Determination of a new phosphodiesterase V inhibitor, DA-8159, in plasma and urine by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method using liquid-liquid extraction for sample preparation was developed for the determination of a new phosphodiesterase V inhibitor, DA-8159, in rat plasma and urine using sildenafil citrate as an internal standard. A 100 microl aliquot of 0.1 M Na(2)CO(3) (containing sildenafil citrate, 3 microg/ml as free sildenafil) and a 1 ml aliquot of ether were added to a 100 microl aliquot of biological samples (urine samples were diluted 20 times with distilled water). After vortex centrifugation at 9000 x g for 3 min, the ether layer was collected and dried under nitrogen gas. The residue was reconstituted with a 150 microl aliquot of the mobile phase, centrifuged, and a 100 microl aliquot of the supernatant was injected onto a reversed-phase column. The mobile phases, 20 mM KH(2)PO(4) (pH 4.7):acetonitrile (70:30, v/v for plasma and tissue samples, and 75:25, v/v for urine samples), were run at a flow rate of 1.0 ml/min. The column effluent was monitored by an ultraviolet detector set at 292 nm. The retention times for DA-8159 and the internal standard were approximately 10.7 and 9.1 min, respectively, in plasma and tissue samples and the corresponding values in urine samples were 47 and 33 min. The detection limits for DA-8159 in rat plasma and urine were 20 and 100 ng/ml, respectively. The coefficients of variation of the assay were generally low: below 10% for plasma and 9.9% for urine. No interferences from endogenous substances were found.

Determination of a new isoquinolinedione derivative, 7-anilino-5,8-isoquinolinedione, in plasma, urine and tissue homogenates by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method was developed for the determination of a new isoquinolinedione derivative, 7-anilino-5,8-isoquinolinedione (IQO4), in rat plasma, urine, blood and tissue homogenates using diazepam as an internal standard. A 2 volume of acetonitrile was added to deproteinize the biological sample. A 50 microl aliquot of the supernatant was injected onto a C(18) reversed-phase column. The mobile phase, 0.05 M acetate buffer (pH 3):acetonitrile:methanol (40:40:20, v/v/v), was run at a flow rate of 1.5 ml/min. The column effluent was monitored using an ultraviolet detector set at 298 nm. The retention times for IQO4 and the internal standard were approximately 5 and 7 min, respectively. The detection limits of IQO4 in rat plasma, urine and tissue homogenates (including blood) were 0.05, 0.1 and 0.1 microg/ml, respectively. The coefficients of variation of the assay were below 9.4% for rat plasma, urine and tissue homogenates. No interferences from endogenous substances were found.

Determination of a new reversible proton pump inhibitor, DBM-819, in human plasma and urine, and rat tissue homogenates by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method was developed for the determination of a new proton pump inhibitor, DBM-819, in human plasma and urine and rat tissue homogenates using KR-60461 as an internal standard. A 100-microl aliquot of acetonitrile (containing 0.5 microg/ml of the internal standard) and a 200-microl aliquot of 0.1 M Na(2)HPO(4) (adjusted pH 11 with 1 N NaOH) were added to a 100-microl aliquot of biological sample. After vortex-mixing, the mixture was extracted with 1 ml of ethylacetate. After centrifugation at 12000 x g for 3 min, the organic layer was collected and evaporated under nitrogen gas. The residue was then reconstituted with a 100-microl aliquot of mobile phase, and a 40-microl aliquot was injected onto the HPLC column. The mobile phase, 0.02 M phosphate buffer (pH 5): acetonitrile: methanol (46:44:10, v/v/v), was run at a flow rate of 0.5 ml/min and the column effluent was monitored by the fluorescence detector set at an excitation wavelength of 340 nm and an emission wavelength of 470 nm. The retention times for DBM-819 and the internal standard were approximately 10.5 and 12 min, respectively. The detection limits of DBM-819 in human plasma and urine, and rat tissue homogenates were 0.01, 0.02 and 0.02 (or 0.05) microg/ml. respectively. The coefficients of variation (CV) of the assay were below 11% for human plasma and urine, and rat tissue homogenates. No interferences from endogenous substances were found.

