Metabolism of tetramethrin isomers in rat: II. Identification and quantitation of metabolites

1. To examine the metabolic fate of (1RS, trans)- or (1RS, cis)-tetramethrin [3, 4, 5, 6-tetrahydrophthalimidomethyl (1RS, trans)- or (1RS, cis)-chrysanthemate], rat was administered a single oral dose of trans- or cis-[alcohol-14C]tetramethrin at dose levels of 2 or 250 mg/kg. 2. The radiocarbon was almost completely eliminated from rat within 7 days after administration in all groups. 14C-recoveries (expressed as percentages relative to the dosed 14C) in faeces and urine were 38-58 and 42-58% respectively in rat administrated trans-[alcohol-14C]tetramethrin, and in faeces and urine were 66-91 and 9-31% respectively in rat administered cis-[alcohol-14C]tetramethrin. 3. Fourteen metabolites found in excreta were purified by using several chromatographic techniques and identified by spectroanalyses (nmr and MS). Five sulphonate derivatives and three dicarboxylic acid derivatives were found. 4. The main metabolites were sulphonate derivatives in the faeces, and in the urine, alcohols, dicarboxylic acid and reduced metabolites derived from the 3,4,5,6-tetrahydrophthalimide moiety.     

Metabolism of oral contraceptive drugs. The formation and disappearance of metabolites of norethindrone and mestranol after intravenous and oral administration

Previous studies from this laboratory reported that 3H-labeled metabolites with half-lives of more than 24 hours may remain in the plasmaa of women receiving an intravenous injection of 3H norethindrone or 3H mestranol. To confirm the presence of these metabolites, blood samples were collected for five days after injection of 3H norethindrone or 3H mestranol; 3H representing metabolites of norethindrone disappeared with half-life values of 42 to 84 hours (mean 67 hours), while 3H representing metabolites of mestranol declined with an average half-life of 45 hours (range 37 to 65 hours). When the 3H-labeled drugs were administered orally, metabolites of similar half-life were formed. Because these compounds exist for several days after a single administration and since oral contraceptive drugs are normally taken daily, the possiblity of the accumulation of 3H in the plasm of women receiving several consecutive doses of 3H norethindrone was investigated. The results of this study show a stepwise accumulation of the 3H metabolites when 3H norethindrone was administered in six daily oral doses. However, the 3H levels declined from the peak on the sixth and last day of the treatment at a rate equivalent to those previously measured after intravenous or oral administration.     

Metabolism of polycyclic aromatic hydrocarbons and covalent binding of metabolites to protein in rat adrenal gland

The metabolism of the carcinogenic and adrenocorticolytic polycyclic aromatic hydrocarbon 7,12-dimethylbenz(a)anthracene in rat adrenals was investigated. Both 7,12-dimethylbenz(a)anthracene and benzo(a)pyrene, which also is a well-known carcinogen but has no short-term effects on rat adrenals, appear to be metabolized by one common type of cytochrome P-450-dependent monooxygenase localized in the endoplasmic reticulum. Studies of the kinetic properties of this cytochrome P-450 reveal that the Km values for 7,12-dimethylbenz(a)anthracene and benzo(a)pyrene are lower than 3 microM. Identification of metabolites indicates that, with both 7,12-dimethylbenz(a)anthracene and benzo(a)pyrene, phenols and diols were formed the relative rates of formation of which were markedly influenced by the expoxide hydrase inhibitor cyclohexane oxide, suggesting that epoxides are intermediate metabolites. Added or endogenous microsomal glutathione S-transferase B had little or no effect on the distribution of metabolites. A rather selective binding of metabolites of 7,12-dimethylbenz(a)anthracene to soluble and microsomal proteins was demonstrated. The adrenal cytochrome P-450 involved in the conversion of these polycyclic aromatic hydrocarbons appears to be unrelated to those responsible for the synthesis of mineralocorticoids and glucocorticoids from cholesterol. Among androgens and estrogens, estradiol proved to be the most inhibitory steroid, suggesting a role of the hydrocarbon-metabolizing cytochrome P-450 in estrogen biosynthesis. However, no such function could be demonstrated conclusively. The metabolite patterns and the effects of nonsteroid inhibitors of liver monooxygenases, e.g., alpha-naphthoflavone, SU 9055, and ellipticine, suggest that the properties of this cytochrome P-450 resemble those of the 3-methyl-cholanthrene-inducible cytochrome P-488 from rat liver.     

