Aminopyrine Activity Research Articles

The effects of T-2 toxin exposure on liver drug metabolizing enzymes in rabbit

High doses of T-2 toxin are known to decrease protein synthesis and mono-oxygenase activities in rat liver. The purpose of this study was to investigate whether exposure at a low dose could alter the normal metabolism of the xenobiotic by the liver. Three doses of T-2 toxin, dissolved in olive oil, were orally and daily administered to New Zealand white rabbits for five days. At 0.5mg/kg, three of the five animals died, whereas only a weak decrease in body weight gain and moderate signs of toxicity occurred in rabbits receiving 0.25mg/kg/day, and the body weight increased without signs of toxicity at 0.1mg/kg/day. At 0.25mg/kg/day, total liver microsomal P450 content, and the activities of aminopyrine and benzphetamine N-demethylases, pentoxyresorufin O-depentylase, glutathione S-transferases accepting 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene as substrates, were decreased. By contrast, ethylmorphine and erythromycin N-demethylases, ethoxyresorufin and methoxyresorufin O-dealkylases, aniline hydroxylase, and UDP-glucuronyltransferase accepting p-nitrophenol as substrate, were unaffected. The expression of P450 1A1, 1A2, 2A1, and 2B4, but not P450 2C3 and 3A6, were also decreased, whereas microsomal conjugated dienes, fluorescent substances, and malondialdehyde contents were increased. At 0.1mg/kg/day, neither significant effects on drug metabolizing enzymes nor microsomal oxidative damages were obtained. Taken together, these results suggest that a short exposure time to the mycotoxin would not be associated with significant changes in the normal metabolism of xenobiotics by the liver.

P2A29 - The effects of T-2 toxin exposure on liver drug metabolizing enzymes in rabbit

High doses of T-2 toxin are known to decrease protein synthesis and mono-oxygenase activities in rat liver. The purpose of this study was to investigate whether exposure at a low dose could alter the normal metabolism of the xenobiotic by the liver. Three doses of T-2 toxin, dissolved in olive oil, were orally and daily administered to New Zealand white rabbits for five days. At 0.5 mg/kg, three of the five animals died, whereas only a weak decrease in body weight gain and moderate signs of toxicity occurred in rabbits receiving 0.25 mg/kg/day, and the body weight increased without signs of toxicity at 0.1 mg/kg/day. At 0.25 mg/kg/day, total liver microsomal P450 content, and the activities of aminopyrine and benzphetamine N-demethylases, pentoxyresorufin O-depentylase, glutathione S-transferases accepting 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene as substrates, were decreased. By contrast, ethylmorphine and erythromycin N-demethylases, ethoxyresorufin and methoxyresorufin O-dealkylases, aniline hydroxylase, and UDP-glucuronyltransferase accepting p-nitrophenol as substrate, were unaffected. The expression of P450 1A1, 1A2, 2A1, and 2B4, but not P450 2C3 and 3A6, were also decreased, whereas microsomal conjugated dienes, fluorescent substances, and malondialdehyde contents were increased. At 0.1 mg/kg/day, neither significant effects on drug metabolizing enzymes nor microsomal oxidative damages were obtained. Taken together, these results suggest that a short exposure time to the mycotoxin would not be associated with significant changes in the normal metabolism of xenobiotics by the liver.

Role of 3,4-Dichlorophenyl Methyl Sulfone, a Metabolite ofo-Dichlorobenzene, in the Changes in Hepatic Microsomal Drug-Metabolizing Enzymes Caused byo-Dichlorobenzene Administration in Rats

