Dimethyluric Acid Research Articles

Combining metabolomics and machine learning to discover biomarkers for early-stage breast cancer diagnosis.

There is an urgent need for better biomarkers for the detection of early-stage breast cancer. Utilizing untargeted metabolomics and lipidomics in conjunction with advanced data mining approaches for metabolism-centric biomarker discovery and validation may enhance the identification and validation of novel biomarkers for breast cancer screening. In this study, we employed a multimodal omics approach to identify and validate potential biomarkers capable of differentiating between patients with breast cancer and those with benign tumors. Our findings indicated that ether-linked phosphatidylcholine exhibited a significant difference between invasive ductal carcinoma and benign tumors, including cases with inconsistent mammography results. We observed alterations in numerous lipid species, including sphingomyelin, triacylglycerol, and free fatty acids, in the breast cancer group. Furthermore, we identified several dysregulated hydrophilic metabolites in breast cancer, such as glutamate, glycochenodeoxycholate, and dimethyluric acid. Through robust multivariate receiver operating characteristic analysis utilizing machine learning models, either linear support vector machines or random forest models, we successfully distinguished between cancerous and benign cases with promising outcomes. These results emphasize the potential of metabolic biomarkers to complement other criteria in breast cancer screening. Future studies are essential to further validate the metabolic biomarkers identified in our study and to develop assays for clinical applications.

Abstract 2344: Shotgun metabolomics revealed possible reprogrammed pathways that shift for cancer development in non-alcoholic steatohepatitis

Abstract Purpose: The future prevalence of hepatocellular carcinoma (HCC) is expected to become further divergent with the emergence of non-alcoholic steatohepatitis (NASH) as a major contributor. Multiple etiologies are associated with the development of HCC each is characterized by specific pattern of metabolic dysregulations. The identification of the metabolic readouts that function in pathways reprograming for HCC development from NASH is still far from clear. Materials and Methods: Well diagnosed Sixty-one patients were recruited. They were divided into thirty-one NASH patients and thirty HCC patients developed from NASH (HCC-NASH) based on biochemical, hematological parameters and on serum levels of alpha-fetoprotein and other clinical characteristics, radiological and histological analysis. Fasting serum samples were screened for the metabolic profile of NASH and HCC-NASH patients using LC-MS/MS Triple TOF. Subsequently, multivariate data analysis, machine learning, receiver-operating curves and ingenuity pathway analysis were conducted to explore the metabolic signature that could robustly determine the causative metabolite which function for understanding, predicting and targeting HCC in NASH patients. Results: Our study showed a panel of thirty metabolites completely segregating HCC-NASH from NASH patients at folds change >2. Of these small molecules, some were positively associated with HCC in NASH patients including L-carnitine, 2-methylglutaric acid, adipic acid, serotonin, gamma- and alpha linolenic acid, L-alloisoleucine, L-arginine, N-methyl-L-glutamic Acid, pyroglutamic acid, (R)-salsolinol, L-histidine, progesterone, 1,9 and 1,3 -dimethyluric acid, citrulline, N-acetyl-L-methionine, D-malic acid, clupanodonic, cortisone and L-octanoylcarnitine. On the other side, daidzein, 5'-methylthioadenosine, L-lysine, niacinamide, L-aspartic acid, genistein, guanosine, 5- hydroxyeicosatetraenoic and naringin were negatively associated with the development of HCC in NASH patients. The area under the receiving operating curve showed that our pattern of metabolites has a predictive power of 90%. These metabolites function in specific pathways perpetuation most importantly related to the transport of bile salts and organic acids, metal ions and amine compounds, fatty acid metabolism, tricarboxylic acid cycle, neurotransmitter clearance, metabolism of serotonin and proline catabolism. Alternatively, gluconeogenesis, purine salvage, phenylalanine metabolism, and sirtuin 1 negatively regulates rRNA expression were significantly downregulated in HCC-NASH as compared to NASH patients. Conclusion: This study provided for the first time a specific pattern of metabolites with a detailed map for the most predominant perpetuated metabolic pathways that could understand, predict and target HCC development from NASH. Citation Format: Marwa O. El-Derany, Eman Ahmed, Ali M. Anwar, Sameh Magdeldin. Shotgun metabolomics revealed possible reprogrammed pathways that shift for cancer development in non-alcoholic steatohepatitis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2344.