Effects of water deprivation for 72 hours on the pharmacokinetics of a new carbapenem, DA-1131, in rats

Hormonal, physiological, and biochemical changes occurring in dehydrated patients could alter the pharmacokinetics of the drugs; therefore, the pharmacokinetics of DA-1131, a new carbapenem antibiotic, were investigated after 1-min intravenous administration of the drug at 50 mg/kg to control and 72-hr water-deprived rats. The impaired kidney and liver functions were observed in water-deprived rats on the basis of tissue microscopic examination. After intravenous infusion of the drug to water-deprived rats, the plasma concentrations of DA-1131 were higher and this resulted in a significantly greater total area under the plasma concentration-time curve from time zero to time infinity than those in control rats (4520 versus 3760 microg min/ml). This could be due to significantly slower total body clearance (CL) of DA-1131 in water-deprived rats (9.81 versus 14.1 ml/min/kg). The significantly slower CL of DA-1131 in water-deprived rats was due to significant decrease in both renal clearance (2.87 versus 5.13 ml/min/kg because of a significant decrease in 8-hr urinary excretion of unchanged DA-1131 [28.4 versus 39.9% of the intravenous dose] due to impaired kidney function) and nonrenal clearance (6.82 versus 8.66 ml/min/kg because of a significant decrease in the metabolism of DA-1131 in the kidney, as proved by the significant decrease in total renal DHP-I enzyme activity [1900 versus 2130 mU/each kidney]) in water-deprived rats. Water-deprivation did not alter the affinity of rat tissues to DA-1131.

Pharmacokinetics, stability, and blood partition of DA-8159, a new phosphodiesterase V inhibitor

The pharmacokinetics of DA-8159, a new phosphodiesterase V inhibitor, after 1 min intravenous, 30 mg/kg, and oral, 30 mg/kg, administration of the drug to rats, the stability of DA-8159 in various pH solutions ranging from 1 to 13, and human and rat plasma and urine, and the blood partition of DA-8159 between plasma and blood cells of rabbit were evaluated. After intravenous administration, DA-8159 was eliminated fast with the mean total body clearance of 126 ml/min/kg, and was almost completely metabolized in rats; 5.98% of intravenous dose of DA-8159 were excreted unchanged in 24-hr urine. The extent of absolute oral bioavailibility of DA-8159 was approximately 25%. The apparent volume of distribution at steady state was considerably large, 15048 ml/kg, suggesting that DA-8159 has a good affinity to rat tissues. DA-8159 was relatively stable in various pH solutions, and human and rat plasma and urine for up to 48 h incubation in a water-bath shaker kept at 37 degrees C and at a rate of 50 oscillations per min. DA-8159 reached equilibrium fast (within 30 sec mixing manually) between plasma and blood cells of rabbit blood and the plasma-to-blood cell concentration ratios were independent of initial blood concentrations of DA-8159, 1, 5, and 10 microg/ml, when the rabbit whole blood was incubated for up to 120 min; the ratios were in the range of 0.662-0.812. There was no in vitro 'blood storage effect' in the plasma concentration of DA-8159.

Factors influencing the protein binding of IQO4, a new isoquinolinedione derivative

Various factors most likely to influence the plasma protein binding of IQO4, a new isoquinolinedione derivative, to 4% human serum albumin (HSA) were evaluated using an equilibrium dialysis technique at an initial IQO4 concentration of 5 microg/ml. It took approximately 12 h incubation to reach an equilibrium between 4% HSA and isotonic Sørensen phosphate buffer at pH 7.4 containing 3% dextran ('the buffer') using a Spectra/Por 2 membrane (molecular weight cut-off, 12000-14000) in a water-bath shaker kept at 37 degrees C and at a rate of 50 oscillations per min. IQO4 was stable both in 4% HSA and in 'the buffer' for up to 24 h incubation at 37 degrees C. The binding of IQO4 was constant (89.9 +/- 1.40%, mean +/- standard deviation) at IQO4 concentrations ranging from 1 to 100 microg/ml. However, the extent of binding was dependent on HSA concentrations. The values were 32.5, 62.0, 79.1, 84.9, 90.9, 91.2, and 91.7% at HSA concentrations of 0.5, 1, 2, 3, 4, 5, and 6%, respectively; on incubation temperature, 96.7, 93.8, and 91.0% when incubated at 4, 22, and 37 degrees C, respectively; and on the buffer pHs, 84.4, 87.2, 88.2, 90.9, and 92.3% for the buffer pHs of 5.8, 6.4, 7, 7.4, and 8, respectively. The free fraction of IQO4 increased with the addition of sulfisoxazole (0-300 microg/ml), and salicylic acid (0-300 microg/ml). The protein binding of IQO4 was independent of the quantity of alpha-1-acid glycoprotein (up to 0.32%), chloride ion (up to 0.546%) and heparin (up to 40 units/ml).

