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Stephen D. Hall - One of the best experts on this subject based on the ideXlab platform.
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characterization of dextromethorphan n demethylation by human liver microsomes contribution of the cytochrome p450 3a cyp3a subfamily
Biochemical Pharmacology, 1994Co-Authors: Christopher J Gorski, Steven A Wrighton, Stephen D. Hall, David R JonesAbstract:In an effort to identify the human cytochromes P450 involved in the N-demethylation of dextromethorphan, the kinetics of 3-methoxymorphinan formation were studied in microsomal enzyme systems. Under initial rate conditions, 3-methoxymorphinan formation demonstrated single enzyme Michaelis-Menten kinetics using microsomes obtained from three human livers (Km: 0.52–0.71 mM; Vmax: 375–812 pmol/mg protein/min). B-lymphoblastoid cells expressing CYP3A4 incubated with 0.4 mM dextromethorphan catalyzed the formation of 3-methoxymorphinan at a rate of 22 pmol product/mg protein/min. Midazolam, a prototypic substrate for CYP3A4 and CYP3A5, competitively inhibited dextromethorphan N-demethylation by two human liver microsomal samples with Ki values of 46 ± 10 and 63 ± 8 μM. At a dextromethorphan concentration of 0.4 mM, gestodene (100 μM) inhibited 3-methoxymorphinan formation by approximately 50%. Immunoinhibition of dextro-methorphan N-demethylation using rabbit anti-CYP3A4 antibodies resulted in a 60% decrease in 3-methoxymorphinan formation at a dextromethorphan concentration of 0.4 mM. Additional inhibition studies using furafylline, coumarin, sulfaphenazole, mephenytoin, quinidine, and Diethyldithiocarbamic Acid, which are selective inhibitors of CYP1A2, CYP2A6, CYP2C8/9, CYP2Cmp, CYP2D6, and CYP2E1, respectively, demonstrated no substantial inhibition of dextromethorphan N-demethylation. Correlation analysis was performed using the rate of 3-methoxymorphinan formation at a concentration of 1mM dextromethorphan and immunoquantified levels of CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4, and CYP3A5 and their associated characteristic catalytic activities. A significant correlation was observed between dextromethorphan N-demethylase activity and midazolam 1'- and 4-hydroxylase activity (r2 = 0.77 and 0.69 respectively, N = 19, P < 0.01); the exclusion of those samples containing both CYP3A4 and CYP3A5 increased the correlation significantly (r2 = 0.87 and 0.91 respectively, N = 12, P < 0.01). In the absence of CYP3A5, a significant correlation was observed between 3-methoxymorphinan formation and the sample's erythromycin N-demethylase activity (r2= 0.94, N = 12, P < 0.01), testosterone 6 β-hydroxylase activity (r2 = 0.96, N = 7, P < 0.01) and relative immunoquantified levels of CYP3A4 (r2 = 0.96, N = 12, P < 0.01). Inclusion of those samples expressing CYP3A5 in addition to CYP3A4 reduced the magnitude of the observed correlation. No significant correlation between 3-methoxymorphinan formation and the sample's relative immunoquantified levels of or form-selective activity associated with CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19 (or CYP2Cmp), CYP2D6, and CYP2E1 was observed. In conclusion, dextromethorphan N-demethylation appears to be catalyzed primarily by CYP3A4 and to a lesser extent by CYP3A5 in vitro in humans. Thus, the administration of dextromethorphan to human volunteers may provide a means of simultaneously phenotyping the in vivo activity of CYP2D6 and CYP3A.
