Visualization of AMPA receptors in living human brain with positron emission tomography.

Although aberrations in the number and function of glutamate AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors are thought to underlie neuropsychiatric disorders, no methods are currently available for visualizing AMPA receptors in the living human brain. Here we developed a positron emission tomography (PET) tracer for AMPA receptors. A derivative of 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyacetamide radiolabeled with 11C ([11C]K-2) showed specific binding to AMPA receptors. Our clinical trial with healthy human participants confirmed reversible binding of [11C]K-2 in the brain according to Logan graphical analysis (UMIN000020975; study design: non-randomized, single arm; primary outcome: dynamics and distribution volumes of [11C]K-2 in the brain; secondary outcome: adverse events of [11C]K-2 during the 4-10 d following dosing; this trial met prespecified endpoints). In an exploratory clinical study including patients with epilepsy, we detected increased [11C]K-2 uptake in the epileptogenic focus of patients with mesial temporal lobe epilepsy, which was closely correlated with the local AMPA receptor protein distribution in surgical specimens from the same individuals (UMIN000025090; study design: non-randomized, single arm; primary outcome: correlation between [11C]K-2 uptake measured with PET before surgery and AMPA receptor protein density examined by biochemical study after surgery; secondary outcome: adverse events during the 7 d following PET scan; this trial met prespecified endpoints). Thus, [11C]K-2 is a potent PET tracer for AMPA receptors, potentially providing a tool to examine the involvement of AMPA receptors in neuropsychiatric disorders.

Development of a LC-MS/MS method for the estimation of clinofibrate in human urine.

A highly sensitive and rapid liquid chromatography-tandem mass spectrometry method was developed for the determination of clinofibrate in human urine. The analyte and IS were extracted through a simple protein precipitation by the mixture of acetonitrile and 1 mol/L hydrochloric acid (95:5, v/v) and separated on an Inspire C18 (150 mm x 4.6 mm I.D., 5 µm particle size) column using isocratic elution with methanol and water containing 0.1% formic acid and 10 mM ammonium acetate (90:10, v/v). Mass spectrometric detection was performed in electrospray positive ionization MRM mode. The mass transition was m/z 486.3-->175.0 for clinofibrate and m/z 361.1-->233.1 for IS, respectively. The flow rate was 0.6 mL/min and the column oven temperature was set at 35 °C. The total run time was 6.5 min. Good linear relationships were obtained for all analytes over the concentrations ranging of 0.1002-10.02 µg/mL (r2 = 0.9991) and the limit of quantification was 0.1002 µg/mL. The extraction recovery was larger than 87.4% and intra- and inter-batch precision and accuracy with RSD were all less than 6.5%. The total amount of unchanged clinofibrate excreted in urine was less than 0.34%. This method was successfully applied to the pharmacokinetic study of clinofibrate in human urine.

Characterization of in vitro biotransformation of the new oral anticoagulants, the factor VIIa inhibitors AS1927819-00 and AS1932804-00.

We recently developed a prodrug (AS1932804-00, CMP) of the novel FVIIa inhibitor AS1924269-00, which possesses a carbamate amidine backbone. In addition, we developed another type of prodrug (AS1927819-00, OXP) with an oxime amidine backbone. In this study, we investigated the efficiency of conversion of these novel FVIIa prodrugs to their active forms by evaluating the production of the active form in vitro by using microsomes, mitochondria, and cryopreserved hepatocytes, and compared it with the in vivo conversion mechanisms of the prodrugs (oxime amidine vs. carbamate amidine). We observed that OXP and CMP showed improved oral absorption, and the efficiency of conversion of CMP to the active form was higher than that of OXP. The in vivo rate of conversion of OXP to its active form was low in rats, and compared to liver microsomes and mitochondria, cryopreserved hepatocytes supplemented with serum and coenzymes were an appropriate metabolic test tool. On the other hand, the efficiency of conversion of CMP to its active from could be appropriately evaluated using small intestinal microsomes. The development of a prodrug can be optimized when information about the stability of carboxylic acid esters in the presence of serum esterases, membrane permeability of intermediate forms, and differential tissue specificity to metabolic activities for carbamate and oxime backbones of amidine can be obtained.