Plasma Metabolome and Lipidome Associations with Type 2 Diabetes and Diabetic Nephropathy.

We conducted untargeted metabolomics analysis of plasma samples from a cross-sectional case–control study with 30 healthy controls, 30 patients with diabetes mellitus and normal renal function (DM-N), and 30 early diabetic nephropathy (DKD) patients using liquid chromatography-mass spectrometry (LC-MS). We employed two different modes of MS acquisition on a high-resolution MS instrument for identification and semi-quantification, and analyzed data using an advanced multivariate method for prioritizing differentially abundant metabolites. We obtained semi-quantification data for 1088 unique compounds (~55% lipids), excluding compounds that may be either exogenous compounds or treated as medication. Supervised classification analysis over a confounding-free partial correlation network shows that prostaglandins, phospholipids, nucleotides, sugars, and glycans are elevated in the DM-N and DKD patients, whereas glutamine, phenylacetylglutamine, 3-indoxyl sulfate, acetylphenylalanine, xanthine, dimethyluric acid, and asymmetric dimethylarginine are increased in DKD compared to DM-N. The data recapitulate the well-established plasma metabolome changes associated with DM-N and suggest uremic solutes and oxidative stress markers as the compounds indicating early renal function decline in DM patients.

Characteristic of Metabolic Status in Heart Failure and Its Impact in Outcome Perspective.

Metabolic alterations have been documented in peripheral tissues in heart failure (HF). Outcomes might be improved by early identification of risk. However, the prognostic information offered is still far from enough. We hypothesized that plasma metabolic profiling potentially provides risk stratification for HF patients. Of 61 patients hospitalized due to acute decompensated HF, 31 developed HF-related events in one year after discharge (Event group), and the other 30 patients did not (Non-event group). The plasma collected during hospital admission was analyzed by an ultra-high performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOFMS)-based metabolomic approach. The orthogonal projection to latent structure discriminant analysis (OPLS-DA) reveals that the metabolomics profile is able to distinguish between events in HF. Levels of 19 metabolites including acylcarnitines, lysophospholipids, dimethylxanthine, dimethyluric acid, tryptophan, phenylacetylglutamine, and hypoxanthine are significantly different between patients with and without event (p < 0.05). Established risk prediction models of event patients by using receiver operating characteristics analysis reveal that the combination of tetradecenoylcarnitine, dimethylxanthine, phenylacetylglutamine, and hypoxanthine has better discrimination than B-type natriuretic peptide (BNP) (AUC 0.871 and 0.602, respectively). These findings suggest that metabolomics-derived metabolic profiling have the potential of identifying patients with high risk of HF-related events and provide insights related to HF outcome.

Alterations of Proximal Tubular Secretion in Autosomal Dominant Polycystic Kidney Disease.

