Search

Deciphering the metabolites of multiple components in herbal medicine has far-reaching significance for revealing pharmacodynamic ingredients. However, most chemical components of herbal medicine are secondary metabolites with low content whose in vivo metabolites are close to trace amounts, making it difficult to achieve comprehensive detection and identification. In this paper, an efficient strategy was proposed: herb-derived metabolites were predicted according to the structural characteristics and metabolic reactions of chemical constituents in Corydalis Rhizoma and chemical structure screening tables for metabolites were conducted. The fragmentation patterns were summarized from representative standards combining with specific cleavage behaviors to deduce structures of metabolites. Ion abundance plays an important role in compound identification, and high ion abundance can improve identification accuracy. The types of metabolites in different biological samples were very similar, but their ion abundance might be different. Therefore, for trace metabolites in biological samples, we used the following two methods to process: metabolites of high dose herbal extract were analyzed to characterize those of clinical dose herbal extracts in the same biological samples; cross-mapping of different biological samples was applied to identify trace metabolites based on the fact that a metabolite has different ion abundance in different biological samples. Compared with not using this strategy, 44 more metabolites of clinical dose herbal extract were detected. This study improved the depth, breadth, and accuracy of current methods for herb-derived metabolites characterization., Graphical abstract Image 1, Highlights • Cross-mapping of different doses and samples was used to detect trace herb-derived metabolites. • Herb-derived metabolites were predicted by chemical structure screening tables, which were conducted according to structural characteristics and metabolic reactions. • The metabolic characteristic fragments (MCFs) were proposed to filter structure types of metabolites. • The relationship between structure and metabolism of Yanhusuo alkaloids was demonstrated.

Γ-Valero-lactone (GVL) is a freely marketed organic solvent and food additive. GVL is also an underrated legal substitute for γ-hydroxybutyric acid (GHB), and it is sold under the trade name "Tranquili-G". GVL is usually not included in forensic drug testing, even though it has been reported in drug-facilitated sexual assaults (DFSA). To date, few studies verified the effectiveness of GVL as a hypnotic/narcotic substance, and no data are available on its urinary excretion profile. This work aims to fill this knowledge gap and lead to the introduction of GVL in forensic drug testing, especially when DFSA is suspected. To monitor the timeframe of GVL activity in vivo, we have assessed the effects on sensorimotor responses in visual placing tests carried out on CD-1 mice at a dose of 400 mg/kg of GVL, administered by gastric gavage. In parallel, samples of the in vitro and in vivo metabolism studies were analyzed using a rapid and cost-effective analytical procedure based on gas chromatography coupled to mass spectrometry. Our data confirmed that GVL impairs visual placing response in mice in the first 4 hours after the intake, and they also show that GVL is a less potent substitute of GHB. The urinary excretion profile of GVL is consistent with the results of the behavioral study, with a maximum of excretion in the first 5 hours after the intake. GVL is only detectable in the first 0-8 hours after the intake. Our data confirmed the same rapid urinary excretion rate of GHB in urine and the related forensic implications, with the risk of possible false-negative results, especially when DFSA is suspected.

Introduction The aim of this work was to study the biodistribution, metabolism and radiation dosimetry of rats injected with [18F]FNM using PET/CT images. This novel radiotracer targeting NMDA receptor has potential for investigation for neurological and psychiatric diseases. Methods Free fraction and stability in fresh human plasma were determined in vitro. PET/CT was performed on anesthetized rats. Organs were identified and 3D volumes of interest (VOIs) were manually drawn on the CT in the center of each organ. Time activity curves (TACs) were created with these VOIs, enabling the calculation of residence times. To confirm these values, ex vivo measurements of organs were performed. Plasma and urine were also collected to study in vivo metabolism. Data was extrapolated to humans, effective doses were estimated using ICRP-60 and ICRP-89 dosimetric models and absorbed doses were estimated using OLINDA/EXM V1.0 and OLINDA/EXM V2.0 (which use weighting factors from ICRP-103 to do the calculations). Results The [18F]FNM was stable in human plasma and the diffusible free fraction was 53%. As with memantine, this tracer is poorly metabolized in vivo. Ex vivo distributions validated PET/CT data as well as demonstrating a decrease of radiotracer uptake in the brain due to anesthesia. Total effective dose was around 6.11 μSv/MBq and 4.65 μSv/MBq for female and male human dosimetric models, respectively. Conclusions This study shows that the presented compound exhibits stability in plasma and plasma protein binding very similar to memantine. Its dosimetry shows that it is suitable for use in humans due to a low total effective dose compared to other PET radiotracers.

