Effect of acute hepatic failure on the hepatic first‐pass effect of 5‐fluorouracil in rats

Objectives In cancer chemotherapy for hepatocellular carcinoma, 5‐fluorouracil is widely used and has typically been given by intrahepatic arterial (i.a.) infusion to increase treatment efficacy and reduce systemic toxicity. 5‐Fluorouracil is eliminated primarily by the liver and so the hepatic first‐pass effect after intrahepatic arterial administration of 5‐fluorouracil may be lower in patients with hepatic failure, and systemic toxicity may not be reduced. In this study, we have investigated the effect of acute hepatic failure on the first‐pass effect of 5‐fluorouracil in rats. Methods Experimental acute hepatic failure was induced by treatment with carbon tetrachloride (CCl₄). 5‐Fluorouracil was infused for 15 min into the hepatic artery or the saphenous vein of rats at a dose of 1.25 mg/kg. Key findings Hepatic availability in 50% CCl₄‐treated (severe hepatic failure) rats was higher than in controls. Conclusions The hepatic first‐pass effect after intrahepatic arterial administration of 5‐fluorouracil was lower in severe hepatic failure. Therefore, the reducing effect of the systemic toxicity after intrahepatic arterial administration may be lower in severe hepatic failure.     

Synthesis and purification of [2‐13C]‐5‐fluorouracil

[2‐¹³C]‐5‐Fluoropyrimidine‐2,4(1H,3H)‐dione ([2‐¹³C]‐5‐fluorouracil or [2‐¹³C]‐5‐FU) is a potential diagnostic agent for measuring 5‐FU‐induced toxicity in cancer patients. It was prepared and purified with isotopic and chemical purity of>99% on a multigram scale in a two‐step synthesis from [¹³C]‐urea. Preparative separation of [2‐¹³C]‐FU and [2‐¹³C]‐uracil was carried out by automated medium pressure silica gel column chromatography. The method is applicable to a broader range of 5‐FU isotopic analogs derived from labeled uracil. Copyright © 2011 John Wiley & Sons, Ltd.     

Mechanisms responsible for the altered pharmacokinetics of Bosentan: analysis utilizing rats with bile duct ligation‐induced liver dysfunction

The purpose of this study was to evaluate the mechanisms responsible for the pharmacokinetic variability of bosentan utilizing rats with liver dysfunction induced by 7‐day bile duct ligation (BDL). Bosentan was administered intravenously at a constant infusion rate (I) of 24, 40 or 60 µg/min/kg. The blood bosentan concentration (BBC) following infusion was measured by HPLC, and apparent clearance (CL) of the drug was estimated as I/BBC. The CL values in normal rats were 30.5 and 19.3 ml/min/kg at infusion rates of 24 and 60 µg/min/kg, respectively, suggesting non‐linear pharmacokinetics of bosentan. The BBC in BDL rats was much higher than that in normal rats, and the CL values in BDL rats were 3.80 and 3.08 ml/min/kg at infusion rates of 24 and 60 µg/min/kg, respectively. The CL value of bosentan at an infusion rate of 40 µg/min/kg in normal rats was decreased significantly by the coadministration of taurocholic acid or bilirubin. In addition, the hepatic mRNA expression of CYP2C6, CYP3A2, Oatp1a1, Oatp1a4 and Oatp1b2 in BDL rats decreased to 77.6%, 34.0%, 65.4%, 84.8% and 44.2% of that in normal rats, respectively. These results suggested that bile acids and/or bilirubin accumulated in BDL rat plasma inhibited the hepatic uptake of bosentan, and that the decreased bosentan clearance in BDL rats was caused at least partly by the impaired expression of hepatic drug‐metabolizing enzymes and uptake transporters. Moreover, because the pharmacokinetics of bosentan was non‐linear at the tested doses, the increased BBC in BDL rats might further induce the saturation of hepatic uptake and/or metabolism of bosentan. Copyright © 2009 John Wiley & Sons, Ltd.     