In autosomal dominant polycystic kidney disease (ADPKD), the GFR often remains normal despite significant nephron loss. Proximal tubular secretory clearance may be reduced in ADPKD before detectable changes in GFR. We used targeted mass spectrometry to quantify secretory solutes from blood and urine samples from 31 patients with ADPKD and preserved GFR (mean eGFR =111±11 ml/min per 1.73 m2) and 25 healthy control individuals as well as from 95 patients with ADPKD and reduced GFR (mean eGFR =53±21 ml/min per 1.73 m2) and 92 individuals with non-ADPKD CKD. We used linear regression to compare the fractional excretion of each solute between ADPKD and control groups. Among 112 patients with ADPKD, we used linear regression to determine associations of solute fractional excretion with height-adjusted total kidney volume. After adjusting for demographics, clinical characteristics, and kidney function measures, the fractional excretions of three secretory solutes were lower in patients with ADPKD and preserved GFR compared with healthy individuals: 52% lower cinnamoylglycine excretion (95% confidence interval, 24% to 70%), 53% lower tiglylglycine excretion (95% confidence interval, 23% to 71%), and 91% lower xanthosine excretion (95% confidence interval, 83% to 95%). In addition to lower excretions of tiglylglycine and xanthosine, patients with ADPKD and reduced GFR also demonstrated 37% lower dimethyluric acid excretion (95% confidence interval, 21% to 50%), 58% lower hippurate excretion (95% confidence interval, 48% to 66%), 48% lower isovalerylglycine excretion (95% confidence interval, 37% to 56%), and 31% lower pyridoxic acid excretion (95% confidence interval, 16% to 42%) compared with patients with non-ADPKD CKD and comparable eGFR. Among patients with ADPKD, solute fractional excretions were not associated with differences in kidney volume. Patients with ADPKD and preserved and reduced GFR demonstrate lower tubular secretory solute excretion compared with healthy controls and patients with non-ADPKD CKD. Our results suggest that tubular secretion is impaired in ADPKD independent of GFR.

Effects of gender on ketamine-induced conditioned placed preference and urine metabonomics

ObjectiveThe aim of this study was to examine whether or not there was a gender difference in CPP (conditioned placed preference) induced by ketamine and to further explore the effect of sex on metabolic responses to ketamine inducing in SD rats. Methods: We measured ketamine-induced conditioned place preference and ketamine-induced metabolic changes in urine by using 1H nuclear magnetic resonance (NMR) coupled with principal component analysis (PCA), partial least squares (PLS) and orthogonal signal correction (OSC) analysis. Results: In the CPP experiment, ketamine served as a positive reinforcing agent in both male and female rats, but, in particularly, the preference score of female rats was significantly higher than that of male rats. Compared with male rats, the metabolic trajectory fluctuation of the female rats was relatively larger. At the same time, different metabolites (1, 3-dimethyluric acid, cysteine-S-sulfate, glyceraldehydes, glycine, ribitol, acetoacetic acid, creatine, 3-methyladenine, hypotaurine, taurine, dimethylglycine and theobromine) between male and female rats were found. Conclusions: Female Sprague-Dawley rats were more sensitive to the ketamine-induced CPP than male rats. The fluctuation ranges of metabolic trajectory and metabolite contents in urine were both different between female and male rats. This would provide targeted suggestions for ketamine abuser, for example, men and women should take different drug withdrawal therapeutic methods.

Effects of plasma albumin on theophylline concentration in lung tissue

To study the relationship between plasma and lung tissue theophylline concentrations, we changed the number of binding sites for theophylline on serum albumin. Cefazoline, which competes with theophylline for those binding sites, was given to rats, and free theophylline was separated by ultrafiltration. The dose of cefazoline was directly related to the percentage of free theophylline and was inversely related to the plasma total theophylline concentration. The plasma free theophylline concentration, however, was unchanged at the lower doses of cefazoline and was low only at the highest dose. The concentration of theophylline in lung tissue was inversely related to the dose of cefazoline. The concentration of 1, 3-dimethyluric acid, a major metabolite of theophylline, was also inversely related to the dose of cefazoline, which suggests that the metabolic rate of theophylline did not increase. Excretion of theophylline via the urine might be accelerated by its diuretic action. We conclude that when the binding of theophylline to plasma proteins is altered in rats, the concentration of free theophylline in plasma does not reflect the concentration of theophylline in lung tissue. Instead, the total theophylline concentration in plasma can be used as an index of the concentration in lung tissue.