The consumption of pesticides worldwide has been growing in recent decades, and consequently the exposure of humans and other animals to them as well. However, even though it is known that chiral pesticides can behave stereoselectively, the knowledge about the risks to human health and the environment is scarce. Among the pesticides registered to date, approximately 30% have at least one center of asymmetry, and just 7% of them are currently marketed as a pure stereoisomer or as an enriched mixture of the active stereoisomer. There are several in vitro, in vivo, and in silico models available to evaluate the enantioselective metabolism of chiral pesticides aiming ecotoxicological and risk assessment. Therefore, this paper intends to provide a critical view of the metabolism of chiral pesticides in non-target species, including humans, and discuss their implications, as well as, conduct a review of the analytical techniques employed for in vitro and in vivo metabolism studies of chiral pesticides.

Due to the potential effects of colonic metabolism, the interest in the composition and action of intestinal microbiota has increased significantly throughout the last 10 years. Recently focus is turning to the development and implementation of in vitro tools closely simulating in vivo colonic metabolic processes suitable for routine use. The aim of the present study is to compare the metabolization of the model drug sulfasalazine utilizing the novel dynamic bioreactor MimiCol and a standard static batch fermenter inoculated with cryopreserved faecal microbiota. Major advantages of the novel bioreactor MimiCol are the smaller media volume which is closer to in vivo conditions, the possibility to perform media changes and the closer simulation of in vivo mixing patterns. The study proved that the MimiCol is able to simulate the dynamic conditions found within the ascending colon. The dynamic conditions within the MimiCol led to an almost 2-fold increase of the metabolization rate constant in comparison to the static batch fermenter. Our study was able to prove that the novel dynamic bioreactor MimiCol is able to closely simulate physiologically relevant conditions.

Results gained from in vivo metabolism could be more authentic to reflect the biotransformation of drugs than in vitro metabolism. This paper discusses the development and characterization of an analytical method for controlling tiamulin (TIA) and doxycycline (DOX) residues in pig plasma and urine, as well as their in vivo biotransformation during treatment and suppression steps at pig farms. For such a purpose, urine samples were taken daily (24-hr intervals) during treatment and until day 8 after last dose. Plasma samples were collected on the last treatment day and up to days 4 and 7 after the last dose. Only traces of TIA and their metabolites have been still detected 8 days after the last day of therapy, in agreement with the period of suppression of both antibiotics set by the manufacturers in 7 days. It was estimated that TIA and DOX half-lives were of two days and one day, respectively. TIA and DOX metabolites have been identified for the first time in plasma and urine pig samples during treatment and suppression steps.

Perfluorooctane sulfonate (PFOS) found extensive use for over 60 years up until its restriction in the early 2000s, culminating in its listing under the Stockholm Convention on Persistent Organic Pollutants (POPs) in 2009. Efforts to minimise human body burdens are hindered by uncertainty over their precise origins. While diet appears the principal source for the majority of western populations (with other pathways like dust ingestion, drinking water and inhalation also important contributors); the role played by exposure to PFOS-precursor compounds followed by in vivo metabolism to PFOS as the ultimate highly stable end-product is unclear. Such PFOS-precursor compounds include perfluorooctane sulfonamide derivates, e.g., perfluorooctane sulfonamides (FOSAs) and sulfonamidoethanols (FOSEs). Understanding the indirect contribution of such precursors to human body burdens of PFOS is important as a significant contribution from this pathway would render the margin of safety between the current exposure limits and estimates of external exposure to PFOS alone, narrower than hitherto appreciated. Estimates derived from mathematical modelling studies, put the contribution of so-called “precursor exposure” at between 10% and 40% of total PFOS body burdens. However, there are substantial uncertainties associated with such approaches. This paper reviews current understanding of human exposure to PFOS, with particular reference to recent research highlighting the potential of environmental forensics approaches based on the relative abundance and chiral signatures of branched chain PFOS isomers to provide definitive insights into the role played by “precursor exposure”. Keywords: Perfluoroalkyl sulfonate, PFOS-precursors, Perfluoroalkyl substances, Biomonitoring, Human exposure, Chirality, Isomer, Body burdens

An online preconcentration approach was developed allowing the injection of very high volumes of biological samples, thereby greatly increasing sensitivity while maintaining LC resolution. The approach was applied to the analysis of radioactive samples from both in vitro and in vivo metabolism studies where typically the concentration of radioactivity given is often limited, while sample volume is usually not. The described online preconcentration approach reduces sample preparation and, therefore, also the risk for degradation and recovery issues often seen with offline preconcentration methods. In addition to facilitating the identification and profiling of low level metabolites within a sample, the described approach also provides robust quantitative analysis of samples derived from a range of biological matrices. The application of this approach is illustrated on real life samples from different matrices and containing drugs and metabolites with a wide variety in polarity, more specifically the analysis of extracts derived from an in vitro hepatocyte incubation, 36mL of blood/acetonitrile (1/1, v/v; 28dpm/mL) and 72mL of urine/methanol (9/1, v/v; 208dpm/mL).