Identification of an endonuclease responsible for apoptosis in rat thymocytes

We studied total occlusion of all three coronary arteries. From 1975 to 1992, a total of 4,100 patients underwent coronary arteriography at Show University Hospital. Of these, four patients (0.1%) had complete occlusion of all three coronary arteries and all of them underwent coronary artery bypass grafting (CABG). The mean numbers of coronary risk factors were only 2.3 but history of angina of effort were long-standing such as 4 to 29 years (mean 16.3 yr). All cases had previous episodes of myocardial infarction. Three cases (75%) had aortic aneurysm. One case was also diagnosed as Leriche syndrome besides coexisting aneurysm. Coronary arteriogram showed total occlusion of right coronary artery, left anterior descending artery and left circumflex artery in the segment of 1.6 or 7 and 11 respectively. All cases had intracoronary anastomosis and intercoronary anastomosis. Among 12 occluded coronary arteries of all four cases, 11 were distally visualized with contrast medium via collateral flow but good opacification of the distal coronary trees were not seen. Also proper assessments of cardiac performance including viability of myocardium were not established because all cases were in the state of C.C.S grades IV. But significant clinical recovery were obtained in all cases after CAGB of three or four bypass. We conclude that these results might be a useful suggestion for the treatment of total occlusion of all three coronary arteries.     

Pharmacokinetics of mivacurium isomers and their metabolites in healthy volunteers after intravenous bolus administration

BACKGROUND: Previous studies report the pharmacokinetics of mivacurium isomers after an infusion using venous blood sampling. Although the extent of the mivacurium arterial-venous gradient is not known, the sampling site is likely to influence mivacurium pharmacokinetic parameters because the drug is rapidly metabolized as it traverses the circulation. The objectives of this study were (1) to determine the pharmacokinetics of mivacurium isomers in healthy persons after intravenous bolus administration using intensive arterial blood sampling, and (2) to characterize the formation and elimination of mivacurium metabolites in human plasma. METHODS: Eight persons classified as American Society of Anesthesiologists physical status 1 or 2 who were scheduled to undergo elective surgery under balanced anesthesia received 0.15 mg/kg mivacurium chloride as an intravenous bolus. Arterial blood samples were collected every 10 s during the first 2 min and at frequent intervals for 4 h thereafter. Plasma concentrations of mivacurium isomers and their metabolites were determined by two stereoselective high-performance liquid chromatographic methods coupled with fluorometric detection and noncompartmental pharmacokinetic parameters. RESULTS: Mean elimination half-lives of the trans-trans, cis-trans, and cis-cis isomers were 2.4, 2, and 28.5 min, respectively, with corresponding mean plasma clearances of 29.2, 45.7, and 6.7 ml.min 1.kg-1. The volumes of distribution at steady state of the trans-trans, cis-trans, and cis-cis isomers were 0.047, 0.054, and 0.189 l/kg, respectively. Plasma concentrations of monoester and alcohol metabolites peaked 25 s (median) after mivacurium injection, with half-lives in the range of 90 min, except for the cis alcohol metabolite, which was only negligibly and transiently formed. CONCLUSIONS: Substantial hydrolysis of mivacurium isomers by cholinesterases was confirmed by the rapid appearance of mivacurium metabolites in plasma. The intensive arterial sampling proved to be critical for the trans-trans and cis-trans isomers because the area under the curve between 0 and 2 min accounted for 75% and 86% of the total, respectively.     

Metabolism of isbufylline in humans. Isolation, identification, and synthesis of plasma and urine metabolites

Isbufylline metabolism after oral administration to humans was studied. The main metabolites detected by the HPLC method, in plasma, were 1-methyl-7-(2-hydroxy-2-methyl-propyl) xanthine (I), 1,3-dimethyl-7-(2-hydroxy-2-methyl-propyl) xanthine (II), and 1-methyl-7-(2-methyl-propyl) xanthine (III). The main metabolites detected in urine were 1-methyl-7-(2-hydroxy-2-methyl-propyl) xanthine (I), 1,3-dimethyl-7-(2-carboxy-propyl) xanthine (IV), and 1,3-dimethyl-7-(2-hydroxymethyl-propyl) xanthine glucuronic acid (V)-Gluc. They were isolated by HPLC, identified by GC/MS, HPLC/MS, or HPLC/MS/MS, and finally synthesized. Recovery of these metabolites, along with the absence of unmetabolized isbufylline in the urine, indicated biotransformation and renal excretion as the main routes of isbufylline elimination in humans. HPLC quantitation of the characterized urine metabolites revealed that 49% of the drug was eliminated as (I), 9% as (V)-Gluc, and 5% as (IV).     