Effect of low-dose macrolide antibiotics on theophylline disposition in pediatric patients

Low-dose macrolide antibiotics are administered for the treatment of certain chronic inflammatory sinopulmonary diseases (e.g., sinusitis and panbronchiolitis). Because 14-membered ring macrolide antibiotics administered at antimicrobial doses have been suggested to elicit a significant inhibitory effect on the hepatic metabolism of theophylline, we studied whether low-dose macrolide antibiotic therapy also evokes a clinically relevant alteration in the disposition of theophylline. The steady-state serum theophylline concentration and the urinary concentrations of theophylline and its metabolites [i.e., 1-methyluric acid (1MU), 3-methylxanthine (3MX), 1, 3-dimethyluric acid (DMU), and caffeine] were examined in nine stable asthmatic children who received both theophylline and lowdose erythromycin or clarithromycin (12.3±4.5mg/kg body weight/day) and in ten children who received theophylline alone.An immunoassay and high-performance liquid chromatography with ultraviolet detection (HPLC-UV) were used for serum and urinary drug assay, respectively. Results demonstrated no significant differences in serum theophylline concentration, the metabolic clearance of theophylline to its metabolites, and the renal clearance of theophylline between the two groups. In conclusion, the administration of low-dose macrolide antibiotics for the treatment of sinopulmonary diseases would not stipulate a dosage reduction of concomitantly administered theophylline in pediatric patients

Is Pediatric Labeling Really Necessary?

Labeling refers to the label on the drug container and all printed materials, including the package insert, that accompanies the product. Labeling of a drug indicates that there is substantial evidence from adequate and well controlled clinical trials for the safe and effective use of that drug. Labeling provides important information on clinical pharmacology, indications and usage, contraindications, precautions, adverse effects, dosage, and administration. Unfortunately for children, most drug labeling contains the precautionary disclaimer, because safety and efficacy in children have not been established. The availability of safe and effective drugs has been directly responsible for the improvement in health over the past 50 years. Children essentially have been excluded from the benefit of the many therapeutic advances that have marked pharmaceutic drug development. The failure to include children in clinical trials during drug development leads to delay in implementing potentially effective treatment. Most US food and Drug Administration-approved drugs lack approval for use in all children or are restricted to certain pediatric age groups, primarily older children.1 Only a few of the new drugs released in this country each year are approved for use in children. This lack of information on the safe and effective use of drugs in the most vulnerable patients, infants and neonates, is of greatest concern. Only five of the 80 most frequently used drugs have been approved for use in this population. Another problem is that most drugs are not available in suitable pediatric dosage forms. They are not available in appropriate dosage sizes, lack liquid formulation, and taste peculiar to the child, making compliance difficult. Pharmacies extemporaneously prepare many drugs in liquid dosage forms for use in children. These dosage forms are not sufficiently tested to determine stability, efficacy, or expiration dating. For solid dosage forms, parents often must divide adult tablets …

Elimination of theophylline metabolites in healthy adults

The metabolism of theophylline (TP) (540 mg per os) was determined by measuring plasma and saliva concentrations of TP and its metabolites, 0–24 h after loading, and urinary excretion 0–48 h after loading. TP and its five metabolites were separated and quantified by combining high-performance liquid chromatography and capillary electrophoresis. In addition to TP, 1,3-U, 3-X and 1-U were consistently found in plasma and saliva. The area under the plasma concentration-time curve (AUC) showed that TP accounted for 91±4% (mean+SD) of the total AUC in plasma with 1,3-U accounting for 3.1±1.4%, 3-X for 3.4±1.8% and 1-U for 2.5±1.5%. The urine analyses showed that unchanged TP accounted for 19±5% of total excretion, the remainder being 1, 3-dimethyluric acid (1,3-U, 41±6%), 1-methylxanthine (1-X, 2±0.8%), 1-meth-yluric acid (1-U, 26±6%), 3-methyxanthine (3-X, 11 ±3%) and 3-methyluric acid (3-U, 1±0.3%). Highest excretion rates were observed for 1,3-U (70±29 umol/ h), 1-U (40±26 μmol/h) and 3-X (20±15 μmol/h) 6–9 h after TP ingestion suggesting the high excretion of 1,3-U, 1-U and 3-X by the kidneys. The highest excretion rate of TP (50±8 μmol/h) occurring at 0–6 h after the load and rapidly declining thereafter, indicated the lower excretion of TP compared with its metabolites. N3-demethylation of TP accounted for 34±6% of the urinary metabolites, N1-demethylation of TP for 15±3% and C8-oxidation of TP for 51±9%. C8-oxidation of 1-X and 3-X was 93±4% and 9±4%, respectively, of the excreted amount of monomethylxanthine plus formed monomethylurate. Since the extent of all metabolic reactions remained constant during the load, it is suggested that TP is metabolized by hepatic reactions that occurred simultaneously and not sequentially.