Effects of neostigmine on the pharmacokinetics of intravenous parathion in rats

It was reported that the area under the plasma concentration-time curve from time zero to time infinity (AUC) of parathion was significantly smaller and the time-averaged total body clearance (CL) of parathion was significantly faster after intravenous administration of parathion to rats pretreated with dexamethasone than those in control rats. This was supported by significantly faster intrinsic clearance of parathion to form paraoxon in hepatic microsomal fraction of rats pretreated with dexamethasone. The above data suggested that parathion was metabolized to paraoxon by dexamethasone-inducible hepatic cytochrome P450 (CYP) 3A in rats. The purpose of this study is to explain the protective effects of neostigmine against paraoxon toxicity by suppressing CYP3A and hence decreasing formation of toxic metabolite, paraoxon by neostigmine. The pharmacokinetic changes of parathion and its active metabolite, paraoxon, were investigated after intravenous administration of parathion, 3 mg/kg, to control Sprague-Dawley rats and the rats pretreated with neostigmine (200 microg/kg, intraperitoneal injection 30 min before parathion administration). After 1-min intravenous infusion of parathion to rats pretreated with neostigmine, the AUC of parathion (65.1 versus 74.3 microg min/ml) was significantly greater and the CL of parathion (45.1 versus 40.4 ml/min/kg) was significantly slower than those in control rats. Based on in vitro hepatic microsomal studies, neostigmine inhibited significantly the erythromycin N-demethylase activity (1.03 versus 0.871 nmol/mg protein/min), mainly mediated by hepatic cytochrome P450 3A in rats. The above data suggested that the formation of paraoxon was inhibited in rats pretreated with neostigmine by inhibiting CYP3A.

Comparative study of three-dimensional and conventional endorectal ultrasonography used in rectal cancer staging

BACKGROUND

Three-dimensional (3D) imaging offers improved knowledge of various anatomic structures and tumors by providing 3D images. This prospective study was performed to verify whether 3D endorectal ultrasonography (EUS) enhances the accuracy of rectal cancer staging, as compared with conventional EUS.

METHODS

Using both 3D and conventional EUS, 33 consecutive patients with operable rectal cancer were preoperatively staged. A rigid 3D probe with a scanner was used for 3D EUS, and a rigid endorectal probe with a scanner was used for conventional EUS.

RESULTS

The accuracy of 3D EUS was 90.9% for pT2 and 84.8% for pT3, whereas that of conventional EUS was 84.8% and 75.8%, respectively, thereby showing no difference between these two methods. The lymph node metastasis was accurately predicted by 3D EUS in 28 patients (84.8%), whereas conventional EUS predicted the disorder in 22 patients (66.7%). The difference was not statistically significant. The average infiltration grade of the circumference on transverse 3D EUS scans was associated closely with advancement of the TNM stage (p <0.001-0.006) and lymph node metastasis (p = 0.003). The presence of a cone-shaped surface on the deep tumor border correlated with the infiltration grade shown on all of the sectional displays (p <0.001-0.042) and with advancement of the TNM stage (p = 0.018).

CONCLUSIONS

Although the findings did not show 3D EUS to have a significant advantage over conventional EUS for the accurate evaluation of rectal cancer, a numeric advantage may possibly be statistically significant in a further study with larger cases. Furthermore, stereoscopic visualization provided easier and complete understanding of both focal lesions and lymph nodes.

Bradykinin-12-lipoxygenase-VR1 signaling pathway for inflammatory hyperalgesia

The capsaicin-sensitive vanilloid receptor (VR1) was recently shown to play an important role in inflammatory pain (hyperalgesia), but the underlying mechanism is unknown. We hypothesized that pain-producing inflammatory mediators activate capsaicin receptors by inducing the production of fatty acid agonists of VR1. This study demonstrates that bradykinin, acting at B2 bradykinin receptors, excites sensory nerve endings by activating capsaicin receptors via production of 12-lipoxygenase metabolites of arachidonic acid. This finding identifies a mechanism that might be targeted in the development of new therapeutic strategies for the treatment of inflammatory pain.

