Mitochondrial gene mutations in the tRNA(Leu(UUR)) region and diabetes: prevalence and clinical phenotypes in Japan

BACKGROUND

Mitochondrial gene mutations play a role in the development of diabetes mellitus. We have assessed the frequency of the A3243G and other mitochondrial mutations in Japan and in the relationship to clinical features of diabetes.

METHODS

DNA was obtained from peripheral leukocytes of 240 patients with diabetes mellitus (39 with type 1; 188 with type 2; 13 with gestational diabetes) and 125 control subjects. We used PCR-restriction fragment length polymorphism analysis (ApaI) for A3243G and PCR-single-strand conformation polymorphism analysis to determine the mutations in the mitochondrial gene including nucleotide position 3243.

RESULTS

The A3243G mutation was found in seven patients, and an inverse relationship was observed between the degree of heteroplasmy and the age at onset of diabetes. A3156G, G3357A, C3375A, and T3394C were detected in addition. Those who shared the same mutation showed similar clinical characteristics, thus representing a putative clinical subtype. The patients with A3156G had a sudden onset of hyperglycemia and showed a rapid progression to an insulin-dependent state with positive anti-glutamic acid decarboxylase antibody. Those with T3394C showed a mild defect in glucose-stimulated insulin secretion, and hyperglycemia appeared after adding such factors as aging or obesity.

CONCLUSIONS

The identification of mitochondrial gene mutations allows preclinical diagnosis of diabetes and prediction of the age at onset by evaluating the degree of heteroplasmy in cases with A3243G. Mutation detection may also be important for patient management and identification of affected family members.

Kinetic analysis of the disposition of insulin-like growth factor 1 in healthy volunteers

PURPOSE

Insulin-like growth factor 1 (IGF-1) is predominantly bound to its specific binding proteins (IGFBPs) in circulating plasma. In the present study, pharmacokinetic analysis of IGF-1 was performed in healthy volunteers to characterize the effect of interactions with IGFBPs on IGF-1 disposition.

METHODS

Plasma concentration profiles of both free and bound IGF-1 were examined at several doses. An in vitro plasma protein binding was also analyzed.

RESULTS

The total body clearance (CLtotal) for the free IGF-1 was much higher than the creatinine clearance, suggesting that the major elimination pathway is by a route other than renal glomerular filtration. The CLtotal for the free IGF-1 exhibited a dose-dependent reduction whereas that for the sum of unbound and bound IGF-1 increased on increasing the dose. The data obtained fitted closely a one-compartment model that involved the binding and dissociation of IGF-1, as well as its biosynthesis and elimination. The estimated parameters suggest that IGF-1 exhibits high affinity binding to IGFBPs. the rate-limiting step in the overall elimination being the dissociation from IGFBPs.

CONCLUSIONS

The saturation of both the plasma protein binding and elimination accounts for the nonlinear pharmacokinetic profile. The binding to IGFBPs markedly limits both the distribution and elimination of IGF-1.

Pharmacodynamic effects and kinetic disposition of rabeprazole in relation to CYP2C19 genotypes

BACKGROUND

S-mephenytoin 4'-hydroxylase (CYP2C19) catalyses the metabolism of rabeprazole to some extent. Based on the metabolic and pharmacokinetic differences among other proton pump inhibitors such as omeprazole, lansoprazole and pantoprazole, rabeprazole appears to be the least affected proton pump inhibitor by the CYP2C19-related genetic polymorphism.

AIM

To determine whether the pharmacodynamic effects of rabeprazole on intragastric pH and serum gastrin levels, and its pharmacokinetics depend on the CYP2C19 genotype status.

METHODS

Eighteen healthy subjects, whose CYP2C19 genotype status was previously determined, participated in the study. They consisted of six each of homozygous extensive metabolisers (homo EMs), heterozygous extensive metabolisers (hetero EMs), and poor metabolisers (PMs). Helicobacter pylori status was determined by serology. After a single oral dose of 10 mg or 20 mg rabeprazole or water only (baseline data), intragastric pH values were monitored for 24 h. Plasma levels of rabeprazole and serum gastrin were also measured for 24 h post-dose.