Elimination of theobromine metabolites in healthy adults.

The metabolism of theobromine (TB) (500 mg per os) was determined by measuring plasma and saliva concentrations of TB and its metabolites 0-24 h after the load, and urinary excretion 0-48 h after the load. TB and its six metabolites were separated and quantified by combining high performance liquid chromatography and capillary electrophoresis. The urine analyses showed that unchanged TB accounted for 21 +/- 4% (mean +/- SD) of total excretion, the remainder being 7-methylxanthine (7-X, 36 +/- 5%), 3-methylxanthine (3-X, 21 +/- 4%), 6-amino-5[N-methylformylamino]-1-methyluracil (6-AMMU, 11 +/- 4%), 7-methyluric acid (7-U, 10 +/- 2%), 3,7-dimethyluric acid (3,7-U, 1.3 +/- 0.6%) and 3-methyluric acid (3-U, 0.5 +/- 0.4%). In addition to TB, 7-X and 3-X were consistently found in plasma and saliva; 6-AMMU and 7-U were found in plasma and saliva at concentrations < or = 2 mumol l-1 and 0.2 mumol l-1, respectively. TB concentrations in plasma and saliva were similar, whereas the saliva concentrations for 7-X and 3-X were found to be 63 +/- 17% of the plasma concentrations for 7-X and 74 +/- 13% for 3-X, respectively. The high urinary-to-plasma concentration ratio of 7-U (200-300) suggests high excretion of 7-U by the kidneys. Excretion of 7-X, 3-X and 6-AMMU was also high (urinary-to-plasma concentration ratio 45-150), whereas the excretion of TB was significantly lower than its metabolites (urinary-to-plasma concentration ratio 4-6). N3-demethylation of TB accounted for 58 +/- 7% of the urinary metabolites, N7-demethylation for 27 +/- 6%, C8-oxidation of 7-X for 22 +/- 4%, C8-oxidation of 3-X for 2 +/- 2% and formation of 6-AMMU for 13 +/- 4%. The ratio of N3- to N7-demethylation of TB remained constant during the load, but the large interindividual variation observed in ratio makes it unsuitable as a function test for evaluation of liver disease.

Evaluation of the developmental toxicity of theophylline, dimethyluric acid, and methylxanthine metabolites using Xenopus.

The developmental toxicities of theophylline and theophylline metabolites were evaluated using FETAX (Frog Embryo Teratogenesis Assay - Xenopus). Young X. laevis embryos were exposed to theophylline, 1-methylxanthine, 3-methylxanthine, or 1, 3-dimethyluric acid in each of two separate concentration-response experiments with and without an exogenous metabolic activation system (MAS) and/or inhibited MAS. The MAS was treated with carbon monoxide (CO), cimetidine (CIM), or ellipticine (ELL) to selectively modulate cytochrome P-450 activity. Addition of the MAS and CIM-MAS reduced the developmental toxicity of theophylline. Addition of the ELL- or CO-inhibited MAS did not reduce the developmental toxicity of theophylline. Addition of the intact MAS did not alter the developmental toxicity of 1-methyl- or 3-methylxanthine which were slightly more developmentally toxic on an equimolar basis than theophylline itself. 1, 3-dimethyluric acid was not developmentally toxic at maximum soluble concentrations in 1% (V/V) DMSO. Results from these studies suggested that P-450, specifically ELL-inhibited P-450 (aryl hydrocarbon hydroxylase) may have been responsible for detoxification of theophylline and that 1, 3 dimethyluric acid represented the primary detoxification metabolite of theophylline.