Increase in urea in conjunction with L-arginine metabolism in the liver leads to induction of cytochrome P450 2E1 (CYP2E1): the role of urea in CYP2E1 induction by acute renal failure

A number of xenobiotics and certain pathophysiological situations cause the induction of CYP2E1. The present study was designed to establish the role of plasma urea nitrogen and L-arginine on hepatic CYP2E1 expression in rats or rats with acute renal failure. Exposure of rats to a single intravenous dose of 5 mg/kg uranyl nitrate caused renal failure in 5 days (ARF), as evidenced by increases in plasma urea nitrogen level and kidney to body weight ratio. Northern and Western blot analyses revealed that hepatic CYP2E1 was 2- to 4-fold induced by ARF. Treatment of rats with either 10% glucose in drinking water for 5 days following a single injection of uranyl nitrate or two injections of recombinant growth hormone (5 units/kg, s.c., twice a day) on the 4th day after uranyl nitrate injection reduced both the rise in plasma urea nitrogen and the induction of CYP2E1. Exposure of rats to urea (approximately 225 mg/kg/day) in drinking water for 1 to 3 day(s) resulted in significant increases in CYP2E1 mRNA and protein. Furthermore, perfusion of the liver with 25 mM urea for 24 h resulted in CYP2E1 induction with an increase in the mRNA. The levels of CYP2E1 protein and mRNA were increased in rats perfused with 25 mM L-arginine for 24 h (i.e., a 4-fold increase). Hence, L-arginine, which is irreversibly hydrolyzed to urea and ornithine by arginase, also induced hepatic CYP2E1. The results of the present study provided evidence that increases in plasma urea in conjunction with L-arginine metabolism lead to the induction of CYP2E1 in the liver.

Pharmacokinetics of ipriflavone, an isoflavone derivative, after intravenous and oral administration to rats hepatic and intestinal first-pass effects

Pharmacokinetic parameters of ipriflavone were evaluated after intravenous administration of spray-dried ipriflavone with polyvinylpyrrolidone, SIP (5, 10, 20, and 40 mg/kg as ipriflavone) and oral administration of SIP (50, 100, and 200 mg/kg as ipriflavone) to rats. The hepatic, gastric, and intestinal first-pass effects of ipriflavone were also measured after intravenous, intraportal, intraduodenal, and oral administration of SIP (20 or 50 mg/kg as ipriflavone) to rats. After intravenous and oral administration, the pharmacokinetic parameters of ipriflavone were dose-independent. The extent of absolute oral bioavailability (F) was also independent of oral doses; the mean F value was approximately 24%. Considering the amount of unchanged ipriflavone recovered from 24-hr gastrointestinal tract (the mean value was approximately 12%), the low F values could be due to the hepatic, gastric, and/or intestinal first-pass effects. Based on total body clearance (CL) data of ipriflavone after intravenous administration, the first-pass effect in the heart and lung could be almost negligible, if any, in rats. Approximately 30% of ipriflavone absorbed into the portal vein was eliminated by liver (hepatic first-pass effect) based on intravenous and intraportal administration of SIP. The area under the plasma concentration-time curve from time zero to time infinity (AUC) values after oral administration and intraduodenal instillation of SIP, 50 mg/kg as ipriflavone, were not significantly different, but the values were significantly smaller (129 and 116 microg ml/min) than that after intraportal administration of SIP, 20 mg/kg as ipriflavone (513 microg ml/min based on 50 mg/kg), indicating that gastric first-pass effect of ipriflavone was negligible, but intestinal first-pass effect was considerable in rats. Therefore, the low F value of ipriflavone after oral administration to rats was mainly due to intestinal first-pass effect. The hepatic first-pass effect and incomplete absorption of ipriflavone from rat gastrointestinal tract could also contributed to the low F in rats.

Identification of genes enhanced by protein-calorie malnutrition by differential display polymerase chain reaction (expression of fibrinogen B beta chain, B cell translocation gene 1 and thyroid hormone responsive protein genes)

Protein-calorie malnutrition (PCM), as one of global health problems, arises during protein and/or energy deficit due to disease and nutritional inadequacy. Previously, we showed that PCM elicited oxidative stress with activation of the phase II detoxifying gene expression, which was reversed by cysteine supplementation. As part of the attempts to identify the cellular adaptive responses and the associated gene expression during PCM, the current study was initiated to analyze the genes differentially expressed in the rat during PCM. Among 1,916 bands amplified, 85 putative differentially amplified bands were enhanced by PCM in the liver, while the expression of 64 bands was suppressed. Northern and/or reverse transcription-polymerase chain reaction (RT-PCR) analyses revealed that PCM increased the expression of fibrinogen B beta chain, B cell translocation gene I (BTGI) and thyroid hormone responsive protein (THRP) mRNAs. The increase in the hepatic fibrinogen B beta chain mRNA was not prevented by cysteine supplementation, whereas cysteine decreased the enhancement in the rGSTA2 and microsomal epoxide hydrolase mRNA expression. Cysteine was also active in reversing the increase in BTG1 mRNA during PCM. This was supported by the increase in BTG1 mRNA in H4IIE cells exposed to sulfur amino acid-deprived medium. Northern blot analysis revealed that THRP, highly expressed in the brain in a tissue-specific manner, was induced by PCM and that cysteine supplementation abolished the THRP induction. Conversely, the level of hepatic albumin mRNA was markedly decreased by PCM, which was partially restored by cysteine supplementation. Differential display RT-PCR analysis allowed us to identify the genes that are responsive to oxidative stress during PCM and to characterize the differential role of cysteine on the expression of the fibrinogen B beta chain, BTG1 and THRP genes as a homeostatic adaptive response during protein deficiency.

