Chiyuki Yamato

Comparison of the kinetic disposition and metabolism of E3810, a new proton pump inhibitor, and omeprazole in relation to S‐mephenytoin 4′‐hydroxylation status

We studied the kinetic disposition and metabolism of E3810 [(±)‐sodium 2‐[[4‐(3‐methoxypropoxy)‐3‐methylpyridin‐2‐yl]methylsulfinyl]‐1H‐benzimidazole], a new proton pump inhibitor, and omeprazole in 15 Japanese male volunteers, six of whom were poor metabolizers and nine of whom were extensive metabolizers of S‐mephenytoin. All received once‐daily 20 mg doses of E3810 or omeprazole for 7 days in a randomized crossover manner, with a 3‐week washout period between the two trial phases. The parent drugs and their principal metabolites in plasma and urine were measured on days 1 and 7 after drug administration. The mean values for area under the plasma concentration‐time curve (AUC) of omeprazole were 6.3‐ and 4.4‐fold greater, whereas those of E3810 were 1.8‐ and 1.9‐fold greater in poor metabolizers than in extensive metabolizers after the first and final doses, respectively. Although the mean AUC values for both drugs were significantly (p < 0.01 or p < 0.05) greater in poor metabolizers than in extensive metabolizers, the difference in the AUC between the two groups was smaller after E3810 than after omeprazole administration. The AUC of omeprazole tended to increase with the repeated doses in extensive metabolizers, whereas no such change was observed for E3810. The urinary excretions of the principal metabolite(s) of two proton pump inhibitors also reflected the data derived from plasma samples in relation to S‐mephenytoin 4′‐hydroxylation status. We conclude that the metabolism of two proton pump inhibitors is under coregulatory control of S‐mephenytoin 4′‐hydroxylase (CYP2C19), but that the magnitude of CYP2C19‐mediated metabolism appears to differ between the two drugs. In contrast to omeprazole, the metabolism of E3810 is less saturable in extensive metabolizers during the repetitive dosings.

Comparison of the interaction potential of a new proton pump inhibitor, E3810, versus omeprazole with diazepam in extensive and poor metabolizers of S-mephenytoin 4'-hydroxylation

To compare the interaction potential of E3810, [(±)‐sodium 2‐[[4‐(3‐methoxypropoxy)‐3‐methylpyridin‐2‐yl]methylsulfinyl]‐1H‐benzimidazole] a new proton pump inhibitor, and omeprazole with diazepam in relation to S‐mephenytoin 4′‐hydroxylation status.

Effect of azelastine on the intracellular Ca2+ mobilization in guinea pig peritoneal macrophages.

Azelastine, an orally effective anti-allergic agent, has been demonstrated to inhibit the release of histamine and leukotrienes. This suggests that azelastine might alter the mobilization of intracellular Ca2+. We have examined the effect of azelastine on the change in intracellular free calcium concentration ([Ca2+])i) in guinea pig peritoneal macrophages induced by platelet activating factor (PAF-acether) or N-formylmethionyl-leucyl-phenylalanine (FMLP) using a fluorescent Ca2+ indicator, fura2. PAF-acether raised [Ca2+]i from 89 +/- 4 to 243 +/- 26 nM (n = 15) within 20 s after addition of PAF-acether in the presence of 2 mM EGTA. This indicates that the stimulation of macrophages by PAF-acether induced intracellular mobilization of Ca2+, and pretreatment with azelastine reduced the PAF-acether-induced increase in [Ca2+]i in a dose-dependent manner (IC50 = 16 microM). Azelastine also inhibited the FMLP-induced increase in [Ca2+]i. Furthermore, PAF-acether and FMLP both caused the release of prostaglandin E2 from macrophages, and pretreatment with azelastine reduced the PGE2 release dose dependently (IC50 = 10 microM). These results suggest that azelastine inhibits the release of Ca2+ from intracellular storage sites induced by PAF-acether or FMLP, and that this effect possibly causes reduction in the release of PGE2 from the cells.

Calcitonin Gene‐Related Peptide‐Binding Sites of Porcine Cardiac Muscles and Coronary Arteries: Solubilization and Characterization

Abstract: Calcitonin gene‐related peptide (CGRP)‐binding sites were solubilized, using digitonin, from the porcine spinal cord, atria, and coronary arteries. The specific binding of 125I‐human α‐CGRP to the solubilized binding sites was inhibited by human α‐ and β‐CGRP and by rat α‐CGRP, but not by angiotensin II or human calcitonin. Scatchard plot analysis of saturation gave the same KD value for CGRP in the crude membrane fractions of the tissues examined. The affinity of CGRP to the binding sites was decreased by solubilization in the atria and coronary arteries, but not in the spinal cord. Affinity labeling followed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis revealed distinct molecular sizes of the specific binding sites among the tissues; 70K for the spinal cord, 70K and 90K for the coronary arteries, and 70K and 120K for the atria. These results indicate that the molecular characteristics of the specific binding sites of CGRP in the cardiovascular system are distinct from those in the central nervous system.

