Pentoxyresorufin

Skf 525-A induces cocaine N-demethylase, ethoxyresorufin O-deethylase, and pentoxyresorufin O-dealkylase activities by induction of cytochrome p-450 2B in female B6C3F1 mice.[Pubmed:15513895]

J Toxicol Environ Health A. 2004 Dec;67(23-24):1955-70.

Studies demonstrated that cocaine-induced immunosuppression is mediated by metabolites of cocaine. Although SKF 525-A inhibited cocaine N-demethylation in liver S9 fractions isolated from female B6C3F1 mice, our study showed that pretreatment of mice with SKF 525-A potentiated cocaine-induced suppression of the antibody response to sheep red blood cells. An increase in formaldehyde generation was subsequently shown following incubation of cocaine with the S9 fractions prepared from SKF 525-A-treated mice, indicating the possibility of cytochrome P-450 (CYP) induction. Therefore, the inductive effects of SKF 525-A on CYP enzyme activities and proteins were investigated in female B6C3F1 mice to elucidate the potentiation of cocaine-induced immunosuppression by SKF 525-A. When SKF 525-A was administered at 10, 20, or 40 mg/kg/d intraperitoneally for 7 consecutive days, both ethoxyresorufin O-deethylase and Pentoxyresorufin O-dealkylase activities were induced dose-dependently. Furthermore, the induction of enzymatic activity was time dependent. Meanwhile, when the type of isozyme induced by SKF 525-A was analyzed by Western immunoblotting with monospecific anti-CYP 1A and anti-CYP 2B antibodies, only the CYP 2B appeared to be induced. From in vitro inhibition studies with monoclonal antibodies, it was confirmed that the induced activity of ethoxyresorufin O-deethylase by SKF 525-A was due to increased levels of CYP 2B proteins. Our present results provide an explanation for the potentiation of cocaine-induced immunosuppression by repeated exposure to SKF 525-A. Our results also indicate that ethoxyresorufin O-deethylase, a selective substrate for CYP 1A, may also be catalyzed by CYP 2B.

Liquid|liquid|electrode triple-phase boundary photovoltammetry of pentoxyresorufin in 4-(3-phenylpropyl)pyridine.[Pubmed:21488643]

Langmuir. 2011 May 17;27(10):6471-7.

Voltammetric responses of Pentoxyresorufin in 4-(3-phenylpropyl)-pyridine (PPP) microdroplets immersed in aqueous electrolyte are investigated in the absence and in the presence of light. The reduction of Pentoxyresorufin to leuco-Pentoxyresorufin in the dark is shown to occur in a two-electron, two-proton process sensitive to the aqueous pH and the PPP|aqueous electrolyte interfacial tension. No significant net photoelectrochemical current responses are observed, although transient responses indicative of distinct electron and hole charge carriers are seen in the presence of Pentoxyresorufin. EPR evidence confirms the formation of radical intermediates upon illumination. As a coreactant, duroquinone in the PPP microdroplet phase is investigated and also shown to undergo two-electron, two-proton reduction (to duroquinol) without significant photoelectrochemical activity. When investigated in combination, Pentoxyresorufin acts as a photocatalyst for the oxidation of duroquinol to duroquinone. Wavelength-resolved photovoltammetry experiments clearly implicate Pentoxyresorufin as the primary photoexcited intermediate. The photoelectrochemical mechanism is explained on the basis of the presence of a long-lived (possibly charge-separated) photoexcited intermediate in the PPP microphase. Implications for light-energy harvesting are discussed.

Ginkgo biloba extract markedly induces pentoxyresorufin O-dealkylase activity in rats.[Pubmed:12501011]

Jpn J Pharmacol. 2002 Dec;90(4):345-51.

We examined the effect of Ginkgo biloba extract (GBE) on hepatic drug-metabolizing enzymes, particularly cytochrome P450 (CYP), in rats. Rats were fed a GBE-containing diet or received GBE by intragastric gavage. The concentration of CYP and activity of various CYP enzymes in the liver were increased in a dose- and time-dependent manner. Significant increases in the concentration and activities of CYP enzymes were detected on day 1 of feeding of a 0.5% GBE diet and after administration of 10 mg GBE/kg body weight for 5 days by intragastric gavage. Among the CYP enzymes, the activity of Pentoxyresorufin O-dealkylase (PROD), a CYP2B enzyme, was especially markedly increased. The induction of CYP2B enzyme by GBE was confirmed by Western blot analysis. Addition of GBE to a CYP assay system in vitro caused concentration-dependent inhibition of various CYP enzyme activities. The inhibition was more marked for the microsomal enzymes from GBE-treated rats than for those from control rats and more marked against PROD activity among the CYP enzymes tested. When the inhibition of various CYP enzymes activities by GBE in vitro was compared, no marked difference was observed between rat and human hepatic microsomal enzymes. These results indicate that excess intake of GBE induces CYP enzymes, particularly PROD, and may modify the efficacy of drugs taken simultaneously.