The transport of a hepatoprotective agent, isopropryl 2-(1-3-dithiethane-2-ylidene)-2[N-(4-methyl-thiazole-2-yl) carbamoyl] acetate (YH439), across Caco-2 cell monolayers

Isopropryl 2-(1-3-dithiethane-2-ylidene)-2[N-(4-methyl-thiazole-2-yl) carbamoyl] acetate (YH439) is currently under phase II clinical trials by the Yuhan Research Center for use as a hepatoprotective agent. Unfortunately, the oral bioavailbility of YH439, which is sparingly soluble in water (i.e., 0.3 microg/ml or 0.91 microM at room temperature), reportedly, is negligible regardless of the dose administered to rats in the 10-300 mg/kg range. The bioavailability of the compound increased up to 24%, when administered in the form of a micellar solution (700 microg/ml or 2.1 mM for YH439) at a dose of 10 mg/kg, suggesting that its limited solubility is associated with its negligible bioavailability. In order to obtain additional information concerning the bioavailability of YH439, the mechanism(s) involved in gastrointestinal (GI) absorption were investigated in the present study. For this purpose, the transport of YH430 across a Caco-2 cell monolayer was measured in a Transwell. A permeability of 4.07 x 10(-5) cm/s was obtained for the absorptive (i.e., apical to basolateral direction) transport of 0.42 pM YH439, implicating that the in vivo GI absorption is nearly complete. The absorptive transport exhibited a slight concentration-dependency with an intrinsic clearance (CLi) of 0.38 microLL/cm2/sec, which accounted for 28.1% of the total intrinsic clearance (i.e., CLi plus the intrinsic clearance for the linear component) of the transport. Thus, saturation of the absorption process appears to be a minor factor in limiting the bioavailability of the compound. The apparent permeability of YH439 from the basolateral to the apical direction (i.e., efflux, 6.67 x 10(-5) cm/s) was comparable to that for absorptive transport, but, interestingly, a more distinct concentration-dependency was observed for this transport. However, the efflux does not appear to influence the bioavailability of the compound, as evidenced by the sufficiently high permeability in the absorption direction. Rather, a reportedly extensive first-pass hepatic metabolism appears to be a principal factor in limiting the bioavailability. In this respect, reducing the first-pass metabolism by some means would lead to a higher bioavailability of the compound. Thus, elevation of the absorption rate of YH439 becomes a necessity. From a practical point of view, increasing the concentration of YH439 in the GI fluid appears to be a feasible way to increase the absorption rate, because the compound is primarily absorbed via a linear mechanism. In summary, the solubilization of YH439, as previously demonstrated for a micellar solution of the compound, appears to be a practical way to increase the oral bioavailability of YH439.

Effects of cysteine on the pharmacokinetics of intravenous phenytoin in rats with protein-calorie malnutrition

The effects of cysteine on the pharmacokinetics of phenytoin and one of its metabolites, 5-(p-hydroxyphenyl)-5-phenylhydantoin (pHPPH) were investigated after intravenous administration of phenytoin, 25 mg/kg, to control rats (4-week fed on 23% casein diet) and rats with PCM (protein-calorie malnutrition, 4-week fed on 5% casein diet) and PCMC (PCM with oral cysteine supplementation, 250 mg/kg, twice daily starting from the fourth week). In rats with PCM and PCMC, the phenytoin hydroxylation (to form pHPPH) activities were significantly smaller (164, 103 and 95.3 pmol/min per mg protein for the control rats, and rats with PCM and PCMC, respectively) than that in control rats. In rats with PCMC, the intrinsic clearance of phenytoin, CL(int) was significantly slower than those in control rats and rats with PCM (0.175, 0.131 and 0.044 ml/min). The above data suggested that the formation of pHPPH could be reduced in rats with PCM and PCMC. This was supported by significantly smaller 24-h urinary excretion of pHPPH (54.7, 35.6 and 32.5% of intravenous dose of phenytoin) in rats with PCM and PCMC than that in control rats. In rats with PCM, the maximum velocity (0.344, 0.203 and 0.196 microg/min), apparent volume of distribution in central compartment (44.4, 65.4 and 72.2 ml/kg) of phenytoin, and total area under the plasma concentration-time curve from time zero to time infinity (609, 714 and 1210 microg min/ml), renal clearance (20.5, 13.4 and 4.67 ml/min per kg) and 24-h urinary excretion (54.7, 35.6 and 32.5% of intravenous dose of phenytoin) of pHPPH were not returned to control levels by cysteine supplementation (rats with PCMC). This could be mainly due to the fact that the phenytoin hydroxylation activity in rats with PCMC was not returned to control level.