Studies on Metabolism of Trazodone, I. Metabolic Fate of [14C]Trazodone Hydrochloride in Rats

Abstract1. One of the main metabolites of [14C]trazodone hydrochloride by rat liver in vitro is hydroxylated trazodone.2. [14C]Trazodone HCI is absorbed very rapidly and the blood level of radioactivity attains a maximum within 15 min after oral administration of 4 mg/kg to rats and thereafter decreases rapidly.3. Urinary and faecal excretions of radioactivity are 49.0 and 46.1% of the dose respectively, during the first 7 days after ingestion, and biliary excretion is 80.0% in 8 h.4. After oral administration of [14C]trazodone HCI to rats the main metabolites in urine and bile are hydroxylated trazodone, β-{3-oxo-s-triazolo[4,3a]-pyridin-2-yl}-propionic acid and their glucuronides.5. Unchanged and hydroxylated trazodone alone are present in brain of rats after oral administration (20 mg/kg); both compounds in brain decrease with similar half-lives to those in plasma.

A simple assay for measurement of urinary p-aminobenzoic acid in the oral pancreatic function test

Abstract A simple method for the measurement of p -aminobenzoic acid (PABA) in urine following oral administration of N -benzoyl- l -tyrosyl- p -aminobenzoic acid (Bz-ty-PABA), a synthetic peptide used for the assessment of exocrine pancreatic function, was investigated using p -dimethylamino cinnamaldehyde (DACA) as a chromogenic reagent. DACA reacted with PABA in acidic solution and the red dye which developed had an absorption spectrum with maximum at 550 nm. Urine containing PABA and its conjugated metabolites was hydrolyzed with HCl, DACA solution was added to a portion of the hydrolysate, and the color intensity was determined. When Bz-ty-PABA was administered orally to healthy humans and patients with pancreatic insufficiency, urinary PABA content determined by the DACA method was in good agreement with that by the diazo-coupling method. This DACA method is preferable to the diazo-coupling method with respect to the simplicity and rapidity of the procedure and to the stability of the reagent solution. It is especially useful for the above application in the clinical laboratory.

Solubilization and Characterization of Calcitonin Gene‐Related Peptide Binding Site from Porcine Spinal Cord

The binding site for calcitonin gene‐related peptide (CGRP) was solubilized with 3‐[(3‐cholamidopropyl) dimethylammonio]‐1‐propane sulfonate (CHAPS) in an active form from porcine spinal cord. l25I‐labeled human α‐CGRP (125I‐CGRP) binding to the solubilized protein was determined by filration using a GF/B glass filter. The maximal binding activity (˜60% of the crude membrane fraction) was obtained with 5 mM CHAPS. 125I‐CGRP binding to the solubilized protein was of high affinity, saturability, and high specificity, having KD and Bmax values of 3.69 pM and 338 fmol/mg of protein, respectively. The binding activity was eluted in a single peak with a molecular mass of 400,000 daltons by gel filtration on TSK gel G4000SW. These results suggest that the solubilized protein may be responsible for the specific binding site.

Studies on Metabolism of Trazodone. III. Species Differences

1. After oral administration of (14C) trazodone HCl (4 mg/kg) to rabbits, the blood level of radioactivity shows a peak at 3 h; unchanged trazodone concentration in brain is higher than that in plasma at 3 h after dosage. 29 The metabolic fate of trazodone in rabbits is different from that in rats and a new, basic metabolite is present in rabbit liver, brain, plasma and urine. 3. The concentration pattern in blood of humans given a single dosage (50 mg) of trazodone HCl is similar to that in rabbits rather than that in rats. 4. The rate of metabolism of trazodone by liver microsomes from mice is approximately 1-5 times higher than that with rat or rabbit liver microsomes.

Metabolic fate of indometacin farnesil, a prodrug of indomethacin : characteristic biotransformation of indometacin farnesil in rats

1. Hydrolysis of indometacin farnesil (IMF), a farnesyl ester of indomethacin, was higher in plasma and pancreatic juice than in liver and kidney homogenates of rats. Plasma hydrolytic activity was extremely low in beagle dog, monkey and human. 2. Orally administered 14C-IMF was absorbed mainly via the throacic lymph duct and distributed into tissues such as liver, adrenal and spleen as the unchanged from; the 14C in rat plasma was present mainly as indomethacin released from IMF. 3. The concentration ratios of indomethacin in carrageenin-induced inflamed paw to blood after 14C-IMF administration were significantly greater than those after 14C-indomethacin dosing. 4. These results indicate that absorbed IMF might be transported as the unchanged drug into tissues, including the site of inflammation and then hydrolysed to indomethacin in the tissues.

Studies on Metabolism of Trazodone, II. Metabolic Fate after Intravenous Administration and Effects on Liver Microsomal Drug-Metabolizing Enzymes in Rats

1. The blood level of radioactivity following intravenous injection of [14C]-trazodone hydrochloride (4 mg/kg) decreases with three half-lives of 4.4 min, 49 min and 9.0 h.2. The urinary and faecal excretions of radioactivity and the pattern of urinary and biliary metabolites after injection are approximately similar to those after oral administration.3. A major metabolite of trazodone in rat bile and urine is the glucuronide conjugate of trazodone hydroxylated at C4 of benzene ring.4. The concentration of unchanged trazodone in rat brain is higher than that in plasma.5. Trazodone HCl (80 mg/kg) administered intraperitoneally twice daily for 7 days to rats had no effect on liver weight, microsomal protein content, cyto-chrome P-450 content or on the metabolism of [14C]trazodone HCl and other substrates such as imipramine and aniline.