Depression and attributions: Factors responsible for inconsistent results in the published literature.

According to the attributional reformulation of learned helplessness, depressive symptoms are associated with an attributional style that points to internal and global causes for bad events involving the self. 61 tests of the attributional reformulation published in 6 journals (e.g., Cognitive Therapy and Research) since 1978 were analyzed to determine factors that might distinguish findings that corroborated the reformulation's predictions from those that did not. Use of a large sample and hypothetical events was correlated with support for the reformulation with respect to stable and global attributions. However, these characteristics were highly intercorrelated across studies, making it impossible to isolate their independent effects. None of the factors (e.g., nature of the sample, method of assessing depression) examined consistently distinguished supporting from nonsupporting studies with respect to internal attributions. (9 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multispecific organic anion transporter is responsible for the biliary excretion of the camptothecin derivative irinotecan and its metabolites in rats

Irinotecan, 7-ethyl-10-[4-(1-piperidino)-1-piperidino]-carbonyloxycamptothecin (CPT-11), is a potent anticancer drug that is increasingly used in chemotherapy. A frequent limiting side effect involves gastrointestinal toxicity (diarrhea), which is thought to be related to the biliary excretion of CPT-11 and its metabolites. Accordingly, the biliary excretion mechanisms for both the lactone and carboxylate forms of CPT-11 and its metabolites, SN-38 and its glucuronide (SN38-Glu), were investigated using Sprague-Dawley (SD) rats and Eisai hyperbilirubinemic rats (EHBR), with the latter being mutant rats with a genetic deficiency of the canalicular multispecific organic anion transporter. After i.v. administration of CPT-11, the biliary excretion clearance, defined as the biliary excretion rate normalized to the hepatic concentration, of both the lactone and carboxylate forms of SN38-Glu was much lower in EHBR. The biliary excretion clearance for the carboxylate form of both CPT-11 and SN-38 was also substantially smaller in EHBR and showed marked saturation with increasing dose only in SD rats. On the other hand, the biliary excretion clearance for the lactone forms of CPT-11 and SN-38 showed only a minimal difference in EHBR, compared with SD rats. These results suggest that, for the carboxylate form of CPT-11 and SN-38 and the carboxylate and lactone forms of SN38-Glu, there exists a specific transport system at the bile canalicular membrane that is deficient in EHBR. To confirm this hypothesis, the uptake of these substrates by isolated hepatic canalicular membrane vesicles (CMV) was examined. ATP-dependence was clearly observed for the uptake of these four compounds by CMV prepared from SD rats but not by CMV from EHBR. In addition, the compounds inhibited the ATP-dependent uptake of S-(2,4-dinitrophenyl) glutathione by CMV from SD rats, in a concentration-dependent manner. These results suggest that the biliary excretion of the carboxylate forms of CPT-11 and SN-38 and the carboxylate and lactone forms of SN38-Glu is mediated by the multispecific organic anion transporter, which is deficient in EHBR.     

Biotransformation of trithiozine. III - Isolation and identification of further metabolites in rat urine

The metabolism of a new antisecretory and antiulcer drug, trithiozine (I.S.F. 2001, T), was studied in 4 hr rat urine samples after i.p. administration. After extraction at pH 7 with chloroform, the urine was either incubated with beta-glucuronidase or acidified to pH 2 and subsequently extracted with chloroform. The organic layers were evaporated to dryness and the residues used for TLC analysis. The neutral extracts revealed five spots, not present in control rat urine, corresponding to the unchanged drug T and to four metabolites. Two of the metabolites had been previously identified as the 4-(3,4,5-trimethoxybenzoyl)tetrahydro-1,4-oxazine (TBO) and the 4-(3,4,5-trimethoxythiobenzoyl)tetrahydro-1,4-oxazine-S-oxide (TO). Three other metabolites were found in the extracts after beta-glucuronidase incubation. TLC, U.V. and M.S. data were consistent with the structure 4-(3,5-dimethoxy-4-hydroxythiobenzoyl)tetrahydro-1,4-oxazine (HT), the corresponding S-oxide (HO) and the 4-(3,5-dimethoxy-4-hydroxybenzoyl)tetrahydro-1,4-oxazine (HBO). The acidic extracts revealed two spots structurally identified as the 3,4,5-trimethoxybenzoic acid (TBA) and the previous HBO. On the basis of present knowledge, a possible metabolic pathway of T is reported, consisting in a rapid metabolic oxidation on the sulfur atom and a slower demethylation on the para methoxy group. The presence of TBA is indicative of subsequent enzymatic hydrolysis of TBO. The intense and long-lasting inhibitory effect of T on gastric secretion is tentatively correlated with the pharmacological activities of some of its metabolites.     

