxic than oxygen radicals, a concomitant increase in cstalase (or GSH Px) activity is essential if we expect a beneficial effect from the increase in SOD activity. The observation made in the present study, therefore, indicates that deprenyl treatment may be effective in preventing the free radical induced tissue damage in the striatum, if such a damage increases during aging of animals. Although many studies have suggested the possibility of tissue damage caused by radicals during aging, evidence is still indirect and largely based on the presence of TBA reactive substances. In future studies, direct measurements of superoxide radicals or the immediate products of lipid peroxidation are needed to validate such a thesis. The causal relationship between the increase in these enzyme activities in the striatum and the life prolongation reported previously (1,5) remains to be established. Knoll speculated that the toxic metabolites of monoamines generated in the striatum may deteriorate the function of the nigro-striatum system, which is an efficient regulatory mechanism of animal life span according to him (I). The crucial point on this issue is how specific the role of the nigrostriatum is in regulating the life span of animals. In this regard we recently confirmed that there was no change in enzyme activities in hippocampus in rats treated with deprenyl as was originally reported by Knoll (i) (Carrillo et al., unpublished observation). We also need to examine whether other major antioxidant sources such as those in the liver are modulated by this drug. Studies are also in progress in this laboratory to clarify these important points. Furthermore, before we discuss the causal relationship between effects of deprenyl on enzyme activities in the striatum and the life span of animals, we first of all need to confirm the observation of Knoll (1,5) on the life prolongation. A recent study from another group (II) also reported a significant prolongation of the life span of male F-344 rats, but the effect was less dramatic than was originally reported by Knoll (1,5). We are also in the process of examining the effect of (-)deprenyl on the life span of rats and mice. Acknowledgements This study was supported by a grant in aid "Pharmacodynamics (1987-1991) in the Tokyo Metropolitan Institute of Gerontology.
of the brain"
Vol. 48, No. 6, 1991
Deprenyl Effect on SOD and Catalase
521
The authors deeply appreciate Dr. G.O. Ivy for having provided valuable information on deprenyl which prompted us to initiate the present study. The skilful secretarial work of Mrs. T. Ohara is also gratefully appreciated. References i. 2. 3. 4. 5. 6. 7. 8. 9. 10. ii.
J. KNOLL, Mech. Ageing Dev. 46 237-262 (1988). J. KNOLL, Acta Neurol. Scand. Suppl. 95 57-80 (1983). Parkinson Study Group, N. Eng. J. Med. 321 1364-1771 (1989). W. BIRGMAYER, J. KNOLL, P. RIEDER, M.B.H. VOUDIN, V. HARS and J. MARTON, J. Neur. Transm. 64 113-127 (1985). J. KNOLL, J. DALLO and T.J. YEN, Life Sci. 45 525-531 (1989). R.F. BEERS, Jr. and I.W. SIZER, J. Biol. Chem. 195 133 (1952). D.P. NELSON and L.A. KIESOW, Anal. Biochem. 49 474 (1972). E.F. ELSTNER and A. HEUPEL, Anal. Biochem. 70 616 (1976). J.M. MCCORD and I.FRIDOVICK, J. Biol. Chem. 244 6049 (1969). D.E. PAGLIA and W.N. VALENTINE, J. Lab. Clin. Med. 70 158 (1967). N.W. MILGRAM, R.J. RACINE, P. NELLIS, A. MENDONCA and G.O. IVY, Life Sci. 47 415-420 (1990).