H3R structure–activity relationships for a new class of 4,5-dihydropyridazin-3-one H3R antagonists/inverse agonists are disclosed. Modification of the 4,5-dihydropyridazinone moiety to block in vivo metabolism identified 4,4-dimethyl-6-{4-[3-((R)-2-methyl-pyrrolidin-1-yl)-propoxy]-phenyl}-4,5-dihydro-2H-pyridazin-3-one 22 as a lead candidate demonstrating potent in vivo functional H3R antagonism in the rat dipsogenia model and robust wake promoting activity in the rat EEG/EMG model.

A hydroponic experiment was conducted in the present study to investigate and compare plant uptake, translocation and metabolism of polybrominated diphenyl ethers (PBDEs) of BDE-15, BDE-28 and BDE-47 and polychlorinated biphenyls (PCBs) of PCB-15, PCB-28 and PCB-47 in maize. Root concentrations of BDE-15, BDE-28 and BDE-47 were consistently higher than PCB-15, PCB-28 and PCB-47, respectively. A significantly positive correlation was found between log RCF (root concentration factor) and log Kow of these PBDEs and PCBs, suggesting a control role of their partitioning in plant uptake. The translocation factors (TFs, Cstem/Croot) of PBDEs were generally lower than those of PCBs of the same halogen-substitutions, demonstrating easier transport of PCBs than PBDEs. Metabolites mono-, di- and tri-BDEs and PCBs were detected, suggesting the existence of in vivo metabolism of PBDEs and PCBs in maize. Dehalogenation and rearrangement of halogen atoms were identified, and some similarities but also significant differences existed between the PBDEs and PCBs. PBDEs in maize were, in general, more susceptible to metabolism compared with PCBs of the same halogen-substitutions. This is the first comparative report on the uptake, translocation and metabolism of PBDEs and PCBs in plants.

Human risk and exposure assessments require dosimetry information. Species-specific tissue dose response will be driven by physiological and biochemical processes. While metabolism and pharmacokinetic data are often not available in humans, they are much more available in laboratory animals; metabolic rate constants can be readily derived in vitro. The physiological differences between laboratory animals and humans are known. Biochemical processes, especially metabolism, can be measured in vitro and extrapolated to account for in vivo metabolism through clearance models or when linked to a physiologically based pharmacological (PBPK) model to describe the physiological processes, such as drug delivery to the metabolic organ. This review focuses on the different organ, cellular, and subcellular systems that can be used to measure in vitro metabolic rate constants and how those data are extrapolated to be used in biologically based modeling. NOTICE: The views expressed in this paper are those of the authors and do not necessarily reflect the views and policies of the U.S. Environmental Protection Agency. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

High-density lipoproteins can be separated into distinct particles based on their apolipoprotein content. In the present study, the in vivo metabolism of apoE within the apoE-containing HDL particles LpE, LpE:A-I, LpE:A-II and LpE:A-I:A-II was assessed in control subjects and in patients with abetalipoproteinemia (ABL), in whom HDL are the sole plasma lipoproteins. The metabolism of apoE within these HDL subspecies was investigated in three separate studies which differed by donor or recipient status: (1) particles purified from normolipidemic plasma and reassociated with 125I or 131I-labeled apoE injected into normolipidemic subjects (study 1); (2) particles purified from ABL plasma injected into normolipidemic subjects (study 2); and (3) particles purified from ABL plasma injected into ABL subjects (study 3). The plasma residence times (RT, hours) in study 1 were 14.3+/-2.9, 11.3+/-3.4, and 9.1+/-1.2 for apoE within LpE:A-I:A-II, LpE:A-II and LpE:A-I, respectively, while those in study 2 were 10.1+/-2.2, 9.7+/-2.4, 7.9+/-1.0 and 7.3+/-0.8 for apoE within LpE:A-I:A-II, LpE:A-II, LpE:A-I and LpE, respectively. In study 3, RTs for apoE within LpE:A-I:A-II and LpE were 8.7+/-0.9 and 6.8+/-0.9, respectively. In comparison, RT for apoA-I on LpA-I:A-II has been reported to be 124.1+/-5.5 h and that for apoA-I on LpA-I 105.8+/-6.2 h. Thus, apoE within the different apoE-containing HDL particles was metabolized rapidly and at a similar rate in control and ABL subjects. The plasma RT of apoE was longest when injected on LpE:A-I:A-II particles and shortest when injected on LpE. In summary, our data show that: (1) the plasma RT of apoE within HDL is approximately ten times shorter than that of apoA-I within HDL, and (2) apoE within HDL is metabolized at a slower rate when apoproteins A-I and A-II are present (LpE:A-I:A-II RTLpE:A-IILpE:A-ILpE). These differences were related to the lipid and apolipoprotein composition of the HDL subspecies, and, in control subjects, to the transfer of apoE from HDL subspecies to apoB-containing lipoproteins as well.