Hepatic ethoxy-, methoxy- and pentoxyresorufin O-dealkylase activities in Landrace and Duroc pigs stimulated with HCG.[Pubmed:19930133]

Reprod Domest Anim. 2010 Dec;45(6):e269-74.

The effect of human chorionic gonadotropin (hCG) stimulation on the activities of ethoxyresorufin O-deethylase (EROD), methoxyresorufin O-demethylase (MROD) and Pentoxyresorufin O-depentylase (PROD) was studied in intact male pigs of purebred Landrace and Duroc breeds. Pigs were divided into four groups: two control groups of each breed, without hCG stimulation (n = 20 for each breed), and two experimental groups (n = 18 for each breed), with hCG stimulation (Pregnyl((R)); N.V. Organon, Oss, The Netherlands, 30 IU/kg live weight). Pigs were slaughtered 3 days after hCG stimulation and enzyme activities were measured in hepatic microsomes using two approaches. First, only one substrate concentration was used for the analysis of each enzyme activity. We found that EROD activity was suppressed by hCG-stimulation in Landrace (p = 0.004), but not Duroc pigs (p > 0.05). Generally, EROD activity was higher in Duroc pigs compared with Landrace (p = 0.017). Methoxyresorufin O-demethylase and PROD activities did not differ between groups (p > 0.05). To further characterize EROD, MROD and PROD, enzyme kinetic studies were performed. V(max) values for EROD and MROD in both breeds were lower after hCG stimulation (p < 0.001 for Landrace and p < 0.05 for Duroc). Additionally, V(max) values for EROD significantly differed between Landrace and Duroc pigs being higher in Duroc pigs (p < 0.05). We concluded that both hCG stimulation and breed differences may be important in the regulation of EROD and MROD activities. This study provides the first data on the effect of hCG stimulation and thus high testicular steroids, on EROD, MROD and PROD activities. Further studies are needed to investigate individual CYP450 enzymes and their regulation in porcine tissues.

Dealkylation of pentoxyresorufin: a rapid and sensitive assay for measuring induction of cytochrome(s) P-450 by phenobarbital and other xenobiotics in the rat.[Pubmed:3985627]

Arch Biochem Biophys. 1985 Apr;238(1):43-8.

The O-dealkylation of Pentoxyresorufin (7-pentoxyphenoxazone) by rat liver microsomes was examined. The reaction appeared highly specific for certain phenobarbital inducible forms of cytochrome P-450 and was increased 95- to 140-fold by animal pretreatment with phenobarbital (75 mg/kg/day, four ip injections) and approximately 50-fold by Aroclor 1254 (500 mg/kg, one ip injection) while animal pretreatment with 3-methylcholanthrene (50 mg/kg/day, three ip injections) resulted in less than a 2-fold increase over the rate detected in control microsomes. It was observed that this activity, in microsomes for Aroclor-pretreated rats, was dependent on O2 and was inhibited by metyrapone and SKF 525-A, indicative of cytochrome(s) P-450 mediation in the reaction. When antibodies directed against purified cytochrome(s) P-450s were employed to inhibit the Pentoxyresorufin O-dealkylation reaction, antibodies to P-450PB-B greatly inhibited the reaction (greater than 90%), while antibodies to P-450PB-C or P-450PB/PCN-E had minimal effects. Assay of hepatic microsomes from rats which were pretreated with varying doses of phenobarbital (0.9-75 mg/kg/day, four ip injections) indicated that while aminopyrine-N-demethylase activity was induced only 2-fold at the maximum dose (75 mg/kg/day), Pentoxyresorufin O-dealkylase activity was induced approximately 140-fold at this dose and approximately 4-fold by a dose of phenobarbital as low as 0.9 mg/kg.