2,3- and 3,4-Dichlorophenyl methyl sulfoxides and 2,3- and 3,4-dichlorophenyl methyl sulfones (2,3- and 3,4-DCPSO2Mes) were detected in the urine of rats administeredo-dichlorobenzene (o-DCB). After administration ofo-DCB to rats, swift decreases were observed in the concentrations ofo-DCB in blood, liver, and kidneys, whereas 3,4-DCPSO2Me appeared in blood, liver, kidneys, and adipose tissue. The concentrations of 3,4-DCPSO2Me in the blood and three tissues reached maxima at 24 hr. Both aminopyrineN-demethylase and aniline hydroxylase activities and cytochrome P450 content of hepatic microsomes decreased 24 hr after administration ofo-DCB. In contrast, 3,4-DCPSO2Me increased the activities of these enzymes and cytochrome P450 and b5contents in rat liver microsomes. In both antibiotic-pretreated and bile duct-cannulated rats dosed witho-DCB, the concentrations of 2,3- and 3,4-DCPSO2Mes in blood, liver, kidneys, and adipose tissue were dramatically reduced. These findings suggest that the process of formation of methylsulfonyl metabolites ofo-DCB involves biliary secretion of DCPSO2Mes and/or their precursors which will be subjected to metabolism by intestinal microflora. In antibiotic-pretreated rats, the inhibitory effects ofo-DCB administration on the activities of aminopyrine- and aniline-metabolizing enzymes and the contents of cytochromes P450 and b5in hepatic microsomes were greater than those observed in the intact rats. In bile duct-cannulated rats, the decrease in aminopyrineN-demethylase activity after administration ofo-DCB was greater than that observed in the intact rats. These findings suggest that the apparent inhibition of drug-metabolizing enzymes byo-DCB is the result of simultaneous contrary effects, namely, the inductive effect of 3,4-DCPSO2Me and the stronger inhibitory effect of an unknown factor(s) on drug-metabolizing enzymes.

Role of 2,3,5-Trichlorophenyl Methyl Sulfone, a Metabolite of 1,2,4-Trichlorobenzene, in the Induction of Hepatic Microsomal Drug-Metabolizing Enzymes by 1,2,4-Trichlorobenzene in Rats

2,3,5- and 2,4,5-trichiorophenyl methyl sulfides, 2,3,5- and 2,4,5-trichlorophenyl methyl sulfoxides, and 2,3,5- and 2,4,5-trichlorophenyl methyl sulfones (TCPSO 2Mes) were detected in the urine of rats dosed with 1,2,4-trichlorobenzene (TCB). After the administration of 1,2,4-TCB to rats, swift decreases in concentrations of 1,2,4-TCB in blood, liver, kidneys, and adipose tissue were observed. On the other hand, 2,3,5-TCPSO 2Me appeared in blood, liver, kidneys, and adipose tissue and remained detectable in the blood and the three tissues until 120 hr. The increases in the activities of aminopyrine N-demethylase and aniline hydroxylase and the contents of cytochromes P450 and b 5 in hepatic microsomes produced by 1,2,4-TCB occurred after increases in the hepatic concentration of 2,3,5-TCPSO 2Me. 2,3,5- and 2,4,5-TCPSO 2Me increased the above four parameters in rat liver microsomes. The inducing intensity of 2,3,5-TCPSO 2Me was much higher than that of 2,4,5-TCPSO 2Me. 2,3,5-TCPSO 2Me was considered to be a potent inducer and to play a principal role in the induction by l,2,4-TCB. When l,2,4-TCB was injected ip into bile duct-cannulated rats, little 2,3,5-TCPSO 2Me was detected in blood, liver, kidneys, and adipose tissue. In the antibiotic-pretreated rats dosed with 1,2,4-TCB, 2,3,5-TCPSO 2Me concentrations in the blood and the three tissues markedly decreased. These findings suggest that the formation of methylsulfonyl metabolites from 1,2,4-TCB depends largely upon the metabolism of some precursor(s) excreted in the bile by intestinal microflora. The increasing effects of 1,2,4-TCB administration on the activities of aminopyrine- and aniline-metabolizing enzymes and the contents of cytochromes P450 and b 5 in hepatic microsomes were not observed in the bile duct-cannulated rats. These findings provide evidence that the induction of drug-metabolizing enzymes by 1,2,4-TCB is not due to the action of 1,2,4-TCB itself but is due to its methylsulfonyl metabolite, 2,3,5-TCPSO 2Me.