Influence of vasomodulators and tumor transplantation on the disposition of 5‐fluorouracil after application to the liver surface in rats

This study investigated the effect of epinephrine (a vasoconstrictor) and hydralazine (a vasodilator) on the hepatic disposition of 5‐fluorouracil (5‐FU) after application to the surface of the liver in rats. Normal livers were compared with a Walker 256 carcinoma cell tumor model. A cylindrical diffusion cell was attached to the liver surface. 5‐Fluorouracil was added into the diffusion cell in combination with vasomodulators or after pretreatment with epinephrine. After selected treatment times, the 5‐FU concentrations were assayed at three sites in the excised livers. The 5‐FU concentration in the region under the cell attachment site (site 1) was significantly higher after concomitant application of 5‐FU and epinephrine, compared with 5‐FU alone, and increased in an epinephrine dose‐dependent manner. On the other hand, preferential distribution of 5‐FU at site 1 was not seen when applied in combination with hydralazine. After 10 min of epinephrine pretreatment, the concentration of 5‐FU at site 1 was approximately two times higher than that for the control. Furthermore, the 5‐FU concentration at site 1 of the tumor model was greatly increased compared with the normal liver. These results suggest that application of epinephrine to the liver surface might enhance the accumulation of 5‐FU at the desired target site.     

A predictive biomarker for altered 5‐fluorouracil pharmacokinetics following repeated administration in a rat model of colorectal cancer

The relationship between the plasma ratio of dihydrouracil/uracil (UH2/Ura) and hepatic dihydropyrimidine dehydrogenase (DPD) activity after repeated 5‐fluorouracil (5‐FU) treatment in rats with colorectal cancer (CRC) was investigated. Repeated intravenous 5‐FU bolus injections resulted in a significant decrease in the total clearance (CL_tot) and an increased area under the curve (AUC_0‐∞) in CRC rats. Furthermore, the hepatic DPD levels and the plasma ratio of UH2/Ura decreased significantly and lost their circadian rhythms in CRC rats treated repeatedly with 5‐FU, although significant circadian variation in the two parameters was observed in the control CRC rats. Moreover, a significant correlation was found between the plasma ratio of UH2/Ura and hepatic DPD activity in CRC rats untreated and treated with single or repeated 5‐FU administration (r² = 0.865, p < 0.01). The ratio of UH2/Ura in plasma could be a predictive biomarker of the suppression of hepatic DPD levels during repeated 5‐FU‐based treatment. Furthermore, by plotting the observed pharmacokinetic parameters of 5‐FU against hepatic DPD activity levels predicted by the ratio of UH2/Ura in plasma, AUC_0‐∞, CL_tot and half‐life (t_1/2) were closely linked to predicted hepatic DPD activity levels. These observations suggest that the factor that significantly influences the AUC_0‐∞, CL_tot and t_1/2 of 5‐FU after single or repeated administration of 5‐FU is the hepatic DPD activity and it could be assessed by the ratio of UH2/Ura in plasma. Copyright © 2013 John Wiley & Sons, Ltd.     

Time‐dependent effects of Klebsiella pneumoniae endotoxin on the pharmacokinetics of chlorzoxazone and its main metabolite, 6‐hydroxychlorzoxazone,in rats: restoration of the parameters in 96 hour in KPLPS rats to control levels

It has been reported that chlorzoxazone (CZX) was primarily metabolized via hepatic Cyp2e1 to form 6‐hydroxychlorzoxazone (OH‐CZX) in rats, and the activity of aniline hydroxylase (a Cyp2e1 marker) in the liver was significantly decreased in rats at 24 h after pretreatment with lipopolysaccharide derived from Klebsiella pneumoniae (24 h KPLPS rats), whereas the levels were not changed at 2 h and 96 h in the KPLPS rats. Thus, the time‐dependent pharmacokinetic parameters of CZX and OH‐CZX were evaluated after the intravenous administration of CZX (20 mg/kg) to control rats, and the 2 h, 24 h and 96 h KPLPS rats along with the time‐dependent changes in the protein expression of hepatic Cyp2e1. After the intravenous administration of CZX to 24 h KPLPS rats, the AUC_{0–2 h} of OH‐CZX and AUC_{OH‐CZX, 0–2 h}/AUC_CZX were significantly smaller (by 40.5% and 71.2%, respectively) than those of controls due to the significant decrease (by 75.3%) in the protein expression of hepatic Cyp2e1. However, in 96 h KPLPS rats, the pharmacokinetic parameters of both CZX and OH‐CZX were unchanged compared with controls due to the restoration of the protein expression of hepatic Cyp2e1 to control levels. These observations highlighted the existence of the time‐dependent effects of KPLPS on the pharmacokinetics of CZX and OH‐CZX in rats. Copyright © 2009 John Wiley & Sons, Ltd.     