Studies on rat hair cultures. IV. The effects of testosterone and dihydrotestosterone

An attempt was made to ameliorate or eliminate the teratogenicity of experimental amniocentesis a) by reducing the calibre of the needle used to puncture the amniotic membranes, and b) by applying a surgical hemostatic sponge over the puncture site. It was found that although neither attempts altered the deleterious effects of amniocentesis on the fetal parameters of weight, crownrump length, and length-weight ratio, the incidence of fetal mortality decreased as the calibre of the needle was reduced. Evidence regarding the ability of the Gelfoam seal to ameliorate the teratogenicity of amniocentesis was conflicting and inconclusive.     

Urinary metabolites of p-hydroxyamphetamine in man, rat and guinea-pig

1. The metabolism of (+/-)-p-hydroxy[14C]amphetamine has been studied in the rat, guinea-pig and man. 2. Most of the administered 14C was excreted in the urine within the first 24 h (64-92%), and was present mainly as free and conjugated p-hydroxy[14C]-amphetamine. In the female rat and female guinea-pig the conjugate was a glucuronide, but in man, who received a much smaller dose, the conjugate was a sulphate ester. A sex difference in conjugation was found in the rat, the female partly conjugating the drug but not the male. 3. Small quantities (1-6% of dose) of p-hydroxynorephedrine, a putative false neurotransmitter, were found in the urine of the three species. 4. Some oxidative degradation of the side chain of p-hydroxyamphetamine occurred in rat and guinea-pig since small amounts of p-hydroxybenzoic acid (1-3%) were detected in the urine.     

Metabolism of debrisoquine sulphate in rat, dog and man

1. The metabolism of debrisoquine sulphate in the dog has been studied and is similar to that in rat and man. 2. Two acidic urinary metabolites, shown to be present in rat, dog and man, have been isolated from rat urine. After derivatization they were characterized by n.m.r. and mass spectroscopy as methyl 2-[2-(4,6-dimethylpyrimidylamino)-methyl]-phenylacetate and 2-[2-(4,6-dimethylpyrimidylamino)-ethyl]benzoate.     

Metabolism of oxytocin in rat uterus and placenta in late gestation

Concentrations of oxytocin (OT) peptide increase in rat uterine tissues at the time of parturition. We have measured the rate of OT metabolism in these tissues in late gestation to determine whether a decrease in OT catabolism is responsible for the increase in OT concentrations. Uterine and placental tissues were obtained from groups of rats at Days 16, 19, 21, 21.5, 22, and after delivery of the first pup. Delivery usually occurs in the early afternoon of Day 22. Some animals were treated with the estrogen receptor blocker tamoxifen, which will delay parturition by approximately 24 h. Cytosolic and microsomal preparations obtained using ultracentrifugation were incubated with radiolabeled OT. Metabolites were separated using HPLC, and enzyme kinetic parameters were calculated. OT was actively metabolized in both uterine and placental tissues. Total oxytocinase activity was similar in the two tissues. In uterine tissues, activity was greater in the cytosolic fractions. In placenta, activity was evenly distributed between the cytosolic and microsomal fractions. The cytosolic fractions of each tissue contained predominantly post-proline endopeptidase activity, whereas the microsomes contained predominantly aminopeptidase activity. There was a slight trend to decreasing oxytocinase activity with advancing gestation in both subcellular fractions, but this was statistically significant only in the microsomal fraction. The maximal decline in activity was only 25-50%. Tamoxifen treatment had no effect on oxytocinase activity. We conclude that rat uterine and placental tissues contain post-proline endopeptidase and aminopeptidase activities that metabolize OT. It is doubtful that changes in these activities are major factors in regulating the increase in OT concentrations measured in rat intrauterine tissues at the time of parturition.