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characterization of dextromethorphan n demethylation by human liver microsomes contribution of the cytochrome p450 3a cyp3a subfamily
Biochemical Pharmacology, 1994Co-Authors: Christopher J Gorski, Steven A Wrighton, Stephen D. Hall, David R JonesAbstract:In an effort to identify the human cytochromes P450 involved in the N-demethylation of dextromethorphan, the kinetics of 3-methoxymorphinan formation were studied in microsomal enzyme systems. Under initial rate conditions, 3-methoxymorphinan formation demonstrated single enzyme Michaelis-Menten kinetics using microsomes obtained from three human livers (Km: 0.52-0.71 mM; Vmax: 375-812 pmol/mg protein/min). B-lymphoblastoid cells expressing CYP3A4 incubated with 0.4 mM dextromethorphan catalyzed the formation of 3-methoxymorphinan at a rate of 22 pmol product/mg protein/min. Midazolam, a prototypic substrate for CYP3A4 and CYP3A5, competitively inhibited dextromethorphan N-demethylation by two human liver microsomal samples with Ki values of 46 +/- 10 and 63 +/- 8 microM. At a dextromethorphan concentration of 0.4 mM, gestodene (100 microM) inhibited 3-methoxymorphinan formation by approximately 50%. Immunoinhibition of dextromethorphan N-demethylation using rabbit anti-CYP3A4 antibodies resulted in a 60% decrease in 3-methoxymorphinan formation at a dextromethorphan concentration of 0.4 mM. Additional inhibition studies using furafylline, coumarin, sulfaphenazole, mephenytoin, quinidine, and Diethyldithiocarbamic Acid, which are selective inhibitors of CYP1A2, CYP2A6, CYP2C8/9, CYP2Cmp, CYP2D6, and CYP2E1, respectively, demonstrated no substantial inhibition of dextromethorphan N-demethylation. Correlation analysis was performed using the rate of 3-methoxymorphinan formation at a concentration of 1 mM dextromethorphan and immunoquantified levels of CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4, and CYP3A5 and their associated characteristic catalytic activities. A significant correlation was observed between dextromethorphan N-demethylase activity and midazolam 1'- and 4-hydroxylase activity (r2 = 0.77 and 0.69 respectively, N = 19, P < 0.01); the exclusion of those samples containing both CYP3A4 and CYP3A5 increased the correlation significantly (r2 = 0.87 and 0.91 respectively, N = 12, P < 0.01). In the absence of CYP3A5, a significant correlation was observed between 3-methoxymorphinan formation and the sample's erythromycin N-demethylase activity (r2 = 0.94, N = 12, P < 0.01), testosterone 6 beta-hydroxylase activity (r2 = 0.96, N = 7, P < 0.01) and relative immunoquantified levels of CYP3A4 (r2 = 0.96, N = 12, P < 0.01). Inclusion of those samples expressing CYP3A5 in addition to CYP3A4 reduced the magnitude of the observed correlation. No significant correlation between 3-methoxymorphinan formation and the sample's relative immunoquantified levels of or form-selective activity associated with CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19 (or CYP2Cmp), CYP2D6, and CYP2E1 was observed. In conclusion, dextromethorphan N-demethylation appears to be catalyzed primarily by CYP3A4 and to a lesser extent by CYP3A5 in vitro in humans.(ABSTRACT TRUNCATED AT 400 WORDS)
Ergin Şingirik - One of the best experts on this subject based on the ideXlab platform.
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comparative study of the quercetin ascorbic Acid glutathione and superoxide dismutase for nitric oxide protecting effects in mouse gastric fundus
European Journal of Pharmacology, 2013Co-Authors: Peyman Ertug, Ergin Şingirik, Fatma Aydinoglu, Ozlem Goruroglu Ozturk, Nuran OgulenerAbstract:Abstract The aim of this work was to compare the preventing capacity of quercetin with Cu/Zn superoxide dismutase (Cu/Zn SOD), ascorbic Acid and glutathione on nitric oxide (NO)-induced relaxation in mouse gastric fundus. Furthermore, the effects of the quercetin on the tissue level of total oxidant and antioxidant was investigated. Nitrergic stimulation (4 Hz, 25 V, 0.1 ms, 10 s-train) and exogenous NO (10 μM) induced relaxation. Pyrogallol (10 μM), hydroquinone (100 μM) and LY83583 (6-Anilino-quinolin-5,8-quinone, 5 μM) inhibited nitrergic relaxations. The inhibition observed with pyrogallol, hydroquinone and LY83583 was prevented by quercetin (0.1 μM). Also, ascorbic Acid (500 μM), glutathione (100 μM) and Cu/Zn SOD (100 U/ml) prevented the inhibitory effect of superoxide anion generators on the relaxation to nitrergic stimulation and NO. Diethyldithiocarbamic Acid (DETCA; 8 mM) inhibited nitrergic relaxations. DETCA-induced inhibition on nitrergic stimulation and NO-induced relaxation was prevented by quercetin, ascorbic Acid, glutathione or Cu/Zn SOD. DETCA plus pyrogallol, hydroquinone or LY83583 strengthened the inhibition on the relaxations. Also, pre-treatment with quercetin, ascorbic Acid and glutathione prevented the inhibitory effect of DETCA plus LY-83583 on the relaxation to nitrergic stimulation and NO but Cu/Zn SOD did not prevent this inhibition. Also, quercetin increased tissue total antioxidant capacity and decreased tissue oxidant level and oxidative stress index in DETCA-treatment group. These results indicate that quercetin has antioxidant effect and protects NO from endogenous superoxide anion-driven inactivation and enhances its biological activity, suggesting that quercetin may scavenge superoxide anion in a Cu/Zn SOD, glutathione or ascorbic Acid-inhibitable manner.