Application of an LC‐MS/MS method to the pharmacokinetics of TM‐2, a potential antitumour agent,in rats

TM‐2 is a novel semi‐synthetic taxane derivative, selected for preclinical development based on its greater anticancer activity and lower toxicity compared with docetaxel. In this study, a rapid and sensitive analytical method based on ultra performance liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) has been developed for the determination of TM‐2 in rat plasma. The biological samples were extracted with methyl tert‐butyl ether and separated on a C₁₈ column (50 mm × 2.1 mm, 1.7 µm) using a mobile phase consisting of acetonitrile and 2 mM ammonium acetate. The standard curves were linear over the range 5–1000 ng/mL in rat plasma. The precision (relative standard deviation, RSD, %) were within 14.5%, and the accuracy (relative error, RE, %) ranged from ?1.56 to 2.36%. Recovery and matrix effect were satisfactory in rat plasma. The validated method was successfully applied to pharmacokinetic studies after intravenous administration of TM‐2 to rats. The pharmacokinetics of TM‐2 in rats were characterized by a large volume of distribution and a long half‐life of elimination after single dose (4, 8, and 16 mg/kg), and a good correlation was observed between AUC and dose. The preclinical data will be useful for the design of subsequent trials of TM‐2. Copyright © 2014 John Wiley & Sons, Ltd.     

5‐Fluorouracil treatment alters the expression of intestinal transporters in rats

5‐Fluorouracil (5‐FU), an anticancer drug, causes severe gastrointestinal damage, which may affect the absorption of orally administered drugs including the substrates of intestinal uptake and efflux transporters. This study aimed to investigate quantitatively the effect of 5‐FU‐induced intestinal damage on the expression of intestinal transporters: P‐glycoprotein (P‐gp), breast cancer resistance protein (BCRP) and peptide transporter 1 (PEPT1) in rats. The rats were treated with 5‐FU (30 mg/kg/day, p.o. ) for 5 days to induce intestinal damage, and then the upper, middle and lower intestinal segments were removed. The mRNA and protein expression levels of these transporters in each segment were determined using quantitative real‐time PCR and Western blotting, respectively. In the 5‐FU‐treated rats, the protein levels of P‐gp and Bcrp in the upper segment were significantly increased to 15‐ and 2.6‐fold of the control, respectively, while those in other segments were unaffected. Pept1 expression was increased by 5‐FU in almost all segments. A remarkable increase in P‐gp expression was shown, the uptake of digoxin, a P‐gp substrate, in each intestinal segment was measured using a rat everted sac. As a result, the uptake of digoxin in the upper segments of 5‐FU‐treated rats was decreased compared with that of the control. In conclusion, 5‐FU‐induced intestinal damage was shown to alter the expression of these transporters, especially in the upper intestinal segment, while the characteristics of the influence varied among the transporters. The 5‐FU‐induced intestinal damage may affect transporter‐mediated drug absorption of orally administered drugs in the clinical setting.     

Effect of moderate or severe liver dysfunction on the pharmacokinetics of γ-hydroxybutyric acid