Frequent epigenetic inactivation of RASSF1A in human bladder carcinoma

Allelic deletion or transcriptional silencing of RASSF1, a putative tumor suppressor at 3p21.3, has been found in a considerable proportion of lung, breast, and ovarian cancers. In this study, we analyzed the expression and mutation status of three RASSF1 isoforms (-A, -B, and -C) in 55 primary bladder carcinomas and 10 bladder and prostate cancer cell lines. The RASSF1A transcript was not found in 80% (4 of 5) and 100% (4 of 4) of bladder and prostate cell lines, respectively. Compared with normal bladder tissues, loss or significant reduction of RASSF1A was identified in 62% (34 of 55) of primary bladder carcinomas and 10 (83%) of 12 matched sets showed tumor-specific alteration of RASSF1A expression. Moreover, loss or abnormal down-regulation of RASSF1A correlated with advanced tumor stage. RASSF1B was undetectable in 60% (3 of 5) of bladder cell lines and in 31% (17 of 55) of primary tumors, but none of these tumors showed altered expression exclusively in RASSF1B. RASSF1C transcript was detected in all cell lines and primary tumors we examined. Expression of RASSF1A and RASSF1B was reactivated in all nonexpressor cell lines by treatment with the demethylating agent 5-aza-2'-deoxycytidine. Bisulfite DNA sequencing analysis revealed that aberrant hypermethylation at the CpG island in the RASSF1A promoter is strongly associated with the loss of RASSF1A expression in cell lines and uncultured primary tumors. Methylation-specific PCR and BstUI digestion analyses also demonstrated that 97% (33 of 34) of RASSF1A-nonexpressing primary tumors are methylated. Although somatic mutations were not identified in RASSF1 transcripts expressed in unmethylated tumors, 24% (9 of 37) of methylated cell lines and primary tumors showed detectable reductions in genomic levels of RASSF1, suggesting that RASSF1A inactivation might be caused by both epigenetic and genetic mechanisms in a subset of bladder tumors. Together, our data suggest that RASSF1A inactivation may play a critical role in the malignant progression of human bladder carcinomas.

Frequent epigenetic inactivation of RASSF1A by aberrant promoter hypermethylation in human gastric adenocarcinoma

Methylation associated inactivation of RASSF1, a putative tumor suppressor identified at 3p21.3, has been frequently observed in several human malignancies, including lung and breast cancers. To explore the penetrance of RASSF1 in gastric carcinogenesis, we performed expression and mutation analyses of 3 isotypes of RASSF1 (A, B, and C) in 150 gastric specimens, including 15 carcinoma cell lines. RASSF1A and RASSF1B transcripts were not expressed in 60% (9 of 15) and 33% (5 of 15) of gastric carcinoma cell lines, respectively, whereas RASSF1C was detectable in all cell lines. Bisulfite DNA sequencing analysis revealed that the CpG island in the RASSF1A promoter is hypermethylated in all RASSF1A-nonexpressing cell lines. In addition, both RASSF1A and RASSF1B were re-expressed by treatment with the demethylating agent 5-aza-2'-deoxycytidine. Among 90 primary gastric adenocarcinomas examined, 41 (46%) and 19 (21%) expressed no or abnormally low levels of RASSF1A and RASSF1B, respectively, and 12 (13%) tumors showed no expression of both isoforms. Loss or abnormal down-regulation of RASSF1A correlated with tumor stage and grade but not with histological types of tumors. Methylation-specific PCR analysis demonstrated that 95% (39 of 41) of RASSF1A-nonexpressing primary tumors are methylated at the CpG sites in the promoter, whereas none of the adjacent noncancerous or normal tissues are methylated. No somatic mutations were detected in RASSF1 transcripts expressed in unmethylated tumors. However, 10 methylated tumors, including 4 cell lines, showed low genomic levels of RASSF1 and expressed no RASSF1A transcripts, suggesting that RASSF1A inactivation might be caused by both epigenetic and genetic mechanisms in a subset of gastric adenocarcinomas. In conclusion, our data indicate that epigenetic transcriptional silencing of RASSF1, especially RASSF1A isoform, is a frequent event in gastric tumorigenesis and might play an important role in the malignant progression of gastric adenocarcinomas.