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protective effect of quercetin a polyphenolic compound on mouse corpus cavernosum
Fundamental & Clinical Pharmacology, 2009Co-Authors: Peyman Ertug, Anil A Olguner, Nuran Ogulener, Ergin ŞingirikAbstract:Flavonoids are plant-based phenolic compounds, and quercetin is the most abundant dietary member of this family. One of the most important characteristics of quercetin is its antioxidant property. The aim of this study was to investigate antioxidant effects of quercetin on corpora cavernosa of mice. Corpora cavernosa were isolated in organ baths, precontracted with phenylephrine (0.5 microm) and relaxant responses were mediated by acetylcholine (0.1-1 microm), electrical field stimulation (EFS, 1-16 Hz, 0.5 ms, 30 V) or Acidified sodium nitrite (a NaNO(2), 0.5 mm). Superoxide anion generators; pyrogallol (50 microm), hydroquinone (100 microm), LY 83583 (6-Anilinoquinolin-5,8-quinone, 10 microm) and superoxide dismutase (SOD) inhibitor; Diethyldithiocarbamic Acid (DETCA, 8 mm) were used in order to expose corpus cavernosa to oxidant stress. Acetylcholine (0.1-1 microm) induced relaxant responses were significantly inhibited in LY 83583 (10 microm) and DETCA + LY 83583 applicated trials. EFS-induced relaxant responses were significantly inhibited in DETCA (8 mm) and DETCA + LY 83583 administrated trials. On the other hand, Acidified sodium nitrite-induced responses were inhibited by all of the superoxide anion generators tested. Quercetin (10 microm) failed to improve the inhibitions on endothelium and electrically stimulated responses. Acidified sodium nitrite (0.5 mm) mediated relaxant responses were significantly restored by quercetin except the groups in which LY 83583 were used. The data suggest that quercetin acts as a protective agent in mouse corpus cavernosum, increasing the bioavailability of exogenous nitric oxide by protecting it from superoxide anion (O(2)(-)).
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protective effect of quercetin a polyphenolic compound on mouse corpus cavernosum
Fundamental & Clinical Pharmacology, 2009Co-Authors: Peyman Ertug, Anil A Olguner, Nuran Ogulener, Ergin ŞingirikAbstract:Flavonoids are plant-based phenolic compounds, and quercetin is the most abundant dietary member of this family. One of the most important characteristics of quercetin is its antioxidant property. The aim of this study was to investigate antioxidant effects of quercetin on corpora cavernosa of mice. Corpora cavernosa were isolated in organ baths, precontracted with phenylephrine (0.5 microm) and relaxant responses were mediated by acetylcholine (0.1-1 microm), electrical field stimulation (EFS, 1-16 Hz, 0.5 ms, 30 V) or Acidified sodium nitrite (a NaNO(2), 0.5 mm). Superoxide anion generators; pyrogallol (50 microm), hydroquinone (100 microm), LY 83583 (6-Anilinoquinolin-5,8-quinone, 10 microm) and superoxide dismutase (SOD) inhibitor; Diethyldithiocarbamic Acid (DETCA, 8 mm) were used in order to expose corpus cavernosa to oxidant stress. Acetylcholine (0.1-1 microm) induced relaxant responses were significantly inhibited in LY 83583 (10 microm) and DETCA + LY 83583 applicated trials. EFS-induced relaxant responses were significantly inhibited in DETCA (8 mm) and DETCA + LY 83583 administrated trials. On the other hand, Acidified sodium nitrite-induced responses were inhibited by all of the superoxide anion generators tested. Quercetin (10 microm) failed to improve the inhibitions on endothelium and electrically stimulated responses. Acidified sodium nitrite (0.5 mm) mediated relaxant responses were significantly restored by quercetin except the groups in which LY 83583 were used. The data suggest that quercetin acts as a protective agent in mouse corpus cavernosum, increasing the bioavailability of exogenous nitric oxide by protecting it from superoxide anion (O(2)(-)).