The metabolic capacities of cytochrome P 450 enzymes show wide interindividual and interracial differences. Among these enzymes, S -mephenytoin 4′-hydroxylase (CYP2C19) demonstrates a genetically determined polymorphic distribution of individual metabolizing activity in the population. The frequency distribution of the metabolic capacity of S -mephenytoin in a population shows a clear-cut bimodality and is expressed by the two phenotypes: poor metabolizers (PMs) and extensive metabolizers (EMs). The frequency of PMs in Asian populations is much higher (13% to 23%) than Caucasian populations. Moreover, there was the possibility that the frequency of PMs as well as the capacity of S -mephenytoin 4′-hydroxylation in EMs would differ within the similar ethnic populations residing in the same geographic region. A number of drugs have been investigated to determine whether their in vivo metabolism is coregulated by the same genetic factor(s) involved in the CYP2C19. Because a pronounced interracial difference in the pharmacokinetics of several drugs has been observed between PM and EM subjects, such variability may account for the interracial differences in drug responsiveness to drugs whose metabolism is regulated by the same CYP2C19-related genetic factor. In this context, the nature of the polymorphism and its possible clinical impacts for tailored-made pharmacotherapy will be discussed.

The present report is a comparative study on physico-chemical properties and metabolism of three different Lissamine-Rhodamine (LRh) derivatives of ceramide (Cer), with twelve (C12–LRh–Cer), six (C6–LRh–Cer) acyl linker spacers or with the fluorescent probe directly linked to the sphingosine moiety (C0–LRh–Cer). Transfer kinetics of the LRh–ceramides from water dispersion, albumin complex and donor vesicles to acceptor liposomes followed a double-exponential curve. Among the three ceramides, C12–LRh–Cer showed the lowest mobility. All ceramides were taken up by human fibroblasts and, with the exception of C0–LRh–Cer which was not metabolised, fluorescent sphingomyelin (SM) was the only detectable metabolite. Despite its low incorporation, C12–LRh–Cer was converted to the corresponding C12–LRh–SM with an efficiency roughly three times higher than that of C6–LRh–Cer. ‘In vitro’ enzymatic assays using cell homogenate gave similar results. These data indicate that C12–LRh–Cer is the best mimic of the natural ceramide.

Apolipoprotein A-I (apo A-I) and apolipoprotein A-II (apo A-II) represent 80 90% of the protein content of high density lipoproteins (HDL). Previously we have identified a Finnish family with an apo A-I variant (Lys107-->0) associated with reduced plasma HDL cholesterol level and decreased lipoprotein (Lp)(AI w AII) concentration compared to unaffected family members. To determine the in vivo metabolism of apo A-I and apo A-II in the carriers of apo A-I (Lys107-->0) variant we radioiodinated normal apo A-I with 125I and apo A-II with 131I and compared the kinetic data of two heterozygous apo A-I(Lysl07-->0) patients (HDL cholesterol leves 0.31 and 0.69 mmol/l) to that of eight normolipidemic, healthy control subjects. Plasma radioactivity curves of 125I-labelled normal apo A-I of the patients demonstrated accelerated clearance of apo A-I compared to control subjects. In the two patients the fractional catabolic rates (FCR) of apo A-I were 0.347/day and 0.213/day, respectively, while the mean FCR of apo A-I of the control subjects was 0.151 +/- 0.041/day. Similarly, the plasma decay curves of the 131I-labelled apo A-II showed more rapid clearance of apo A-II in the two patients than in control subjects. The FCR of apo A-II in the two patients were 0.470/day and 0.234/day, while the mean FCR of apo A-II in control subjects was 0.154 +/- 0.029/day. The calculated production rates of apo A-I were similar in patients and in control subjects, and the production rates of apo A-II were significantly higher in patients than in control subjects. Our results show that the Lp(AI w AII) deficiency in patients with the apo A-I(Lys107-->0) is associated with increased fractional catabolic rates of normal apo A-I and apo A-II, while the production rates of these apolipoproteins are normal (apo A-I) or slightly increased (apo A-II).

Certain synthetic metalloporphyrins have been shown to mimic the in vivo metabolism of some pharmaceuticals. Oxidation, hydroxylation and N-demethylation yielded synthetic metabolites. If found to be general, this lays the foundation of a predictive basis to optimize analog design of inhibitors with reduced oxidative reactivity, to determine the proclivity of drugs to form biologically active metabolites and provides a convenient methodology for their preparation.

The biomimetic potential of metalloporphyrin catalysts has been studied using nicotine as the substrate. Results indicate the formation of products identical to those obtained from in vivo metabolism.