Source of errors in the evaluation of early rectal cancer by endoluminal ultrasonography

PURPOSE

Although preoperative evaluation of early rectal cancers can be done by endoluminal sonography and by means of colonoscopic findings, it is still controversial whether endoluminal sonography can effectively discriminate mucosal from submucosal lesions. This study was performed to verify objective causes of errors in the evaluation of early rectal cancer (T0/1) using a review of videotaped endoluminal sonography images.

METHODS

Eighty-nine patients with suspected early rectal cancer on endoluminal sonography were included. Two different scanners with appropriate probes were used according to tumor location, i.e., transrectal ultrasonography was used to scan up to 8 cm of the rectum above the anal verge, whereas endoscopic ultrasonography was used to assess higher lesions. Endoluminal sonography images were correlated with histologic infiltration and were reevaluated carefully to identify sources of errors.

RESULTS

Sensitivity and specificity were 83.1 and 96.5 percent, respectively, for tumor staging, whereas sensitivity was very low compared with specificity (16.7 vs. 90.2 percent) for metastatic lymph nodes. Endoluminal sonography images showed irregularity of the underlying tumor border (P < 0.01) and hypoechoic blurring or cutoff of the inner and outer hypoechoic layers (P < 0.001), all of which closely correlated with histologic infiltration of tumor cells. Overstaging occurred more than twice as often as understaging in tumor reevaluation (14 vs. 5 occurrences). In contrast to tumors, lymph nodes showed a similar amount of both overstaging (four cases) and understaging (five cases). The sources of errors were summarized as five types: false instrumentation, interpretive errors, anatomic defects, imaging failure, and inevitable errors.

CONCLUSIONS

Because false instrumentation, interpretive errors, and anatomic defects were considered preventable, 23 (82.1 percent) of the 28 errors might have been avoided. Therefore, a clear image by endoluminal sonography can effectively distinguish mucosal from submucosal lesions in early rectal cancer.

No effect of water deprivation for 48 hours on the pharmacokiinetics of intravenous tacrolimus in rats

Because the physiological changes that occur in patients with water deprivation could alter the pharmacokinetics of drugs, the pharmacokinetics of tacrolimus were investigated after 1-min intravenous administration of the drug (1 mg/kg) to control rats and rats with water deprivation for 48 h. In rats with dehydration, kidney function seemed to be impaired slightly. Kidney weight (0.800 versus 0.676% body weight) increased significantly and the renal tissue showed only total and mild tubular dilatation and flattening of tubular epithelial cells based on kidney microscopy. However, hepatic function seemed not to be impaired in rats with dehydration. After intravenous administration of tacrolimus, the pharmacokinetic parameters were not significantly different between two groups of rats and the results were expected since tacrolimus was almost completely metabolized in rats (impaired kidney function could not affect considerably the pharmacokinetics of tacrolimus) and hepatic function was not impaired in rats with dehydration.

Bioequivalence of clarithromycin tablet formulations assessed in Korean males

AIM

Determination of the bioequivalence of 2 clarithromycin tablet formulations manufactured in Korea.

PATIENTS AND METHODS

Twenty-four healthy male Korean volunteers received each of the 2 clarithromycin formulations at a dose of 250 mg in a 2 x 2 crossover study. There was a one-week washout period between doses. Plasma concentrations of clarithromycin were monitored by high-performance liquid chromatography over a period of 12 hours after administration. AUCinf (the area under the plasma concentration-time curve from time zero to time infinity) was calculated using the linear-log trapezoidal method. Cmax (maximum plasma drug concentration) and Tmax (time to reach Cmax) were compiled from the plasma concentration-time data. Analysis of variance was carried out using logarithmically transformed AUCinf and Cmax and untransformed Tmax.

RESULTS

The point estimates and 90% confidence intervals for AUCinf (parametric) and Cmax (parametric) were 0.971 (0.886 approximately 1.063) and 0.982 (0.868 approximately 1.107), respectively, satisfying the bioequivalence criteria of the European Committee for Proprietary Medicinal Products and the US Food and Drug Administration guidelines. The corresponding value of Tmax was 0.000 (-0.250 approximately 0.250).