Effect of food on the single-dose pharmacokinetics and tolerability of clinofibrate tablets in Chinese healthy volunteers.

The aim of this study is to investigate a food effect on the single-dose pharmacokinetics and tolerability of clinofibrate tablets in 12 Chinese healthy volunteers. The authors evaluated the effect of being under a fasting or fed state at the time of drug intake on the single-dose of clinofibrate 400 mg tablets in a randomized, balanced, single-dose, two-treatment (fed and fasting), two-period, two-sequence study design with a 7-day washout period. The end points were the maximum plasma drug concentration (Cmax) and areas under the plasma-concentration curve (AUC) for 72 hours exposure (AUC0-72) and total exposure (AUC0-∞). All participants completed the whole study without side effects being observed. The Cmax mean of clinofibrate glucuronides and parent clinofibrate were 21.91, 17.85 µ/ml for the fasting state and 13.14, 11.25 µ/ml for the fed state, respectively. The AUC0-72 and AUC0-∞ of clinofibrate glucuronides and parent clinofibrate were 381.60, 307.07 µ/ ml and 404.55, 342.24 µ/ml for the fasting state and 379.02, 321.14 µ/ml and 432.24, 351.80 µ/ml for the fed state. The authors showed that food intake was associated with a significant decrease in Cmax, but no significant change in AUC values.

Pharmacokinetics of the amidine prodrug of a novel oral anticoagulant factor VIIa inhibitor (AS1924269-00) in rats.

AS1924269-00 is a promising orally applicable anticoagulant that inhibits FVIIa but has very low oral absorption. Therefore, in this study, we aimed to develop a prodrug of AS1924269-00, which possesses a carbamate-added amidine functional group, with high membrane permeability. We investigated the pharmacokinetics of the carbamate-type prodrug of AS1924269-00 in rats. The Caco-2 cell monolayer was used as an in vitro model and in parallel an artificial membrane permeability assay (PAMPA) was performed to examine the transport mechanisms of the prodrug. The bioavailability of the active form was determined to be only 0.3% in rats, but the oral absorption of the prodrug was markedly improved, and its bioavailability was 36%. Our in vivo result was consistent with the finding that compared to AS1924269-00, the prodrug showed favorable permeability in Caco-2 cells and PAMPA. We introduced carbamate into the amidine functional group of the FVIIa inhibitor, which possesses the amidine backbone, and converted it to a prodrug using carboxylic acid ethyl ester. This novel prodrug had favorable absorption and membrane permeability in vivo and in vitro. Thus, we suggest a clinical application of the carbamate-added amidine prodrug of the FVIIa inhibitor.

High-performance liquid chromatographic method for determination of clinofibrate and its application to a pharmacokinetic study in healthy volunteers.

A convenient and rapid HPLC method was developed for the determination of clinofibrate in human plasma using simple protein precipitation with the mixture of acetonitrile and 1M hydrochloric acid (95:5, v/v) followed by separation using an Inspire C(18) column with isocratic elution. The detection wavelength was 232nm and the flow rate was 1.0ml/min. The mobile phase consisted of acetonitrile and water containing 0.4% ortho-phosphoric acid (73:27, v/v). Linear calibration curve was obtained over the concentrations ranging from 0.5µg/ml to 32µg/ml (r(2)=0.999) with LLOQ of 0.5µg/ml. The RSD in both the intra-run and inter-run precision study was less than 5.4% and the extraction recoveries were above 90.7%. The HPLC method is reproducible and suitable for the quantification of clinofibrate in plasma. This method was successfully applied to the pharmacokinetic studies of clinofibrate in healthy volunteers. The elimination half-lives (t(1/2)) were (20.47±3.44), (18.19±2.62) and (21.51±4.78)h after single oral administration of 200, 400 and 600mg clinofibrate, respectively. The results of WinNonlin software showed that the area under the plasma concentration versus time curve from time 0 to 72h (AUC(0-72)) and peak plasma concentration (C(max)) were linearly related to dose (P>0.05).