On the basis of extensive information on in vivo metabolism as well as biomimetic reactions using simple SH compounds and some enzymes, numerous chemical functions which react with SH groups are divided into two classes; i.e., one which involves electrophilic addition (EA) to an SH group and the other which features displacement reactions (DR) by the SH group (see Tables 1 and 2). The known tumor inhibitors are accordingly classified into EA and DR types. Biomimetic reactions of tumor inhibitors with model compounds of SH enzymes (or coenzymes) and with some SH enzymes themselves are described. Finally, as enhancement factors for the antitumor activity, the roles of hydrogen-bonding, neighboring group participation, and effect of ester side chains are introduced. These discussions may serve in the development of the new SH alkylating antitumor agents.

1. 1. After 4hr of the intraperitoneal injection of different doses of (R)-[5-14C]mevalomc acid (MVA), its incorporation into nonsaponifiable and saponifiable lipids was maximal in neonatal chick kidneys and liver, and minimal in brain, spinal cord and skin. 2. 2. Using 14CO2 production from [5-14C]MVA as an index of the shunt pathway not leading to sterols, we have demonstrated for the first time that about 11% of MVA was in vivo metabolized by this pathway in nonmammalian species. 3. 3. Kidneys presented the maximal ability to incorporate MVA into nonsaponifiable and saponifiable lipids at any time considered (15–750 min). The percentage of radioactivity recovered as saponifiahle lipids in liver and kidney decreased after 12 hr the injection of MVA. 4. 4. Although the absolute amounts of 14C incorporated in both derivatives were much less in brain. spinal cord and skin than in liver and kidneys, the relative percentages found in the saponifiable fraction were clearly higher in the former tissues, especially in the spinal cord.

The in vivo metabolism of sulfogalactosyl glycerolipids (SGG) was studied in the cerebrum and cerebellum of developing mice after intraperitoneal injection of [35S]sulfate. After correction for the specific radioactivity changes of blood sulfate the quantitative rates of biosynthesis and biodegradation of this lipid could be determined. In addition, the net accumulation of SGG was measured. Throughout development the rates of SGG biosynthesis and net accumulation were higher in the cerebellum than in the cerebrum. The developmental patterns of SGG net synthesis in both parts of the brain were closely related to those observed earlier for sulfatide. During development the rate of SGG biosynthesis in both parts of the brain showed a peak earlier than that of sulfatide (at 14 days versus 20 days). The in vivo patterns of SGG degradation followed those of biosynthesis in the cerebrum and cerebellum. During postnatal development 40 to 80% of the daily synthesized SGG disappeared within 24 hr, suggesting that degradation may also be involved in the regulation of SGG net synthesis during myelination, as previously indicated for sulfatide.

Five - 20 nmoles of [5,6,8,9,11,12,14,15-3H8]leukotriene C4 was injected into three male volunteers. Forty-eight percent of the administered 3H was recovered from urine and 8% from feces, within a 72 hr period. Of the total urinary radioactivity 44% was excreted during the first hour after injection. This activity was mainly found in one compound, designated "I". The radioactivity excreted into urine later than one hour after injection, consisted partly of Compound I and two additional components, and partly of polar, non-volatile material. Compound I was identified as leukotriene E4 by UV-spectroscopy and cochromatographies in three high performance liquid chromatography systems with synthetic reference compounds. A total of 13% of administered radioactivity was excreted in urine as leukotriene E4.

7 beta, 17-Dimethyltestosterone (17 beta-hydroxy-7 beta, 17-dimethyl-4-androsten-3-one) (I) was given to three subjects in oral doses of 400 mg per day for ten days. The initial dose contained the steroid tritiated in the 6 and 7 positions. Plasma levels and urinary excretion patterns were followed in all three subjects. Isolations were done on the urine, plasma, and stools of one patient. From the urine 7 beta, 17-dimethyl- 5 alpha-androstane-3 beta,17 beta-diol (VI) was isolated from the nonhydrolyzed fractions. Unchanged (I), 7 beta,17-dimethyl-5 beta-androstane-3 alpha,17 beta-diol (III) and 7 beta, 17-dimethyl-5 beta-androstane-3 beta,17 beta-diol (IV) were isolated from the nonhydrolyzed and enzyme-hydrolyzed fractions. 7 beta,17-dimethyl-5 alpha-androstane-3 alpha,17 beta-diol (V) was isolated from the enzymatic fractions. From the stools were isolated unchanged (I), (III), (IV), (V), and (VI). Unchanged (I) and its 5 alpha-dihydro derivative (17 beta-hydroxy-7 beta,17-dimethyl-5 alpha-androstan-3-one) (II) were identified in the plasma. The total recovery of radioactivity in the one patient on whom the isolations were done was 57%; 40% from the urine and 17% from the stools.