ChemInform Abstract: Comparison of Electrochemical and Enzymatic Oxidation of 3,9‐ Dimethyluric Acid.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Effect of Q-35, New Pyridone Carboxylic Acid, on Theophylline Metabolism in Rat Liver Microsomes.

Q-35, (±)-1-Cyclopropyl-6-fluoro-1, 4-dihydro-8-methoxy-7-(3-methylaminopiperidine-1-yl)-4-oxoquinoline-3-carboxylic acid, is a new pyridone carboxylic acid antibiotic(NQ). Certain NQs have been reported to inhibit theophylline (TP) metabolism in vivo and in vitro. We investigated the effect of Q-35 on TP metabolism by rat liver microsomes. TP was incubated with rat liver microsomes in the presence of Q-35, enoxacin, ofloxacin or ciprofloxacin. The effect of NQ was evaluated in terms of the formation of main TP metabolite, 1, 3-dimethyluric acid. Enoxacin strongly inhibited this formation while Q-35 showed the lowest inhibitory effect among four NQs. Relationship between the structure and inhibitory effect of the Q-35 derivatives was studied. 3'-amino substituents in 7-pyperidinyl group showed a strong inhibitory activity, while the 3'-methylamino and 4'-amino substituents were weak inhibitors. Little enantiomeric effect was observed at the 3'-position. The methoxy group in the 8-position reduced inhibitory effect. From these results, the Q-35 has little effect on TP metabolism and the effects of Q-35 derivatives on TP metabolism depends on the stereochemical stsucture of 7- and 8- substituents.

The Pharmacokinetics of Theophylline and Its Major Metabolites in Cystic Fibrosis

The pharmacokinetics of theophylline and its metabolites were studied in 13 patients with cystic fibrosis (CF) after an intravenous bolus of aminophylline (6 mg/kg) followed by multiple dosing with sustained release theophylline (Theo-Dur®) (7.7-14.8 mg/kg/day). An agematched group of 18 healthy subjects, taking a single oral dose of theophylline (300 mg), was used as a control group for comparing theophyline pharmacokinetic parameters. Literature values were used for the pharmacokinetics of the theophylline metabolites in normal subjects. Serum and urine concentrations of theophylline and its three main metabolites [3 methylxanthine (3MX), 1 methyluric acid (1MU), and 1,3 dimethyluric acid (1,3DMU)] were assayed by HPLC. The total body clearance and volume of distribution were significantly greater (p<0.01) in patients with CF than in control subjects. The steady-state serum concentration of 1 MU was greater in patients with CF than previously reported in normals. CF patients also had a lower plasma protein binding of theophylline. The symptomatic intolerance of theophylline in patients with CF may be related to an accumulation of this metabolite or a greater free fraction of theophylline or both.

Isolation and characterization of 5-[3'-(7',9'-dimethyluric acid)]-7,9-dimethyl-Δ 3,4-isouric acid : An unstable product of electrochemical oxidation of 7,9-dimethyluric acid

Isolation and characterization of 5-[3'-(7',9'-dimethyluric acid)]-7,9-dimethyl-Δ 3,4-isouric acid : An unstable product of electrochemical oxidation of 7,9-dimethyluric acid

Lack of effect of terfenadine on theophylline pharmacokinetics and metabolism in normal subjects.

The pharmacokinetics of oral theophylline (250 mg) and the production of its metabolites (3-methylxanthine, 1-methyluric acid, 1,3-dimethyluric acid) were studied before and after the administration of oral terfenadine (120 mg twice daily for 16 days) in 10 healthy volunteers. Comparison of volumes of distribution, elimination half-lives, areas under the plasma concentration-time curves, plasma clearance of theophylline and elimination of theophylline metabolites indicated that terfenadine had no significant effect on theophylline pharmacokinetics and metabolism.