Effects of D-limonene on hepatic microsomal monooxygenase activity and paracetamol-induced glutathione depletion in mouse.

1. D-Limonene, a monoterpenoid constituent of citrus fruit oil, blocks tumour induction by chemical carcinogens in laboratory animals, apparently by preventing bioactivation of procarcinogens and by enhancing conjugation of proximal carcinogenic metabolites. 2. Inhibitory effects of D-limonene were measured in vitro using cytochrome P450 isoform-specific substrates. D-Limonene inhibited p-nitrophenol hydroxylase (pNP) activity in vitro in liver microsomes from acetone-, phenobarbital (PB)- and beta-naphthoflavone (BNF)-treated mouse, and 7-ethoxyresorufin O-deethylase (EROD) activity in microsomes from PB- and BNF-treated mouse. p-Nitrophenol and ethoxyresorufin are substrates for cytochromes P2E1 and P1A1, respectively. No inhibition of benzphetamine (BNZP) or aminopyrine (AP) demethylases by D-limonene was observed. 3. EROD, BNZP and AP activities in liver microsomes were increased 18 h after i.p. administration of D-limonene to acetone-induced mouse, while pNP activity was unchanged. The immunodetectable protein level of cytochrome P2B1 in non-acetone treated mouse was increased 18 h after D-limonene, with no differences in P2E1 or P1A1. 4. Acute D-limonene did not protect against paracetamol (acetaminophen)-induced depletion of liver reduced glutathione (GSH). A prolonged paracetamol challenge (0.6% diet for 10 days) elevated liver cytosolic GSH-S-transferase activity (GST) two-fold and decreased liver GSH to 46% of control values. Dietary D-limonene (1.0% diet for 10 days) maintained liver GSH concentrations at 92% of control values in the paracetamol-challenged mouse without altering GST activity. D-Limonene also increased liver GSH concentration (23%) in mouse fed 1.0% D-limonene alone.

抗腫瘍性多糖体, シゾフィラン(SPG)の体内動態に関する研究(第2報)SPGのラット肝薬物代謝酵素系に及ぼす影響

The effect of a single or multiple administration of sizofiran (SPG), an anti-tumor polysaccharide, on a hepatic drug-metabolizing enzyme system was studied in rats. When SPG was given intravenously at a single dose of 0.5 or 10 mg/kg, no alteration was observed in activities of aminopyrine (AP) N-demethylase and aniline hydroxylase, and in cytochrome P-450 (P-450) content in the livers of rats 48 h after dosing. However, only AP demethylase activity decreased by 34% after the administration of 200 mg/kg. Similarly, no change in the hepatic enzyme activities and P-450 content was observed for up to 180 d after a single dose of 10 mg/kg. Subcutaneous treatment of animals with either 10 or 40 mg/kg dose for 3 and 6 months resulted in no alteration in the enzyme activities and P-450 content. These results may indicate that the therapeutically effective dose of SPG has no effect on a hepatic drug-metabolizing enzyme system in rats.

Factors influencing survival at one year in patients with nonbiliary hepatic parenchymal cirrhosis

Transplantation may be considered for patients with advanced cirrhosis, however, adequate criteria for evaluating survival in those patients are ill-defined. The aim of the present study was to select, among several clinical and functional variables those that could best predict survival at one year. The data collected from 91 consecutive patients with parenchymal cirrhosis hospitalized in our center from February 1984 to January 1986 were subjected to stepwise logistic regression analysis. Death occurring during the first year following entry into the study was considered as a failure. During that period, there were no censored patients. Of 19 variables that entered into the analysis, only two were significant (P less than 0.01): presence (1: moderate; 2: severe) or absence (0) of ascites (A) and breath test (BT: % aminopyrine activity of administered dose at 2 hr). The logistic equation was: 1n (P/1 - P): - 1.95 A + 1.64 BT - 0.393, where P represented the probability of survival at one year. For each patient, P was calculated according to his A and BT values. Using a 0.7 probability cut-point to separate success from failure, 93% (70/75) of successes, 81% (13/16) of failures, and 91% (83/91) of both successes and failures could be correctly predicted. Predictive equations like the present preliminary one can be used in the future to better assess the risk of mortality in patients with parenchymal cirrhosis in whom liver transplantation is considered.