Pergamon Press
(-) DEPRENYL INDUCES ACTIVITIES OF BOTH SUPEROXIDE DISMUTASE AND CATALASE BUT NOT OF GLUTATHIONE PEROXIDASE IN THE STRIATUM OF YOUNG MALE RATS M.-C. Carrillo , S. Kanai, M. Nokubo and K. Kitani Department of Clinical Physiology, Tokyo Metropolitan Institute of Gerontology, 35-2, Sakaecho, Itabashi-ku. Tokyo, JAPAN. *(Present address) Instituto De Fisiologia Experimental, Suipacha 570, 2000 Rosario, Universidad Nacional De Rosario, Republica Argentina. (Received in final form November 29, 1990) Summary Daily s.c. injection of (-)deprenyl (2.0 mg/kg/day) for three weeks in young male rats caused a threefold increase in superoxide dismutase (SOD) activity in the striatum of the brain compared with the value in saline-injected control rats. Furthermore, the activity of catalase (but not of glutathione peroxidase) was also increased significantly by deprenyl treatment. The results confirmed the previous findings of Knoll (i) on SOD activity and furthermore provided evidence that the activity of catalase is also significantly induced by the drug, which was not found in the previous study (i). (-)Deprenyl was originally developed for the treatment of Parkinson's disease (2) and its efficacy has been recently confirmed (3). It has been reported retrospectively that patients treated with levodopa plus deprenyl lived longer than patients treated with levodopa only (4). Furthermore, recent animal studies have reported a dramatic prolongation of the life span of male rats that received long-term deprenyl administration (1,5). Knoll suggested that the specific induction of superoxide dismutase (SOD) activity in the striatum observed in rats treated with deprenyl may be causally related to the life prolongation effect of this drug (i). While he observed a tenfold increase in SOD activity in the striatum in deprenyl-treated rats, the activities of catalase and glutathione peroxidase (GSH Px) did not significantly increase, although the activities were generally higher in deprenyl-treated rats. The radical scavenging effect of SOD should be effective only when it is followed by activities of catalase or GSH Px since SOD generates, hydrogen peroxide which is more toxic than oxygen radicals. The studies by Knoll (I) and Knoll, Dallo and Yen (5) have great potential in terms of the mechanisms of aging as well as the possibility of pharmacological intervention in natural life span since no trial to prolong the animal life span by pharmaceuticals has ever been successful. However, the article which desribed the enzyme activities in deprenyl-treated rats lacked clear and detailed information on enzyme assays as well as on the animals used (i). In the present paper, we examined enzyme activity changes by deprenyl treatment in detail. The results confirmed the finding of Knoll (I) that deprenyl induces SOD activity in the striatum of the rat brain. Furthermore, we found a significant increase in the activity of catalase but not of GSH Px. **Address for correspondence. 0024-3205/91 $3.00 +.00 Copyright (c) 1991 Pergamon Press plc
518
Deprenyl Effect on SOD and Catalase
Vol. 48, No. 6, 1991
Materials and methods Chemicals Hydrogen peroxide, xanthine, hydroxyammonium, sulfanilic acid, ~-naphthylamine, potassium cyanide, reduced glutathione (GSH) and sodium azide were obtained from Wako Pure Chemicals Ltd. (Tokyo). Xanthine oxidase, GSH reductase and SOD were from Sigma. NADPH was purchased from Oriental Yeast Co. Ltd. (Tokyo). Animals and treatment Six-month-old Fisher-344 (F-344) rats of the male sex were used for this study. They were randomly divided into two goups. (-)Deprenyl was a generous gift of Fujimoto Pharmaceutical Co. Ltd. (Osaka, Japan). The preparation was dissolved in saline (4 mg/ml). Control rats received a daily s.c. administration of isovolumetric saline solution for 3 weeks. Treated rats received a daily s.c. administration of (-)deprenyl (2 mg/kg/day) during the same period of time. Twenty four h after the last injection, animals were decapitated and the brain immediately excised. Striatum tissues were separated on an ice-cold surface. Tissues were homogenized in 1 ml of distilled cold water. The homogenates were sonicated for 15 sec in a Sonifier B-12 (Branson Sonic). The homogenates were then centrifuged for 2 min in an Eppendorf centrifuge (i0000 x ~). An aliquot of the supernatant was used immediately for the determination of catalase activity, and the remaining supernatant was stored at -20°C until the determination of SOD and GSH Px activities. This was performed within 24 to 48 hr after the preparation of samples. Enzyme assays Catalase. Catalase activity was assayed by the method described by Beers and Sizer (6) in which the disappearance of peroxide is followed spectrophotometrically at 240 nm. The incubation mixture contained 0.05 M potassium phosphate, pH 7.0, 0.020 M hydrogen peroxide and a sample (0.05 ml) of the supernatant fluid, in a final volume of 3 ml. The decrease in absorbance was recorded at 240 nm for 2 min. The rate of decrease in absorbance per min was ca]culate~ from the initial linear portion of the curve (45 sec). The value of 0.0394 cm~/~mol proposed by Nelson and Kiesow (7) was used as the extinction coefficient of H202. One unit of catalase was defined as the amount of enzyme which decomposed one ~mol of H202 per minute at 25°C and pH 7.0 under the specified conditions. Superoxide dismutase (SOD) The activity of SOD was assayed by the method of Elstner and Henpel (8) which is based on the inhibition of nitrite formation from hydroxylammonium in the presence of O2-generators. Nitrite formation from hydroxylammonium chloride was determined under the following conditions. The incubation mixture (2 ml total volume) consisted of phosphate buffer pH 7.8 (65 mM, 1 ml), xanthine oxidase (40 Bg prot, 0.3 ml), xanthine (1.5 ~mol, 0.i ml), and hydroxylammonium chloride (I ~mol. 0.1ml). The reaction was started by the addition of xanthine oxidase and was conducted at 25°C in a water bath for 20 min. The determination of nitrite as a product of hydroxylammonium chloride was assessed in a 0.5 ml sample of the above reaction mixture with sulfanilic (0.01 raM) acid and ~-naphthylamine (0.001 raM) (total volume, 1.5 ml). The optical density of the mixture was determined at 530 nm. Addition of SOD (or 0.015 ml of supernatant) to the incubation mixture yielded an inhibition of nitrite formation. A curve of activity units vs. percentage of inhibition was recorded with known amounts of purified SOD from Sigma Chem. Co., which contained 3600 ~nits/mg protein as assayed by the method of McCord and Fridorich ( 9 ) . Approximately one-fifth of the activity unit yielded a 50% inhibition of hydroxylammonium chloride oxidation. The amount of SOD activity units of the samples was calculated using this curve.