Objectives: To assess the effect of moderate or severe liver dysfunction on the pharmacokinetics of γ-hydroxybutyric acid (GHB). Methods: The absorption and disposition kinetics of GHB were studied in eight cirrhotic patients without ascites (Child’s class A) and eight cirrhotic patients with ascites (Child’s class C), after administration of a single oral dose of 25 mg⋅kg⁻¹. The liver metabolic function of each patient was evaluated by measuring antipyrine clearance and the formation rate of the lidocaine metabolite monoethylglycinexylidide (MEGX). Results: Compared to those previously determined in eight healthy control subjects given the same GHB dose, mean AUC values were double or greater in the cirrhotic patients. Accordingly, apparent oral clearance was markedly reduced (from 9.1 to 4.5 and 4.1 ml⋅min⁻¹⋅kg⁻¹ in nonascitic and ascitic patients, respectively). Terminal half-life (t_1/2), was significantly longer in nonascitic patients than in control subjects (32 vs 22 min). A further significant prolongation of t_1/2, most likely due to an increased distribution volume, was observed in patients with ascites (56 min). Nonetheless, GHB plasma concentrations fell to either undetectable or negligible levels by the end of the usual dosing intervals (6–8 h). More limited changes were noted in the absorption parameters. The peak level (C_max) increased only in nonascitic patients, but not proportionally to the increase in AUC. The time to C_max increased from 30 to 45 min in both cirrhotic groups. These findings are consistent with a slowed rate of GHB absorption in cirrhotic patients. Adverse effects were similar, for intensity and duration, to those recorded in healthy volunteers, i.e., mild and transient. Conclusions: Although liver cirrhosis causes significant modifications of GHB disposition kinetics, the increase in t_1/2 is not such as to cause drug accumulation on repetitive dosing. However, in consideration of the higher mean plasma levels observed in cirrhotic patients, it appears wise to keep the initial GHB daily dose at the lower end of the therapeutic range and to carefully monitor the patients if upward dose adjustments are required. Received: 27 July 1995/Accepted in revised form: 24 November 1995     

Combinational treatment of 5‐fluorouracil and casticin induces apoptosis in mouse leukemia WEHI‐3 cells in vitro

Leukemia is one of the major diseases causing cancer‐related deaths in the young population, and its cure rate is unsatisfying with side effects on patients. Fluorouracil (5‐FU) is currently used as an anticancer drug for leukemia patients. Casticin, a natural polymethoxyflavone, exerts anticancer activity against many human cancer cell lines in vitro, but no other reports show 5‐FU combined with casticin increased the mouse leukemia cell apoptosis in vitro. Herein, the antileukemia activity of 5‐FU combined with casticin in WEHI‐3 mouse leukemia cells was investigated in vitro. Treatment of two‐drug combination had a higher decrease in cell viability and a higher increase in apoptotic cell death, the level of DNA condensation, and the length of comet tail than that of 5‐FU or casticin treatment alone in WEHI‐3 cells. In addition, the two‐drug combination has a greater production rate of reactive oxygen species but a lower level of Ca²⁺ release and mitochondrial membrane potential (ΔΨ_m) than that of 5‐FU alone. Combined drugs also induced higher caspase‐3 and caspase‐8 activities than that of casticin alone and higher caspase‐9 activity than that of 5‐FU or casticin alone at 48 hours treatment. Furthermore, 5‐FU combined with casticin has a higher expression of Cu/Zn superoxide dismutase (SOD [Cu/Zn]) and lower catalase than that of 5‐FU or casticin treatment alone. The combined treatment has higher levels of Bax, Endo G, and cytochrome C of proapoptotic proteins than that of casticin alone and induced lower levels of B‐cell lymphoma 2 (BCL‐2) and BCL‐X of antiapoptotic proteins than that of 5‐FU or casticin only. Furthermore, the combined treatment had a higher expression of cleaved poly (ADP‐ribose) polymerase (PARP) than that of casticin only. Based on these findings, we may suggest that 5‐FU combined with casticin treatment increased apoptotic cell death in WEHI‐3 mouse leukemia cells that may undergo mitochondria and caspases signaling pathways in vitro.     