Acute Effect of Amitriptyline, Phenobarbital or Cobaltous Chloride on δ-Aminolevulinic Acid Synthetase, Heme Oxygenase and Microsomal Heme Content and Drug Metabolism in Rat Liver

Cobaltous chloride (CoCI2) caused very marked decreases of cytochrome P-450, b5 and total heme contents and an increase of heme oxygenase activity. On the contrary, phenobarbital (PB) increased hepatic drug-metabolizing enzymes, but the total heme content remained unchanged. On the other hand, amitriptyline (AMT) caused a marked increase of δ-aminolevulinic acid (δ-ALA) synthetase activity at 12 and 24 hr. In addition, the contents of total heme and cytochrome b5 and the activities of aminopyrine (AM) N-demethylase and aniline (AN) hydroxylase at 24 hr were also increased by AMT, whereas cytochrome P-450 content did not change. This may be explained by the fact that AMT would increase hepatic heme synthesis through the prolonged induction of d-ALA synthetase, but it may not cause an increase in cytochrome P-450 heme because there are increases in the contents of cytochrome b5 and total heme.

Effect of Sizofilan, an Immunomodulator, on Hepatic Microsomal Mixed-Function Oxidase Activities in Rats

Mixed-function oxidase activities of hepatic microsomal preparations from rats were examined after intraperitoneal administration of sizofilan (SPG), an immunomodulator. Repeated doses of SPG (3 mg/kg/12 hr, 4 times) depressed the hepatic cytochrome P-450 content and the activities of aminopyrine N-demeth-ylase and aniline hydroxylase.

Acute effect of amitriptyline, phenobarbital or cobaltous chloride on delta-aminolevulinic acid synthetase, heme oxygenase and microsomal heme content and drug metabolism in rat liver.

Cobaltous chloride (CoCl2) caused very marked decreases of cytochrome P-450, b5 and total heme contents and an increase of heme oxygenase activity. On the contrary, phenobarbital (PB) increased hepatic drug-metabolizing enzymes, but the total heme content remained unchanged. On the other hand, amitriptyline (AMT) caused a marked increase of delta-aminolevulinic acid (delta-ALA) synthetase activity at 12 and 24 hr. In addition, the contents of total heme and cytochrome b5 and the activities of aminopyrine (AM) N-demethylase and aniline (AN) hydroxylase at 24 hr were also increased by AMT, whereas cytochrome P-450 content did not change. This may be explained by the fact that AMT would increase hepatic heme synthesis through the prolonged induction of delta-ALA synthetase, but it may not cause an increase in cytochrome P-450 heme because there are increases in the contents of cytochrome b5 and total heme.

Effect of sizofilan, an immunomodulator, on hepatic microsomal mixed-function oxidase activities in rats.

Mixed-function oxidase activities of hepatic microsomal preparations from rats were examined after intraperitoneal administration of sizofilan (SPG), an immunomodulator. Repeated doses of SPG (3 mg/kg/12 hr, 4 times) depressed the hepatic cytochrome P-450 content and the activities of aminopyrine N-demethylase and aniline hydroxylase.