CONCLUSION

These results indicate that the 2 medications of clarithromycin are bioequivalent and, thus, may be prescribed interchangeably.

Determination of a chemopreventive agent, Oltipraz, in rat plasma and urine by high-performance liquid chromatography

A high-performance liquid chromatographic method was developed for the determination of a chemopreventive agent, Oltipraz, in rat plasma and urine. The sample preparation was simple; 2 volumes of acetonitrile were added to deproteinize the biological sample. A 50-microl aliquot of the supernatant was injected onto a C18 reversed-phase column. The mobile phase, acetonitrile : 0.5 mM ammonium acetate (55: 45, v/v for rat plasma and 45 : 55, v/v for rat urine), was run at a flow-rate of 1.5 ml/min. The column effluent was monitored using an ultraviolet detector set at 305 nm. The retention times for Oltipraz in rat plasma and urine were approximately 5.8 and 8.6 min, respectively. The detection limits of Oltipraz in rat plasma and urine were 20 and 50 ng/ml, respectively. The coefficients of variation of the assay (within-day and between-day) were generally low (below 4.65%) in concentration ranges from 0.02 (0.05) to 10 microg/ml for rat plasma and urine. No interference from endogenous substances was found.

CT differentiation of mesenteric ischemia due to vasculitis and thromboembolic disease

PURPOSE

The purpose of this work was to differentiate CT findings of acute mesenteric ischemia due to vasculitis (MV) or thromboembolism (MTE).

METHOD

CT scans of 69 patients with mesenteric ischemia caused by MV (n = 37) or MTE (n = 32) were analyzed. After dividing the patients into groups with and without MV, we compared them with regard to gastrointestinal tract involvement patterns, mesenteric changes, and presence or absence of vascular thrombosis, atherosclerosis, other organ changes, and ascites.

RESULTS

Duodenum was involved only in the MV group (30%). The MV group had preferential involvement of the small intestine (89%) to large intestine (51%), whereas the MTE group showed even distribution. Multisegmental bowel involvement was more common in the MV group (86%) than in the MTE group (44%), especially in both jejunum and ileum and both small and large intestine. The MV group showed prominent involvement of the superior mesenteric vessel territory, although the MTE group showed even distribution. Splenomegaly and hydronephrosis were more frequently seen in the MV group and vascular thrombosis and atherosclerosis in the MTE group.

CONCLUSION

Although considerable overlap was noted, CT is useful in differentiating MV from MTE.

Cl(-)-dependent HCO3- transport by cystic fibrosis transmembrane conductance regulator

Cystic fibrosis (CF) affects the function of multiple organs. The inability to maintain luminal hydration of ducts leads to their plugging and destruction of the affected organs. An exacerbating problem is the acidic pH of the fluid produced by CF patients' secretory glands. This is best documented for pancreatic secretion. Alkaline fluid secretion requires vectorial transport of electrolytes and of HCO(3)(-). The mechanism of HCO(3)(-) secretion by cystic fibrosis transmembrane conductance regulator (CFTR) expressing cells is not well understood. In the present communication we discuss results suggesting that CFTR itself can transport large amounts of HCO(3)(-) and that HCO(3)(-) transport by CFTR is mediated by a coupled, Cl(-)-dependent process that is different from a simple HCO(3)(-) conductance.

Coordination of pancreatic HCO3- secretion by protein-protein interaction between membrane transporters

Increasing evidence suggests that protein-protein interaction is essential in many biological processes including epithelial transport. In this report, we discuss the significance of protein interactions to HCO(3)(-) secretion in pancreatic duct cells. In pancreatic ducts HCO(3)(-) secretion is mediated by cystic fibrosis transmembrane conductance regulator (CFTR) activated luminal Cl(-)/HCO(3)(-) exchange activity and HCO(3)(-) absorption is achieved by Na(+)-dependent mechanisms including Na(+)/H(+) exchanger 3 (NHE3). We found biochemical and functional association between CFTR and NHE3. In addition, protein binding through PDZ modules is needed for this regulatory interaction. CFTR affected NHE3 activities in two ways. Acutely, CFTR augmented the cAMP-dependent inhibition of NHE3. In a chronic mechanism, CFTR increases the luminal expression of Na(+)/H(+) exchange in pancreatic duct cells. These findings reveal that protein complexes in the plasma membrane of pancreatic duct cells are highly organized for efficient HCO(3)(-) secretion.