Hepatic fibrosis does not affect the pharmacokinetics of 5-fluorouracil in rats

In the case of cancer chemotherapy for hepatocellular carcinoma, 5‐fluorouracil (5‐FU) is used widely, and has typically been given by intrahepatic arterial (i.a.) infusion to increase treatment efficacy and to reduce systemic toxicity. 5‐Fluorouracil is eliminated primarily by the liver, and so its use in patients with hepatic disease can be difficult. This study investigated the effect of hepatic fibrosis on the pharmacokinetics of 5‐FU in rats. Experimental hepatic fibrosis was induced by carbon tetrachloride treatment. 5‐Fluorouracil was infused for 15 min into the hepatic artery or the saphenous vein of the rats at a dose of 1.25 mg/kg. There were no significant differences in the plasma concentration and AUC of 5‐FU between hepatic disease rats and their controls after both intravenous and intraarterial injection. This result is probably attributed to the fact that there were no significant differences in hepatic blood flow and dihydropyrimidine dehydrogenase (DPD; an initial and rate‐limiting enzyme in 5‐FU catabolism) activity between hepatic disease rats and their controls, because the total clearance of 5‐FU after intravenous and intraarterial administration is mainly limited by hepatic blood flow and DPD activity, respectively. In conclusion, the pharmacokinetics of 5‐FU is not affected by hepatic fibrosis, unlike that of many hepatically metabolized drugs. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of glutathione S‐transferase genetic polymorphisms on busulfan pharmacokinetics and veno‐occlusive disease in hematopoietic stem cell transplantation: A meta‐analysis

This meta‐analysis was conducted to derive an integrated conclusion about the influence of glutathione S‐transferase (GST) genetic polymorphisms on busulfan pharmacokinetic (PK) parameters and veno‐occlusive disease (VOD). Studies which analysed the effect of GST genetic polymorphisms on area under the curve (AUC), clearance (CL) or VOD were searched for and selected. A pooled analysis was conducted using Comprehensive Meta‐Analysis programme. Nineteen studies were included in this meta‐analysis. GSTA1*B and GSTM1 null genotypes significantly decreased CL_IV of busulfan (standardized difference in means (SDM) = ?1.103; P = 0.019 and SDM = ?0.418; P = 0.002, respectively). GSTA1*B significantly increased AUC_IV of busulfan (SDM = 0.832; P = 0.046), whereas GSTM1 did not (SDM = 0.155; P = 0.478). The PK parameters of oral busulfan did not differ according to GST genotype. GSTA1, GSTM1 and GSTP1 were not significantly associated with VOD occurrence. GSTA1 and GSTM1 genotypes affected CL_IV of busulfan, but only GSTA1 affected AUC_IV. There was no significant difference in the PK parameters of oral busulfan (CL_PO and AUC_PO) and VOD when only GST genotypes were considered.     

Dose-dependent pharmacokinetics of a new reversible proton pump inhibitor, DBM-819, after intravenous and oral administration to rats: hepatic first-pass effect.

The dose-dependent pharmacokinetic parameters of DBM-819 were evaluated after intravenous (5, 10 and 20 mg/kg) and oral (10, 20 and 50 mg/kg) administrations of the drug to rats. The hepatic first-pass effect was also measured after intravenous and intraportal administrations of the drug, 10 mg/kg, to rats. After intravenous administration, the dose-normalized (based on 5 mg/kg) area under the plasma concentration-time curve from time zero to time infinity, AUC, at 20 mg/kg (27.0 and 45.8 microg min/ml) was significantly greater than that at 5 mg/kg due to saturable metabolism. After oral administration, the dose-normalized (based on 10 mg/kg) AUC(0-12 h) at 50 mg/kg (25.1, 18.3 and 49.2 microg min/ml) was significantly greater than those at 10 and 20 mg/kg again due to saturable metabolism. After oral administration of DBM-819, 10 mg/kg, 2.86% of oral dose was not absorbed and the extent of absolute oral bioavailability (F) was estimated to be 46.7%. After intraportal administration of DBM-819, 10 mg/kg, the AUC was 51.9% of intravenous administration, suggesting that approximately 48.1% was eliminated by liver (hepatic first-pass effect). The considerable hepatic first-pass effect of DBM-819 was also supported by significantly greater AUC of M3 (3.70 and 6.86 microg min/ml), a metabolite of DBM-819, after intraportal administration. The AUCs of DBM-819 were not significantly different (comparable) between intraportal and oral administrations of the drug, 10 mg/kg, suggesting that gastrointestinal first-pass effect of DBM-819 was almost negligible in rats. At 10 mg/kg oral dose of DBM-819, the hepatic first-pass effect was approximately 48.1%, F was approximately 46.7 and 2.86% was not absorbed from gastrointestinal tract in rats.     