Evidence that methylsulfonyl metabolites of m-dichlorobenzene are causative substances of induction of hepatic microsomal drug-metabolizing enzymes by the parent compound in rats

This study was undertaken to clarify the relationship between the formation of 2,4- and 3,5-dichlorophenyl methyl sulfones, metabolites of m-dichlorobenzene (DCB), and their inducing effect on hepatic microsomal drug-metabolizing enzymes in rats. When m-DCB was injected ip into bile duct-cannulated rats, little or no methyl sulfones were detected in blood, liver, kidneys, adipose tissue, or bile. In the antibiotic-pretreated rats dosed with m-DCB, metabolite concentrations in the blood and the three tissues markedly decreased. These findings suggest that the formation of methylsulfonyl metabolites from m-DCB depends largely upon the metabolism of some precursor(s) excreted in the bile by intestinal microflora. The increasing effects of m-DCB administration on the activities of aminopyrine and aniline metabolizing enzymes and the contents of cytochromes P-450 and b 5 in hepatic microsomes were scarcely observed in the bile duct-cannulated and antibiotic-pretreated rats, in which the drug-metabolizing enzymes were able to be induced by phenobarbital treatment. On the other hand, in rats administered 2,4- or 3,5-dichlorophenyl methyl sulfone hepatic distribution of each methyl sulfone was similar to that in intact rats, and the degree of increase of the above four parameters was nearly the same as that in the intact rats. These findings provide evidence that the induction of drug-metabolizing enzymes by m-DCB is not due to the action of m-DCB but is due to its methylsulfonyl metabolites.

Combined effect of nitrogen dioxide and cold stress on the activity of the hepatic cytochrome P-450 system in rats

The combined effects of nitrogen dioxide (NO 2) and cold stress were assessed on the cytochrome P-450 system by measuring microsomal protein content, cytochrome P-450 content, aminopyrine activity, and aniline hydroxyalse activity in the liver of male Wistar rats exposed to 4 ppm NO 2 and/or environment (4°C) for 24 h, 14 days,a nd 30 days. Exposure to cold alone changed the activity of the cytochrome P-450 system during the exposure up to 30 days,a nd exposure to NO 2 alone also infleunce it after 14 days and 30 days of exposure. Interaction were observed in the effect on the cytochemical P-450 system when rats exposed to NO 2 and cold simultaneously. There was a tendency that NO 2 suppressed the increased in activities of the cytochrome P-450 system caused by cold of 24-h and 30-day exposure.

Comparison of hepatic drug-metabolizing enzymes induced by 3-methylcholanthrene and phenobarbital between pre- and postnatal rats

Effects of 3-methylcholanthrene (3MC) and phenobarbital (PB) on the hepatic drug-metabolizing enzyme system in fetal liver of rats were investigated. Intraperitoneal administration of 3MC (25 mg/kg, 72 and 48 hr before death) to pregnant rats significantly increased hexobarbital (HB) and aminopyrine (AM)-metabolizing activities in fetuses on the 21st day of gestation to 148.0 and 150.6% of control fetuses, respectively. In contrast, HB and AM-metabolizing activities in 4-day-old neonates and mothers were decreased by administration of 3MC on the 21st day of gestation. Benzo[a]pyrene (BP)-metabolizing activity, NADPH-cytochrome c reductase activity, and cytochrome P-450 content in 3MC-treated fetuses were significantly increased to 2143.6, 137.6, and 323.8% of the control, respectively. Following 3MC administration, the maximum absorption of the cytochrome P-450-CO difference spectra in liver microsomes of fetuses was observed at 449–450 nm. The induction profile following 3MC administration in the fetal livers was different from that in the neonatal and the maternal livers. On the other hand, intraperitoneal administration of PB (60 mg/kg, 72, 48, and 24 hr before death) significantly increased HB, AM, and BP-metabolizing activities in fetal livers to 263.7, 231.0, and 151.2% of the respective controls. The profile induced by PB in the fetal livers was similar to that in maternal livers. These results suggest that HB and AM-metabolizing enzymes in fetal livers treated with 3MC or PB possess the capacity to be induced, and the responsiveness of the drug-metabolizing enzyme system to 3MC during the prenatal stage may differ from the postnatal stage.