Peyman Ertug - One of the best experts on this subject based on the ideXlab platform.
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comparative study of the quercetin ascorbic Acid glutathione and superoxide dismutase for nitric oxide protecting effects in mouse gastric fundus
European Journal of Pharmacology, 2013Co-Authors: Peyman Ertug, Ergin Şingirik, Fatma Aydinoglu, Ozlem Goruroglu Ozturk, Nuran OgulenerAbstract:Abstract The aim of this work was to compare the preventing capacity of quercetin with Cu/Zn superoxide dismutase (Cu/Zn SOD), ascorbic Acid and glutathione on nitric oxide (NO)-induced relaxation in mouse gastric fundus. Furthermore, the effects of the quercetin on the tissue level of total oxidant and antioxidant was investigated. Nitrergic stimulation (4 Hz, 25 V, 0.1 ms, 10 s-train) and exogenous NO (10 μM) induced relaxation. Pyrogallol (10 μM), hydroquinone (100 μM) and LY83583 (6-Anilino-quinolin-5,8-quinone, 5 μM) inhibited nitrergic relaxations. The inhibition observed with pyrogallol, hydroquinone and LY83583 was prevented by quercetin (0.1 μM). Also, ascorbic Acid (500 μM), glutathione (100 μM) and Cu/Zn SOD (100 U/ml) prevented the inhibitory effect of superoxide anion generators on the relaxation to nitrergic stimulation and NO. Diethyldithiocarbamic Acid (DETCA; 8 mM) inhibited nitrergic relaxations. DETCA-induced inhibition on nitrergic stimulation and NO-induced relaxation was prevented by quercetin, ascorbic Acid, glutathione or Cu/Zn SOD. DETCA plus pyrogallol, hydroquinone or LY83583 strengthened the inhibition on the relaxations. Also, pre-treatment with quercetin, ascorbic Acid and glutathione prevented the inhibitory effect of DETCA plus LY-83583 on the relaxation to nitrergic stimulation and NO but Cu/Zn SOD did not prevent this inhibition. Also, quercetin increased tissue total antioxidant capacity and decreased tissue oxidant level and oxidative stress index in DETCA-treatment group. These results indicate that quercetin has antioxidant effect and protects NO from endogenous superoxide anion-driven inactivation and enhances its biological activity, suggesting that quercetin may scavenge superoxide anion in a Cu/Zn SOD, glutathione or ascorbic Acid-inhibitable manner.