吲哚美辛对5-氟尿嘧啶在大鼠体内药代动力学的影响

目的探讨吲哚美辛(Ind)增强5-氟尿嘧啶(5-Fu)的抗肿瘤作用是否与药代动力学的变化有关。方法采用反相高效液相色谱(HPLC)法测定大鼠血浆中5-Fu浓度,数据用“3p97”程序处理。结果单用和联用Ind后,5-Fu在大鼠体内的药代动力学均为一室模型,t1/2ka分别为(3.8±2.0)和(4.4±2.7)min,t1/2ke分别为(57±46)和(101±48)min,ke分别为(0.018±0.010)和(0.009±0.005)min-1,cmax分别为(7.0±1.8)和(19±8)mg.L-1,AUC分别为(0.7±0.5)和(3.5±2.4)g.min.L-1,Cl分别为(100±50)和(24±21)mg.kg-1.min-1。说明联用Ind后,5-Fu的作用时间延长,在大鼠体内的经时过程增长。结论Ind能延缓5-Fu在大鼠体内的消除,两者联用时应注意调整给药剂量和对5-Fu进行临床给药监测。     

Preparation and characterization of 5‐fluorouracil‐loaded poly(ϵ‐caprolactone) microspheres for drug administration

Microspheres of 5‐fluorouracil‐loaded poly(?‐caprolactone) (PCL) were prepared by spray‐drying procedure. The degradation characteristics and 5‐fluorouracil release in vitro as well as in vivo were investigated. The average molecular weight, weight loss, crystallinity, and morphology of microspheres were determined using GPC, DSC, and SEM, at different times during the in vitro degradation process. The size distribution of the microspheres indicated that most of the particles were smaller than 3 µm. A 30% weight loss as well as an increase of crystallinity were observed on day 330 of incubation. The percentage of entrapment efficiency of 5‐FU was 49% (44 µg of drug/mg of microspheres). The in vitro total release of 5‐FU took place in 8 days. Determination of plasma 5‐FU concentration in vivo using s.c. injection of 5‐FU‐loaded microspheres in Wistar rats by HPLC with analysis of data using a non‐compartmental model showed drug in plasma 18 days after administration with a maximum drug concentration of 1.5 µg/ml at 96 h. Pharmacokineticallly, a significant increase of AUC and MRT of 5‐FU with regard to the administration of the drug in solution. Scanning electron microscopy and histological studies indicated that the microspheres were surrounded by connective tissue and inflammatory processes were not evident. As a result of these characteristics, the 5‐FU‐loaded PCL microspheres could be used for drug delivery. Drug Dev Res 63:41–53, 2004. © 2004 Wiley‐Liss, Inc.     

Overexpression of miR‐138‐5p suppresses MnCl2‐induced autophagy by targeting SIRT1 in SH‐SY5Y cells

The mechanism of manganism caused by manganese (Mn), an important environmental risk factor for Parkinson's disease, is still unclear. Recent evidence suggested that autophagy participated in neurodegenerative diseases, in which microRNA played a crucial role. However, roles of microRNA in the aberrant autophagy that occurs in neurodegenerative diseases remains controversial. In nervous system, miRNA‐138‐5p is highly expressed and plays a key role in regulating memory and axon regeneration. Importantly, we also found that miR‐138‐5p expression decreased significantly after SH‐SY5Y cells exposed to manganese chloride (MnCl₂) in previous study. To explore the role of miR‐138‐5p in Mn‐induced autophagy, autophagy associated indicators were detected. And we found that MnCl₂ could induce autophagic dysregulation and inhibit expression of miR‐138‐5p. While the levels of LC3‐II/LC3‐I, Beclin1, and p62, the number of autophagosome formation significantly decreased after miR‐138‐5p over‐expression, which demonstrated that miR‐138‐5p could clearly retard Mn‐induced autophagy. In additional, we found there were classical and evolutionarily conserved miR‐138‐5p binding sites in 3′‐UTR region of SIRT1, which was inhibited when overexpression of miR‐138‐5p. Therefore, it was speculated that elevated expression of SIRT1 may be resulted from inhibition of miR‐138‐5p after cells exposed to MnCl₂. Finally, we found that SIRT1 inhibitor EX‐527 suppressed Mn‐induced autophagy as well as miR‐138‐5p, while the suppression was reversed by SIRT1‐specific activator SRT1720. These results indicated that overexpression of miR‐138‐5p suppressed Mn‐induced autophagy by targeting SIRT1.     