Uptake of phenoxyacetic acid by Penicillium chrysogenum.

The uptake of phenoxyacetic acid by two different strains of Penicillium chrysogenum was studied. Phenoxyacetic acid (POA) was taken up by P. chrysogenum in a defined medium. Plots of initial velocity of POA uptake versus external substrate concentration, in the range 2-5000 microM, gave linear plots. Uptake of POA by induced and uninduced cells was identical. The initial velocity of POA uptake decreased as the pH of the suspension was increased from 5.4 to 7.2; the decrease closely paralleled the decline in the non-ionic form of the acid over this pH range. The initial velocity of POA uptake was not affected by the presence of phenylacetic acid. POA uptake proceeded until the cellular concentration was equal to the external concentration. It is concluded that POA is passively transported into P. chrysogenum by unmediated diffusion.

Hypertriglyceridemia and lowered apolipoprotein C-II/C-III ratio in uremia: effect of a fibric acid, clinofibrate.

We examined the effects of a fibric acid, clinofibrate, on lipoprotein metabolism in 12 hyperlipidemic patients with uremia treated on continuous ambulatory peritoneal dialysis during a 24 week treatment. Daily dose of clinofibrate was 200 mg for the initial four weeks, 400 mg for the second four weeks, and 600 mg for the subsequent 16 weeks. Serum and very-low density lipoprotein (VLDL) triglyceride were decreased by 36% and 48%, respectively. Neither total cholesterol nor apolipoprotein B changed significantly, whereas cholesterol was decreased in VLDL and increased in low (LDL) and high density lipoprotein (HDL) fractions. Post-heparin plasma lipoprotein lipase (LPL) before treatment was not lower than the normal value, and we found no change in LPL activity following clinofibrate. Hepatic triglyceride lipase also did not change. Apolipoprotein (apo) C-II/C-III ratio was low as compared to the normal value before treatment, and the ratio was increased by 38% after the treatment. Decrease in VLDL triglyceride was associated with increase in apo C-II/C-III ratio in all the cases. Abnormal enrichment with triglyceride of LDL and HDL fractions was improved by clinofibrate. Although one patient had a transient and asymptomatic elevation of serum creatine phosphokinase, no patient had muscle pain. There was no accumulation of the drug in the 24 week trial. These results suggest that clinofibrate is an effective and safe approach to the management of dyslipidemia in CAPD patients.

Radioiodinated phenoxyacetic acid derivatives as potential brain imaging agents. II. Structure-biodistribution relationship.

In developing new brain imaging agents for single photon emission computed tomography (SPECT), we synthesized eleven radioiodinated phenoxyacetic acid derivatives and investigated the relationship between the chemical structure and in vivo characteristics. Biodistribution studies in mice revealed high initial brain uptake for all the compounds. Blood radioactivity level depended markedly upon the chemical stability of the compound. The alpha, alpha-dimethylester derivative (1e), amide derivatives (2a--c) and diamine derivatives (3a, b, 4), which were stable to hydrolysis, showed low blood activity levels following i.v. administration. Disappearance of the ester and amide compounds from the brain was rapid. However, the diamine derivatives displayed improved retention in the brain. Compounds 3a and 4 possessed the best combination of high brain uptake and sufficient retention to be useful as potential brain imaging radiopharmaceuticals with SPECT devices.

Contraluminal organic anion and cation transport in the proximal renal tubule: V. Interaction with sulfamoyl- and phenoxy diuretics, and with beta-lactam antibiotics.