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protective effect of quercetin a polyphenolic compound on mouse corpus cavernosum
Fundamental & Clinical Pharmacology, 2009Co-Authors: Peyman Ertug, Anil A Olguner, Nuran Ogulener, Ergin ŞingirikAbstract:Flavonoids are plant-based phenolic compounds, and quercetin is the most abundant dietary member of this family. One of the most important characteristics of quercetin is its antioxidant property. The aim of this study was to investigate antioxidant effects of quercetin on corpora cavernosa of mice. Corpora cavernosa were isolated in organ baths, precontracted with phenylephrine (0.5 microm) and relaxant responses were mediated by acetylcholine (0.1-1 microm), electrical field stimulation (EFS, 1-16 Hz, 0.5 ms, 30 V) or Acidified sodium nitrite (a NaNO(2), 0.5 mm). Superoxide anion generators; pyrogallol (50 microm), hydroquinone (100 microm), LY 83583 (6-Anilinoquinolin-5,8-quinone, 10 microm) and superoxide dismutase (SOD) inhibitor; Diethyldithiocarbamic Acid (DETCA, 8 mm) were used in order to expose corpus cavernosa to oxidant stress. Acetylcholine (0.1-1 microm) induced relaxant responses were significantly inhibited in LY 83583 (10 microm) and DETCA + LY 83583 applicated trials. EFS-induced relaxant responses were significantly inhibited in DETCA (8 mm) and DETCA + LY 83583 administrated trials. On the other hand, Acidified sodium nitrite-induced responses were inhibited by all of the superoxide anion generators tested. Quercetin (10 microm) failed to improve the inhibitions on endothelium and electrically stimulated responses. Acidified sodium nitrite (0.5 mm) mediated relaxant responses were significantly restored by quercetin except the groups in which LY 83583 were used. The data suggest that quercetin acts as a protective agent in mouse corpus cavernosum, increasing the bioavailability of exogenous nitric oxide by protecting it from superoxide anion (O(2)(-)).
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protective effect of quercetin a polyphenolic compound on mouse corpus cavernosum
Fundamental & Clinical Pharmacology, 2009Co-Authors: Peyman Ertug, Anil A Olguner, Nuran Ogulener, Ergin ŞingirikAbstract:Flavonoids are plant-based phenolic compounds, and quercetin is the most abundant dietary member of this family. One of the most important characteristics of quercetin is its antioxidant property. The aim of this study was to investigate antioxidant effects of quercetin on corpora cavernosa of mice. Corpora cavernosa were isolated in organ baths, precontracted with phenylephrine (0.5 microm) and relaxant responses were mediated by acetylcholine (0.1-1 microm), electrical field stimulation (EFS, 1-16 Hz, 0.5 ms, 30 V) or Acidified sodium nitrite (a NaNO(2), 0.5 mm). Superoxide anion generators; pyrogallol (50 microm), hydroquinone (100 microm), LY 83583 (6-Anilinoquinolin-5,8-quinone, 10 microm) and superoxide dismutase (SOD) inhibitor; Diethyldithiocarbamic Acid (DETCA, 8 mm) were used in order to expose corpus cavernosa to oxidant stress. Acetylcholine (0.1-1 microm) induced relaxant responses were significantly inhibited in LY 83583 (10 microm) and DETCA + LY 83583 applicated trials. EFS-induced relaxant responses were significantly inhibited in DETCA (8 mm) and DETCA + LY 83583 administrated trials. On the other hand, Acidified sodium nitrite-induced responses were inhibited by all of the superoxide anion generators tested. Quercetin (10 microm) failed to improve the inhibitions on endothelium and electrically stimulated responses. Acidified sodium nitrite (0.5 mm) mediated relaxant responses were significantly restored by quercetin except the groups in which LY 83583 were used. The data suggest that quercetin acts as a protective agent in mouse corpus cavernosum, increasing the bioavailability of exogenous nitric oxide by protecting it from superoxide anion (O(2)(-)).
Nuran Ogulener - One of the best experts on this subject based on the ideXlab platform.