Solid‐Supported Synthesis and 5‐HT7/5‐HT1A Receptor Affinity of Arylpiperazinylbutyl Derivatives of 4,5‐dihydro‐1,2,4‐triazine‐6‐(1H)‐one

A series of arylpiperazinylbutyl derivatives of 4,5‐dihydro‐1,2,4‐triazine‐6(1H)‐ones was designed and synthesized according to the new solid‐supported methodology. In this approach, triazinone scaffold was constructed from the Fmoc‐protected glycine. The library representatives showed different levels of affinity for 5‐HT₇ and 5‐HT_1A receptors; compounds 13 , 14 and 18 – 20 were classified as dual 5‐HT₇/5‐HT_1A receptors ligands. The structure–affinity relationship analysis revealed that the receptor affinity and selectivity of the tested compounds depended on the kind of substituent in position 3 of triazinone fragment as well as substitution pattern of the phenylpiperazine moiety.     

Effects of obesity induced by high‐fat diet on the pharmacokinetics of nelfinavir,a HIV protease inhibitor,in laboratory rats

The effect of obesity induced by a high‐fat diet on the pharmacokinetics (PK) of nelfinavir (NFV) was investigated, focusing on the change of distribution and elimination caused by dyslipidemia and hepatic steatosis. The plasma unbound fraction (f_u) of NFV in obese rats (0.61±0.03%) was significantly lower than in the control (1.10±0.09%), caused by increasing the plasma triglyceride‐rich lipoprotein level. After intravenous (i.v.) administration of NFV, the marked decrease of the distribution volume and slower total clearance (39.5% and 69.1% of the control, respectively) caused by the lower f_u were the main reasons for the significantly higher area under the blood concentration versus time curve (AUC) in obese rats (145.3% of the control). The absorption of NFV after intraduodenal (i.d.) administration in obese rats was significantly greater than in the control (AUC; 170.4% of the control). The increased bile in obese rats was the main reason for the increasing absorption of NFV, and the lower expression of intestinal P‐glycoprotein was also considered. On the other hand, although higher AUCs in obese rats were shown, unbound AUCs in the obese rats were slightly lower than in the control, namely, the plasma NFV concentration in obese rats to obtain the same pharmacological effect was higher than in the control, suggesting the difficulty of drug monitoring. These results suggest that it is necessary to pay further attention to therapeutic drug monitoring of NFV in patients manifesting metabolic syndrome, such as dyslipidemia and visceral fat accumulation, including hepatic steatosis. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of deoxyadenosine‐5′‐(35S)‐thiomonophosphate [dAMP(35S)] of high specific activity – a key intermediate for the synthesis of Sp‐deoxyadenosine‐5′‐(alpha;‐35S)‐thiotriphosphate [Sp‐dATP (α‐35S)]

Unprotected deoxyadenosine 1 was treated with an excess of phosphorus acid and stoichiometric proportions of N, N′‐di‐p‐tolylcarbodiimide in anhydrous pyridine to give deoxyadenosine‐5′‐monophosphite 2 . The latter was activated with trimethylsilyl chloride followed by sulphurisation with elemental ³⁵S (specific activity>1000 Ci/mmol) in toluene solution to give deoxyadenosine‐5′‐(³⁵S)‐thiomonophosphate [dAMP(³⁵S)] 3 . Enzymatic conversion of deoxyadenosine‐5′‐(³⁵S)‐thiomonophosphate to Sp‐deoxyadenosine‐5′‐(α‐³⁵S)‐thiotriphosphate [Sp‐dATP (α‐³⁵S)] 5 was carried out following a standard reaction protocol. Copyright © 2001 John Wiley & Sons, Ltd.