MEASUREMENT OF URINARY METABOLITES OF THEOPHYLLINE AND SERUM THEOPHYLLINE LEVEL WITH ASTHMATIC CHILDREN

The examination of urinary theophylline and theophylline metabolism were studied in 7 asthmatic children. High-pressure liquid chromatography was devised to quantitate theophylline metabolites in the 24-hr urine of 5 patients and in the time course of 2 patients who had been receiving 20mg/kg of theophylline orally in a day. Mean values for the theophylline-derived urine products were unchanged theophylline 15.3±4.07, 3-methylxanthine 14.0±1.86, 1, 3-dimethyluric acid 38.9±6.62, and 1-methyluric acid 31.8±6.65 (%). Metabolites were exprssed as internal standard equivalents on a molar basis. There was a direct correlation between urinary 3-methylxanthine and 1-methyluric acid and a inverse correlation between 1, 3-dimethyluric acid and 1-methyluric acid+3-methylxanthine, 1, 3-dimethyluric acid and 1-methyluric acid, unchanged theophylline and 1-methyluric acid+1, 3-dimethyluric acid, unchanged theophylline and 3-methylxanthine in urine, respectively. In the case of 2 patients in time course measurerent, the urine content of theophylline and 1-methyluric acid+1, 3-dimethyluric acid were inversely related. The urinary unchanged theophylline and 3-methylxanthine were also inversely related. There were some relations between the concentration of urinary unchanged theophylline and those of serum theophylline. This might reflect the capacity in theophylline metabolism because it was different among patients. From this we suggest it would be useful to determine the most appropriate administration of theophylline.

血清中テオフィリン濃度測定におけるＰａｒｔｉｃｌｅ‐Ｅｎｈａｎｃｅｄ Ｔｕｒｂｉｄｉｍｅｔｒｉｃ Ｉｎｈｉｂｉｔｉｏｎ Ｉｍｍｕｎｏａｓｓａｙの評価

We evaluated the particle-enhanced turbidimetric inhibition immunoassay (PETINIA) for the measurement of theophylline in serum. The coefficients of variation in both within-day (n= 10) and between-day (n=10) precision studies were less than 4 %, and the analytical recoveries were 98-103% at the concentrations of 5, 10 and 20μg/ml of theophylline. Good correlations were observed among assay results by PETINIA, high-performance liquid chromatography (HPLC) and fluorescence polarization immunoassay (FPIA) for 120 serum specimens cbllected from patients with chronic obstructive pulmonary disease receiving theophylline therapy.The regression lines obtained were: PETINIA =1.034 x HPLC -0.404 (r =0.994, Sy/x=0. 57μg/ ml), PETINIA =1.037 x FPIA-0.539 (r=0.995, Sy/x=0.51μg/ml). The cross reactivity in PETINIA was also studied with 11 compounds structurally related to theophylline. None of these compounds exhibited significant cross reactivity (less than 5 %) except for 1, 3-dimethyluric acid (11%). From these results, we could conclude that PETINIA is a useful method for therapeutic monitoring of serum theophylline having good precision and accuracy, and high specificity.

血清中テオフィリン濃度測定のためのセラライザー法の評価

Seralyzer system applying apoenzyme reactivation immunoassay system for determination of serum theophylline concentration (SERALYZER method) was evaluated. The coefficients of variation of within-run and between-run precisions for 3 concentrations of theophylline in serum were less than 4%. The serum theophylline concentrations determined by SERALYZER method for 40 samples were compared with those determined by high-performance liquid chromatography (HPLC), substrate-labeled fluorescent immunoassay method-fluorostat (SLFIA method-A), SLFIA method-OPTIMATE (SLFIA method-B) and fluorescence polarization immunoassay method (FPIA method). There were good agreements between HPLC and SERALYZER method results, SLFIA method-A and SERALYZER method results, SLFIA method-B and SERALYZER method results, and FPIA method and SERALYZER method results, where all correlation coefficients were 0.996. The cross-reactivities of caffeine, 8-chlorotheophylline, 1, 3-dimethyluric acid, 1, 7-dimethylxanthine, 3-methylxanthine, theobromine, and 1, 3, 7-trimethyluric acid in SERALYZER method were found. However, these cross-reactivities are not serious problems in clinical condition. Therefore, the SERALYZER method may be useful for the drug-level monitoring of patients under theophylline therapy.