The roles of the sterol and nonsterol pathways in the metabolism of circulating mevalonate have been estimated in the intact rat. On an average, the sterol pathway accounts for 74 per cent of the mevalonate metabolized, while the nonsterol, or shunt, pathway is responsible for 26 per cent of the mevalonate metabolized in the whole animal. The contribution of the kidneys to each of these processes was evaluated by two approaches. First, the localization of labeled sterols and sterol precursors derived from [14C]mevalonate was determined in each of the major tissues of the body and, second, the effect of nephrectomy upon mevalonate metabolism by the sterol and shunt mechanisms was examined. The results confirm our earlier conclusion that the kidneys represent the primary tissue site of conversion of circulating mevalonate to sterols and sterol precursors. In the present study, it was shown that by 6 h after administration of [14C]mevalonate, the major end product of mevalonate metabolism in the kidneys is cholesterol and that, moreover, the kidneys are responsible for most of the cholestreol synthesized in the intact animal from injected mevalonate. Following nephrectomy, the extrarenal tissues can readily assume the dominant role normally played by the kidneys in synthesizing cholesterol and other sterols from circulating mevalonate. The major observation of the present study is that the kidneys represent the primary site of mevalonate metabolism by the shunt pathway, in that nephrectomy results in approximately a 60 per cent decrease in the mevalonate metabolized by the shunt pathway. These studies, therefore, reinforce and expand the evidence that the kidneys represent the most important single tissue site for the metabolism of circulating mevalonate.

Lead was administered to Long-Evans rats by daily oral gavage for 30 days at doses of 200, 400, or 600 mg lead/kg/day. The rats were then administered one of the radiolabeled insecticides and the metabolic products examined. The lead-treated rats had blood lead concentrations of ca. 200 μg/dl in the 200 mg/kg/day group and ca. 475 in the 400 mg/kg/day group. Concentrations of lead in the femur were 500 μg/g or higher. Despite this high body burden of lead (accompanied by a 30% weight deficit at 600 mg/kg/day), no difference in the rate of elimination of radiolabeled material was observed. Furthermore, the lead treatments did not change the relative proportions of the detected metabolites. Thus, despite the known effects of lead on heme synthesis, these treatments had no detectable effect in vivo on the metabolism of propoxur or malathion.

In rats 80 to 95% of 4'-deoxypyridoxine administered intraperitoneally, intravenously, intramuscularly, or subcutaneously was excreted in the urine within 7.5 hours. Orally administered deoxypyridoxine was also rapidly eliminated. Over one-half of the excreted material appeared as deoxypyridoxine-3-(hydrogen sulfate) and the remainder as unchanged deoxypyridoxine. Tissue concentrations of deoxypyridoxine 5'phosphate were comparable to those of pyridoxal 5'phosphate. In normal men about 50% of a single oral dose (3 to 7.5 mg/kg of body weight) appeared in the urine within 6 hours. 4'Deoxy-5-pyridoxic acid accounted for 50 to 100% of the excreted material. The remainder was unchanged deoxypyridoxine. No deoxypyridoxine-3-(hydrogen sulfate) was detected in human urine and no 4'-deoxy-5-pyridoxic acid was found in rat urine. Deoxypyridoxine 5'-phosphate was not detected in the urine of either species. The complexity of deoxypyridoxine metabolism indicated by these data suggests the use of caution in extrapolating data obtained with deoxypyridoxine to B6 metabolism in the absence of deoxypyridoxine, and particularly in extrapolating results from the rat to man. Synthesis for 4'-deoxypyridoxine-3-(ethyl carbonate), 4'-deoxypyridoxine 5'-acetate, 4'-deoxy-3-0-(2-sulfoethyl)-pyridoxine, and the metabolites are presented. These synthesis were facilitated by using ethylchloroformate conjugates and N-methylpiperazine hydrolysis to block and unblock the phenol group.

The in vivo metabolism of phenthoate ( O,O -dimethyl S -[α-(carboethoxy)benzyl]phosphorodithioate) was followed in rats after oral administration of a nontoxic dose of 100 mg/kg. The same metabolic study was conducted following coadministration of 0.5% O,S,S -trimethyl phosphorodithioate (OSS-Me). When administered alone, phenthoate was metabolized principally by carboethoxy ester hydrolysis and cleavage of the PO and CS bonds, resulting in at least six metabolites. The primary urinary metabolite excreted was phenthoate acid. Coadministration of 0.5% OSS-Me did not alter the types of metabolites excreted. However, a reduction of the carboxylesterase-catalyzed product (phenthoate acid) was observed, indicating that the enzyme responsible for the major pathway of phenthoate detoxication was inhibited. Alternate detoxication processes did not compensate for the reduction in carboxylesterase-catalyzed detoxication. It was concluded that inhibition of the carboxylesterase enzymes is the major cause of the potentiation of phenthoate toxicity by OSS-Me.

The effects of codfish insulin (2 IU/kg) on 14C-glucose and 14C-glycine metabolism in vivo were studied in cannulated Northern pike (Esox lucius L.). Insulin significantly reduced plasma glucose levels and increased the incorporation of 14C-glucose carbon into liver and muscle lipid and muscle protein, and of 14C-glycine carbon into muscle protein. These results suggest that the metabolic role of insulin in pike is similar to that observed in mammals.