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comparative study of the quercetin ascorbic Acid glutathione and superoxide dismutase for nitric oxide protecting effects in mouse gastric fundus
European Journal of Pharmacology, 2013Co-Authors: Peyman Ertug, Ergin Şingirik, Fatma Aydinoglu, Ozlem Goruroglu Ozturk, Nuran OgulenerAbstract:Abstract The aim of this work was to compare the preventing capacity of quercetin with Cu/Zn superoxide dismutase (Cu/Zn SOD), ascorbic Acid and glutathione on nitric oxide (NO)-induced relaxation in mouse gastric fundus. Furthermore, the effects of the quercetin on the tissue level of total oxidant and antioxidant was investigated. Nitrergic stimulation (4 Hz, 25 V, 0.1 ms, 10 s-train) and exogenous NO (10 μM) induced relaxation. Pyrogallol (10 μM), hydroquinone (100 μM) and LY83583 (6-Anilino-quinolin-5,8-quinone, 5 μM) inhibited nitrergic relaxations. The inhibition observed with pyrogallol, hydroquinone and LY83583 was prevented by quercetin (0.1 μM). Also, ascorbic Acid (500 μM), glutathione (100 μM) and Cu/Zn SOD (100 U/ml) prevented the inhibitory effect of superoxide anion generators on the relaxation to nitrergic stimulation and NO. Diethyldithiocarbamic Acid (DETCA; 8 mM) inhibited nitrergic relaxations. DETCA-induced inhibition on nitrergic stimulation and NO-induced relaxation was prevented by quercetin, ascorbic Acid, glutathione or Cu/Zn SOD. DETCA plus pyrogallol, hydroquinone or LY83583 strengthened the inhibition on the relaxations. Also, pre-treatment with quercetin, ascorbic Acid and glutathione prevented the inhibitory effect of DETCA plus LY-83583 on the relaxation to nitrergic stimulation and NO but Cu/Zn SOD did not prevent this inhibition. Also, quercetin increased tissue total antioxidant capacity and decreased tissue oxidant level and oxidative stress index in DETCA-treatment group. These results indicate that quercetin has antioxidant effect and protects NO from endogenous superoxide anion-driven inactivation and enhances its biological activity, suggesting that quercetin may scavenge superoxide anion in a Cu/Zn SOD, glutathione or ascorbic Acid-inhibitable manner.
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protective effect of quercetin a polyphenolic compound on mouse corpus cavernosum
Fundamental & Clinical Pharmacology, 2009Co-Authors: Peyman Ertug, Anil A Olguner, Nuran Ogulener, Ergin ŞingirikAbstract:Flavonoids are plant-based phenolic compounds, and quercetin is the most abundant dietary member of this family. One of the most important characteristics of quercetin is its antioxidant property. The aim of this study was to investigate antioxidant effects of quercetin on corpora cavernosa of mice. Corpora cavernosa were isolated in organ baths, precontracted with phenylephrine (0.5 microm) and relaxant responses were mediated by acetylcholine (0.1-1 microm), electrical field stimulation (EFS, 1-16 Hz, 0.5 ms, 30 V) or Acidified sodium nitrite (a NaNO(2), 0.5 mm). Superoxide anion generators; pyrogallol (50 microm), hydroquinone (100 microm), LY 83583 (6-Anilinoquinolin-5,8-quinone, 10 microm) and superoxide dismutase (SOD) inhibitor; Diethyldithiocarbamic Acid (DETCA, 8 mm) were used in order to expose corpus cavernosa to oxidant stress. Acetylcholine (0.1-1 microm) induced relaxant responses were significantly inhibited in LY 83583 (10 microm) and DETCA + LY 83583 applicated trials. EFS-induced relaxant responses were significantly inhibited in DETCA (8 mm) and DETCA + LY 83583 administrated trials. On the other hand, Acidified sodium nitrite-induced responses were inhibited by all of the superoxide anion generators tested. Quercetin (10 microm) failed to improve the inhibitions on endothelium and electrically stimulated responses. Acidified sodium nitrite (0.5 mm) mediated relaxant responses were significantly restored by quercetin except the groups in which LY 83583 were used. The data suggest that quercetin acts as a protective agent in mouse corpus cavernosum, increasing the bioavailability of exogenous nitric oxide by protecting it from superoxide anion (O(2)(-)).