In order to study the interaction of sulfamoyl- and phenoxy diuretics as well as of beta-lactam antibiotics with the contraluminal anion and cation transport systems the inhibitory potency of these substances against the influx of 3H-para-aminohippurate, 14C-succinate, 35S-sulfate and 3H-N1-methylnicotinamide into cortical tubular cells have been determined. 1.) 2-, 3- and 4-sulfamoylbenzoate inhibit contraluminal PAH influx. N-dipropyl substitution to yield probenecid or ring-substitution to yield furosemide and piretanide augment the inhibitory potency. However, hydrochlorothiazide and acetazolamide exert only a moderate inhibitory potency. Succinate transport was inhibited by furosemide only. Sulfate transport was inhibited by furosemide and 3-sulfamoyl-4-phenoxybenzoate as well as by probenecid, piretanide, hydrochlorothiazide and acetazolamide. 2.) Phenoxyacetate, -propionate, and -butyrate exert increasing inhibition against PAH transport. The weed-killers 2,4-dichloro-, and 2,4,5-trichlorophenoxyacetate (2,4 D and 2,4,5 T) had a similar inhibitory potency, while ethacrynic acid showed a lower and the uricosuric tienilic acid a higher inhibitory potency. None of the compounds of this group interact with contraluminal succinate transport, and only the multiring-substituted compounds 2,4 D, 2,4,5 T, ethacrynic and tienilic acid interact slightly with the sulfate transporter. 3.) The monocarboxylic penicillins benzylpenicillin and phenoxymethylpenicillin as well as the dicarboxylic ticarcillin interact with the contraluminal PAH transport. The aminopenicillin ampicillin had a lower, and apalcillin a higher inhibitory potency than monocarboxylic penicillin. Benzylpenicillin showed small inhibition against succinate transport and ticarcillin against sulfate transport. 4.) The monocarboxylic cephalosporine, 6315 S Shionogi, and the aminocephalosporines, cephalexin and cefadroxil, showed an app. Ki.PAH as the comparable penicillins. The zwitterions cephaloridine and cefpirome did not interact with the PAH transporter, but with the organic cation (NMN) transporter. Amongst the amino-thiazol-containing compounds cefotaxime, ceftriaxone, and cefodizime, increasing interaction with the PAH transporter was seen dependent of a second ionizable anionic group. Compounds with two ionizable anionic groups (cefsulodin, ceftriaxone, cefodizime) exert also a small inhibitory potency against sulfate transport. None of the cephalosporins interacted with the dicarboxylate transporter. The interaction pattern of the tested compounds is in accordance with the specificity requirements for the contraluminal transporters depending on electrical charge and hydrophobicity.

Activity of agricultural chemicals to modify mitomycin C induced growth inhibition of Bacillus subtilis in the rec assay.

Rec assay of agricultural chemicals, MCPA-E, MCPA, CNP and PCNB was conducted. It was found that MCPA-E and MCPA accelerated the growth-inhibition originally induced by Mitomycin C in the rec- strain.

Diuretics physiology pharmacology and clinical use

Uricosuric diuretics have been developed to counteract renal urate retention accompanying diuretic-induced extracellular volume contraction. Their intrinsic uricosuric activity would prevent diuretic-induced hyperuricemia. Ticrynafen, a prototype uricosuric diuretic, has largely fallen into disuse because of hepatic toxicity. However, one lesson learned during the short period that ticrynafen was available in the US is that the administration of a potent uricosuric agent to a patient previously trated with diuretics can precipitate acute renal failure, possibly as a consequence of uric acid nephropathy. Another novel uricosuric diuretic, indacrinone, is composed of two enantiomorphic isomers exhibiting predominantly either a uricosuric or a natriuretic action. Manipulation of the isomer ratio currently is being attempted with a view toward obtaining a combination that produces little change in the serum urate during chronic diuretic therapy. Uricosuric diuretics have the therapeutic potential to treat hypertension and edematous states without increasing the serum urate. Although current information suggests that chronic asymptomatic hyperuricemia poses very little health hazard, future data could indicate that it may be desirable to maintain the serum urate near the normal range