Metabolic rates of mescaline (3,4,5-trimethoxy-β-phenylethylamine) and of its non-hallucinogenic isomer, 2,3,4-trimethoxy-β-phenylethylamine were studied in whole and in different areas of mouse brain in vivo . The effects of Pargyline and of Probenecid on the concentrations of the amines and their corresponding metabolites, together with the results obtained from intraventricular injections of mescaline suggested the formation of the trimethoxyphenylacetic acids in the brain. The metabolic differences between mescaline and 2,3,4-trimethoxy-β-phenylethylamine are discussed in terms of possible implications of metabolic parameters with psychotomimetic activity.

Radioactive oleic and linoleic acids, labeled with 3H in the chain and 14C in the carbonyl group, were administered to white leghorn laying hens. Mixtures fed in separate experiments included: (1) 3H- and 14C-labeled oleic acid, (2) 3H-and 14C-labeled linoleic acid and (3) [3H] oleic acid and [14C] linoleic acid. The 3H/14C ratios of both the neutral lipid and phospholipid fractions from the egg yolk and of the isolated acids from these lipid fractions were compared to that in the administered mixture. Agreement in the 3H/14C ratios for the neutral lipid fraction from each of the feeding experiments indicated that neither the 3H- and 14C labeled acids nor the oleic or linoleic acids were distinguishable during synthesis of the neutral lipid. Analysis of the phospholipid fractions showed that when dual-labeled mixtures of oleic acid were administered, 3H/14C ratios were elevated and, therefore, there was selective elimination of the 14C label. When dual-labeled mixtures of linoleic acid were administered, the 3H/14C ratios were in agreement; and when the two acids were administered simultaneously as a dual-labeled mixture, there was selective incorporation of linoleic acid. These findings indicate separate metabolic pathways for synthesis of neutral lipid and phospholipid in egg yolk as expected, as well as preferential use of the essential fatty acid in the phospholipid by the hen.

A critical literature review summarizes and discusses information concerning the role of carnitine in the oxidation of long-chain fatty acids and other areas of in vivo metabolism. Dietary and endogenous sources of carnitine are described, as well as its transport and homeostasis. Attention also is given to: potential causes of cellular carnitine deficiency and the consequences of impaired carnitine function; primary congenital carnitine metabolic disorders; the potential carnitine insufficiency of vegetarians; and human studies of the characteristics of a variety of non-congenital carnitine-deficient clinical states.(wz)

In vivo metabolism and biliary excretion of PAH by brown bullheads was determined using an HPLC/fluorescence method. In laboratory studies, 24 hours after feeding of PAH, bullheads had evidence for polar metabolites of the PAH in their bile as detected by HPLC’/fluorescence. These materials were detectable only at wavelengths specific for the compound that was fed. Analysis of bile from wild bullheads collected from areas with varying degrees of pollution demonstrated that bullheads from the Buffalo River had benzo[a]pyrene equivalents that were 7–148 times greater than those found in fish from less polluted areas. Similarly, levels of phenanthrene equivalents were 7–297 times greater in Buffalo River fish when compared to the other sites. These studies indicate that bullheads can rapidly metabolize dietary PAH, and wild bullheads from industrially impacted waterways such as the Buffalo River are receiving significant PAH exposure. This PAH exposure may account, in part, for the increased incidence of neoplasia observed in the bullheads.

This communication describes a surgical preparation of experimental animals to permit NMR spectroscopic studies of the metabolism of internal organs. In the procedure developed, the layer of protective muscle directly above the organ is removed, but the skin is left intact. NMR studies of the metabolism of the organ can then be carried out using surface coils placed externally over the herniated area. Modified probe and stack designs for use with the surgically modified animals in a conventional NMR spectrometer are described. Phosphorus-31 NMR spectra of liver and kidney of the modified animals have been obtained, and data corresponding to the hepatic response to a load of fructose are presented.

Whole body autoradiograms of mice injected with 2,2′,3,3′,6-[14C]-pentachlorobiphenyl (I), 2,3,3′,4′,6-[14C] pentachlorobiphenyl (II), 2,2′,3,5′,6-[14C] pentachlorobiphenyl (III) and 2,3′,4,5,5′-[14C] pentachlorobiphenyl (IV) showed a specific accumulation of I–III in the lung parenchyma, whereas IV did not accumulate in the lung tissue. The results suggest that chlorobiphenyls with chlorine atoms in the positions 2,3,6 possess a specific affinity for the lung parenchyma. These chlorobiphenyl differ in chemical structure from those which are accumulated in the bronchial mucosa and those which are not taken up in the respiratory tract. The importance of in vivo metabolism in the determination of structure activity relationships is stressed.