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protective effect of quercetin a polyphenolic compound on mouse corpus cavernosum
Fundamental & Clinical Pharmacology, 2009Co-Authors: Peyman Ertug, Anil A Olguner, Nuran Ogulener, Ergin ŞingirikAbstract:Flavonoids are plant-based phenolic compounds, and quercetin is the most abundant dietary member of this family. One of the most important characteristics of quercetin is its antioxidant property. The aim of this study was to investigate antioxidant effects of quercetin on corpora cavernosa of mice. Corpora cavernosa were isolated in organ baths, precontracted with phenylephrine (0.5 microm) and relaxant responses were mediated by acetylcholine (0.1-1 microm), electrical field stimulation (EFS, 1-16 Hz, 0.5 ms, 30 V) or Acidified sodium nitrite (a NaNO(2), 0.5 mm). Superoxide anion generators; pyrogallol (50 microm), hydroquinone (100 microm), LY 83583 (6-Anilinoquinolin-5,8-quinone, 10 microm) and superoxide dismutase (SOD) inhibitor; Diethyldithiocarbamic Acid (DETCA, 8 mm) were used in order to expose corpus cavernosa to oxidant stress. Acetylcholine (0.1-1 microm) induced relaxant responses were significantly inhibited in LY 83583 (10 microm) and DETCA + LY 83583 applicated trials. EFS-induced relaxant responses were significantly inhibited in DETCA (8 mm) and DETCA + LY 83583 administrated trials. On the other hand, Acidified sodium nitrite-induced responses were inhibited by all of the superoxide anion generators tested. Quercetin (10 microm) failed to improve the inhibitions on endothelium and electrically stimulated responses. Acidified sodium nitrite (0.5 mm) mediated relaxant responses were significantly restored by quercetin except the groups in which LY 83583 were used. The data suggest that quercetin acts as a protective agent in mouse corpus cavernosum, increasing the bioavailability of exogenous nitric oxide by protecting it from superoxide anion (O(2)(-)).
Christopher J Gorski - One of the best experts on this subject based on the ideXlab platform.
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characterization of dextromethorphan n demethylation by human liver microsomes contribution of the cytochrome p450 3a cyp3a subfamily
Biochemical Pharmacology, 1994Co-Authors: Christopher J Gorski, Steven A Wrighton, Stephen D. Hall, David R JonesAbstract:In an effort to identify the human cytochromes P450 involved in the N-demethylation of dextromethorphan, the kinetics of 3-methoxymorphinan formation were studied in microsomal enzyme systems. Under initial rate conditions, 3-methoxymorphinan formation demonstrated single enzyme Michaelis-Menten kinetics using microsomes obtained from three human livers (Km: 0.52–0.71 mM; Vmax: 375–812 pmol/mg protein/min). B-lymphoblastoid cells expressing CYP3A4 incubated with 0.4 mM dextromethorphan catalyzed the formation of 3-methoxymorphinan at a rate of 22 pmol product/mg protein/min. Midazolam, a prototypic substrate for CYP3A4 and CYP3A5, competitively inhibited dextromethorphan N-demethylation by two human liver microsomal samples with Ki values of 46 ± 10 and 63 ± 8 μM. At a dextromethorphan concentration of 0.4 mM, gestodene (100 μM) inhibited 3-methoxymorphinan formation by approximately 50%. Immunoinhibition of dextro-methorphan N-demethylation using rabbit anti-CYP3A4 antibodies resulted in a 60% decrease in 3-methoxymorphinan formation at a dextromethorphan concentration of 0.4 mM. Additional inhibition studies using furafylline, coumarin, sulfaphenazole, mephenytoin, quinidine, and Diethyldithiocarbamic Acid, which are selective inhibitors of CYP1A2, CYP2A6, CYP2C8/9, CYP2Cmp, CYP2D6, and CYP2E1, respectively, demonstrated no substantial inhibition of dextromethorphan N-demethylation. Correlation analysis was performed using the rate of 3-methoxymorphinan formation at a concentration of 1mM dextromethorphan and immunoquantified levels of CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4, and CYP3A5 and their associated characteristic catalytic activities. A significant correlation was observed between dextromethorphan N-demethylase activity and midazolam 1'- and 4-hydroxylase activity (r2 = 0.77 and 0.69 respectively, N = 19, P < 0.01); the exclusion of those samples containing both CYP3A4 and CYP3A5 increased the correlation significantly (r2 = 0.87 and 0.91 respectively, N = 12, P < 0.01). In the absence of CYP3A5, a significant correlation was observed between 3-methoxymorphinan formation and the sample's erythromycin N-demethylase activity (r2= 0.94, N = 12, P < 0.01), testosterone 6 β-hydroxylase activity (r2 = 0.96, N = 7, P < 0.01) and relative immunoquantified levels of CYP3A4 (r2 = 0.96, N = 12, P < 0.01). Inclusion of those samples expressing CYP3A5 in addition to CYP3A4 reduced the magnitude of the observed correlation. No significant correlation between 3-methoxymorphinan formation and the sample's relative immunoquantified levels of or form-selective activity associated with CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19 (or CYP2Cmp), CYP2D6, and CYP2E1 was observed. In conclusion, dextromethorphan N-demethylation appears to be catalyzed primarily by CYP3A4 and to a lesser extent by CYP3A5 in vitro in humans. Thus, the administration of dextromethorphan to human volunteers may provide a means of simultaneously phenotyping the in vivo activity of CYP2D6 and CYP3A.