Vol. 48, No. 6, 1991
Deprenyl Effect on SOD and Catalase
519
Differentiation between the two different types of SOD (Cu Znz~OD and MnSOD) was performed by the addition of potassium cyanide (5 X i0-~ M) at the incubation medium. Cu Zu-SOD was inhibited by potassium cyanide, while Mn-SOD was not affected by its presence. Glutathione peroxidase (GSH Px). The GSH Px activity was measured by a modification of the procedure described by Paglia and Valentine (I0). The standard assay mixture (3 ml) contained: 0.I M buffer phosphate pH 7, 1 mM GSH, 0.2 mM NADPH, 1.4 IU GSH-reductase, 0.25 raM H^O^ or 1.2 mM cumene hydroperoxide, and a z sample (0.04 ml) of supernatant fluid. Hydrogen peroxide was used as a substrate, and I mM sodium azide was added to the reaction mixture in order to inhibit possible remnant catalase activity after the freezing of the samples. Blank values obtained without the addition of samples were subtracted from the assay values. The use of two substrates permitted the measurement of two isozymes: a selenium-dependent GSH Px (Se-GSH Px) which reacts with a wide variety of hydroperoxides including both hydrogen peroxide and organic hydroperoxides, and a nonselenium-dependent GSH Px (non Se-GSH Px), which does not use hydrogen peroxide as a substrate but reacts with organic hydroperoxides. Statistical analysis. All values were expressed as mean + SD. The difference between control and deprenyl-treated rats was analyzed by Student's t test for unpaired values. P values lower than 0.05 were judged to be significant. Results "fABLE I shows the summary of enzyme activity measurements in striatum tissues from saline-treated (control) and deprenyl-treated rats. The amount of SOD activity was three times greater in deprenyl-treated rats than in control rats. The difference was highly significant. A significant increase was observed in both Cu Zn-SOD and Mn-SOD activities. The catalase activity was also significantly higher (by 60 ~) ~n deprenyl-treated rats. In contrast, the GSH Px activity did not differ significantly between the two groups. TABLE I Enzyme Activities in the Striatum of the Brain of Male F-344 Rats Saline treated rats (n=6) Body weight (g) Weight of striatum (mg) Protein concn. ~n striatum (mg/g) SOD (U/mg prot.) Cu Zn-SOD Mn-SOD
(-)Deprenyl treated rats (n=6)
321.5 + 13.0
318.6 + 15.5
44.0 ~ 2.0
47.6 ~ 3.0
156 + 16
144 + 24
3.32 + 1.87 0.336 ~ 0.145
, 9.47 + 3.69 , 0.913 ~ 0.300
Catalase (U/mg)
8.50 + 1.98
14.4 + 3.21
GSH Px (mU/mg) Se-GSH Px non Se-GSH Px
42.3 + 4.0 25.2 ~ 7.4
42.1 + 7.0 27.0 ~ 3.8
*Significantly different from respective control values (P
520
Deprenyl Effect on SOD and Catalase
Vol. 48, No. 6, 1991
DISCUSSION In a previous study (I), Knoll reported that deprenyl treatment for 3 weeks resulted in a significant increase in SOD activity in the striatum in both male and female rats, in a dose-dependent manner. Unfortunately, this report lacked detailed information on enzyme activity measurement as well as on the rats used (age, strain, etc.). The present study confirmed, however, that this drug, when administered for 3 weeks, significantly increases the SOD activity in the striatum of young male F-344 rats. The magnitude of increase (threefold) is lower than that the maximally induced value (a tenfold increase in comparison to the control value) reported by Knoll (I), but the increase was highly significant. The increase was confirmed to occur with both of the two species of SOD (Cu Zn-SOD and Mn-SOD), which was not documented in the original report of Knoll ( i ) . The dosage used in the present study is the highest dose Knoll used. Knoll, however, could not find a significant increase in catalase activity, although it tended to be higher in deprenyl-treated rats (i). In contrast, the 60% increase in catalase activity induced by deprenyl treatment in