Administration of either all-trans-[3H]- or 13-cis-[3H]retinoic acid to hamsters fed a normal diet results in the formation of a number of polar metabolites. At least one of these metabolites has been shown to be common to both isomers of retinoic acid and can be generated in a hamster liver 10,000 X g supernatant system using 13-cis-retinoic acid as substrate. It has been identified as 13-cis-4-oxoretinoic acid by mass spectral, ultraviolet absorption, and proton NMR characteristics, as well as by its co-migration with synthetic 13-cis-4-oxoretinoic acid in two different high pressure liquid chromatographic systems. In addition, its metabolic precursor, 13-cis-4-hydroxyretinoic acid, has been tentatively identified. These compounds are believed to be early metabolites in the elimination pathway of retinoic acid from the body.

Mevalonic acid exists in two forms at physiologic pH: an open-chain salt and a cyclic lactone. Studies by others have demonstrated preferential utilization of the salt by the brain and of mevalonolactone by isolated hepatocytes. The major finding of this report is the presence of a very active deltalactonase in rat serum which rapidly converts mevalonolactone into the open-chain salt. Studies showed that the female rat oxidized 92 nmol of [5-14C]mevalonic acid salt or lactone to CO2 in 7 h, while the male oxidized only 52 nmol of either form of the injected mevalonate. There was no statistical difference in the in vivo metabolism of the salt or lactone. When mevalonolactone (0.1 mM) was incubated in neat rat serum for 20 sec, more than 82% of the lactone was converted to the salt as compared to 8% in heat-inactivated serum. These observations demonstrate for the first time the presence of a heat-labile delta-lactonase (possibly mevalonolactone hydrolase) in rat serum.

There is a growing body of evidence that apoproteins of the high density lipoproteins (HDL) exchange between lipoprotein particles through the aqueous phase and that there is always a finite but physiologically important quantity of lipid-free apoprotein in plasma. We have studied the theoretical consequences of this concept on the catabolism of apoproteins and developed a testable model for studying the in vivo metabolism of HDL apoproteins. This model describes the putative modification of the apparent tissue distribution spaces of the apoprotein that would result from a change in the partitioning of this apoprotein between HDL and the aqueous phase. The main parameters predicted by the model include the tissue distribution spaces of free monomeric apoprotein, those of HDL-bound apoprotein and the partition coefficient of the apoprotein between HDL and the aqueous phase in blood. We have designed several ways of testing this model in vivo including the use of model synthetic apoproteins. This model can be generalized to a number of other binding systems.

Three double-labeled ceramides, [1-14C]lignoceroyl D-erythro-[1-3H]sphingosine, [1-14C]palmitoyl D-erythro-[1-3H]sphingosine and D-[1-14C]cerebronoyl D-erythro-[3-3H]-sphingosine, were prepared and injected separately into the brains of 18-day-old rats. The animals were killed after 2 h and various sphingolipids were isolated and purified. These lipids were further fractionated into subgroups depending on their fatty acid content (nonhydroxy or alpha-hydroxy, shorter chain or longer chain), 3H/14C ratios obtained in ceramides, cerebrosides, and sphingomyelins containing different fatty acids from the injected material were much higher than the initial ratio. This observation indicates that a replacement of the fatty acid occurred in the injected ceramide. Comparison of the 3H/14C ratios of the cerebrosides and sphingomyelin in a specific fatty acid group with the ratios of the corresponding ceramide indicated that most of these lipids were derived directly from the ceramide. The 3H/14C ratio of the hydroxycerebroside obtained from cerebronyl sphingosine-injected brain was nearly twice the ratio of the injected material. In addition to these lipids, considerable radioactivity was incorporated into an unknown nonpolar material in the brains which had been injected with [1-14C]lignoceroyl or [1-14C]palmitoyl [1-3H]sphingosine. This material was tentatively identified as ceramide fatty acid ester. The 3H/14C ratio of the ester was identical to that of the injected material.

Following intraperitoneal administration, 5-methoxy-N,N-dimethyltryptamine and N,N-dimethyltryptamine are subject to both a very rapid uptake into, and clearance from, all tissues examined. The current studies in vivo confirm previous in vitro observations that the routes involved in the metabolism of these compounds include oxidative deamination, N-demethylation, O-demethylation, and N-oxidation. The analysis of metabolic profiles in various tissues led to the identification of the N-oxides as major metabolites. The successful inhibition and redirection of metabolism away from the indole acids towards the parent compounds and their structurally unique metabolites were demonstrated in animals pretreated with iproniazid.

The in vivo metabolism of dextrosulphenidol has been studied using various test organisms. Differences are noted and comparisons are made as to the effect of biological variation on the absorption, distribution, and excretion of the drug.

Summary Δ 1 ,6β-hydroxy-17α-methyltestosterone was isolated from the urine of a patient after administration of Δ 1 ,17α-methyltestosterone. Another metabolite, in which ring A appears not to have been metabolized, was isolated but not as yet finally identified.