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characterization of dextromethorphan n demethylation by human liver microsomes contribution of the cytochrome p450 3a cyp3a subfamily
Biochemical Pharmacology, 1994Co-Authors: Christopher J Gorski, Steven A Wrighton, Stephen D. Hall, David R JonesAbstract:In an effort to identify the human cytochromes P450 involved in the N-demethylation of dextromethorphan, the kinetics of 3-methoxymorphinan formation were studied in microsomal enzyme systems. Under initial rate conditions, 3-methoxymorphinan formation demonstrated single enzyme Michaelis-Menten kinetics using microsomes obtained from three human livers (Km: 0.52-0.71 mM; Vmax: 375-812 pmol/mg protein/min). B-lymphoblastoid cells expressing CYP3A4 incubated with 0.4 mM dextromethorphan catalyzed the formation of 3-methoxymorphinan at a rate of 22 pmol product/mg protein/min. Midazolam, a prototypic substrate for CYP3A4 and CYP3A5, competitively inhibited dextromethorphan N-demethylation by two human liver microsomal samples with Ki values of 46 +/- 10 and 63 +/- 8 microM. At a dextromethorphan concentration of 0.4 mM, gestodene (100 microM) inhibited 3-methoxymorphinan formation by approximately 50%. Immunoinhibition of dextromethorphan N-demethylation using rabbit anti-CYP3A4 antibodies resulted in a 60% decrease in 3-methoxymorphinan formation at a dextromethorphan concentration of 0.4 mM. Additional inhibition studies using furafylline, coumarin, sulfaphenazole, mephenytoin, quinidine, and Diethyldithiocarbamic Acid, which are selective inhibitors of CYP1A2, CYP2A6, CYP2C8/9, CYP2Cmp, CYP2D6, and CYP2E1, respectively, demonstrated no substantial inhibition of dextromethorphan N-demethylation. Correlation analysis was performed using the rate of 3-methoxymorphinan formation at a concentration of 1 mM dextromethorphan and immunoquantified levels of CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4, and CYP3A5 and their associated characteristic catalytic activities. A significant correlation was observed between dextromethorphan N-demethylase activity and midazolam 1'- and 4-hydroxylase activity (r2 = 0.77 and 0.69 respectively, N = 19, P < 0.01); the exclusion of those samples containing both CYP3A4 and CYP3A5 increased the correlation significantly (r2 = 0.87 and 0.91 respectively, N = 12, P < 0.01). In the absence of CYP3A5, a significant correlation was observed between 3-methoxymorphinan formation and the sample's erythromycin N-demethylase activity (r2 = 0.94, N = 12, P < 0.01), testosterone 6 beta-hydroxylase activity (r2 = 0.96, N = 7, P < 0.01) and relative immunoquantified levels of CYP3A4 (r2 = 0.96, N = 12, P < 0.01). Inclusion of those samples expressing CYP3A5 in addition to CYP3A4 reduced the magnitude of the observed correlation. No significant correlation between 3-methoxymorphinan formation and the sample's relative immunoquantified levels of or form-selective activity associated with CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19 (or CYP2Cmp), CYP2D6, and CYP2E1 was observed. In conclusion, dextromethorphan N-demethylation appears to be catalyzed primarily by CYP3A4 and to a lesser extent by CYP3A5 in vitro in humans.(ABSTRACT TRUNCATED AT 400 WORDS)