the present study was statistically significant. In the study of Knoll (I), the activity of GSH Px was also higher in deprenyl-treated rats, although the difference did not gain a statistical significance. In contrast, in the present study, GSH Px activities were almost identical in deprenyl-treated and control rats for Se dependent as well as in Se dependent enzyme activities. Since SOD generates hydrogen peroxide, which is biologically more toxic than oxygen radicals, a concomitant increase in cstalase (or GSH Px) activity is essential if we expect a beneficial effect from the increase in SOD activity. The observation made in the present study, therefore, indicates that deprenyl treatment may be effective in preventing the free radical induced tissue damage in the striatum, if such a damage increases during aging of animals. Although many studies have suggested the possibility of tissue damage caused by radicals during aging, evidence is still indirect and largely based on the presence of TBA reactive substances. In future studies, direct measurements of superoxide radicals or the immediate products of lipid peroxidation are needed to validate such a thesis. The causal relationship between the increase in these enzyme activities in the striatum and the life prolongation reported previously (1,5) remains to be established. Knoll speculated that the toxic metabolites of monoamines generated in the striatum may deteriorate the function of the nigro-striatum system, which is an efficient regulatory mechanism of animal life span according to him (I). The crucial point on this issue is how specific the role of the nigrostriatum is in regulating the life span of animals. In this regard we recently confirmed that there was no change in enzyme activities in hippocampus in rats treated with deprenyl as was originally reported by Knoll (i) (Carrillo et al., unpublished observation). We also need to examine whether other major antioxidant sources such as those in the liver are modulated by this drug. Studies are also in progress in this laboratory to clarify these important points. Furthermore, before we discuss the causal relationship between effects of deprenyl on enzyme activities in the striatum and the life span of animals, we first of all need to confirm the observation of Knoll (1,5) on the life prolongation. A recent study from another group (II) also reported a significant prolongation of the life span of male F-344 rats, but the effect was less dramatic than was originally reported by Knoll (1,5). We are also in the process of examining the effect of (-)deprenyl on the life span of rats and mice. Acknowledgements This study was supported by a grant in aid "Pharmacodynamics (1987-1991) in the Tokyo Metropolitan Institute of Gerontology.
of the brain"
Vol. 48, No. 6, 1991
Deprenyl Effect on SOD and Catalase
521
The authors deeply appreciate Dr. G.O. Ivy for having provided valuable information on deprenyl which prompted us to initiate the present study. The skilful secretarial work of Mrs. T. Ohara is also gratefully appreciated. References i. 2. 3. 4. 5. 6. 7. 8. 9. 10. ii.
J. KNOLL, Mech. Ageing Dev. 46 237-262 (1988). J. KNOLL, Acta Neurol. Scand. Suppl. 95 57-80 (1983). Parkinson Study Group, N. Eng. J. Med. 321 1364-1771 (1989). W. BIRGMAYER, J. KNOLL, P. RIEDER, M.B.H. VOUDIN, V. HARS and J. MARTON, J. Neur. Transm. 64 113-127 (1985). J. KNOLL, J. DALLO and T.J. YEN, Life Sci. 45 525-531 (1989). R.F. BEERS, Jr. and I.W. SIZER, J. Biol. Chem. 195 133 (1952). D.P. NELSON and L.A. KIESOW, Anal. Biochem. 49 474 (1972). E.F. ELSTNER and A. HEUPEL, Anal. Biochem. 70 616 (1976). J.M. MCCORD and I.FRIDOVICK, J. Biol. Chem. 244 6049 (1969). D.E. PAGLIA and W.N. VALENTINE, J. Lab. Clin. Med. 70 158 (1967). N.W. MILGRAM, R.J. RACINE, P. NELLIS, A. MENDONCA and G.O. IVY, Life Sci. 47 415-420 (1990).