RESULTS

Five homo EM, six hetero EM and four PM subjects were H. pylori-negative. After rabeprazole administration, significant differences in intragastric mean pH values, serum gastrin AUC(0-24) and plasma levels of rabeprazole were observed among the three different genotype groups.

CONCLUSION

The pharmacodynamic effects of rabeprazole and its pharmacokinetics depend on the CYP2C19 genotype status.

P-hydroxylation of phenobarbital: relationship to (S)-mephenytoin hydroxylation (CYP2C19) polymorphism

The aim of the current study was to compare the pharmacokinetics of phenobarbital (PB) in extensive metabolizers (EMs) and poor metabolizers (PMs) of S-mephenytoin. Ten healthy volunteers (5 EMs and 5 PMs) were given 30 mg PB daily for 14 days. PB and p-hydroxyphenobarbital (p-OHPB) in serum and urine were measured by high-performance liquid chromatography (HPLC). Urinary excretion (12.5% versus 7.7%) and formation clearance (29.8 versus 21.1 mL/h) of p-OHPB, one of the main metabolites of PB, were significantly lower (p < .05) in PMs than in EMs. However, area under the serum concentration-time curve (153.3 in the EMs versus 122.9 microg x h/mL in the PMs), total (210.8 versus 254.9 mL/h) and renal clearance (53.1 versus 66.1 mL/h) of PB were identical between the two groups. To compare the inducibility of CYP2C19, mephenytoin was also given prior to and on the last day of PB treatment. The urinary level of 4'-hydroxymephenytoin was analyzed by a validated gas chromatograpy/mass spectrometry (GC/MS) method. The mephenytoin hydroxylation index did not change in either EMs (1.42 versus 1.42) or PMs (341.4 versus 403.5), showing that CYP2C19 was not induced by treatment with PB. These results indicated that the p-hydroxylation pathway of PB co-segregates with the CYP2C19 metabolic polymorphism. However, the overall disposition kinetics of PB were not different between EMs and PMs, and therefore polymorphic CYP2C19 seems have no major clinical implications.

Pharmacokinetics and pharmacodynamics of insulin aspart, a rapid-acting analog of human insulin, in healthy Japanese volunteers

Pharmacokinetic and pharmacodynamic properties of a rapid-acting analog of human insulin, insulin aspart, were compared with those of soluble human insulin in Japanese healthy subjects. Subcutaneous single injections (0.025 and 0.05 U/kg body weight (BW)) of insulin aspart produced a significantly earlier peak of exogenous insulin level in comparison with human insulin (30.8+/-13.8 versus 61.3+/-14. 6 min, P<0.9001 for 0.025 U/kg; and 39.2+/-18.8 versus 99.2+/-53.8 min, P<0.005 for 0.05 U/kg). The peak serum level of insulin aspart was higher than that of human insulin (23.0+/-6.0 versus 9.9+/-3.1 microU/ml for 0.025 U/kg; and 30.9+/-9.2 versus 13.3+/-4.1 microU/ml for 0.05 U/kg, P<0.0001). The time to the minimal level of glucose after insulin aspart was significantly shorter compared with human insulin (P<0.05 for 0.025 U/kg BW and P<0.01 for 0.05 U/kg BW). The Delta change in blood glucose induced by insulin aspart was larger than that observed for human insulin at any dose (P<0.001). The repeated injection of insulin aspart before each meal also resulted in a rapid rise in exogenous insulin level with peak level obtained approximately 40 min after insulin aspart at any dose. When compared with results of other trials with insulin aspart, the present results showed that pharmacokinetic and pharmacodynamic profiles of the rapid-acting analog insulin aspart in Japanese subjects are no different from those in nonJapanese subjects.

Lack of differences in diclofenac (a substrate for CYP2C9) pharmacokinetics in healthy volunteers with respect to the single CYP2C9*3 allele

OBJECTIVES

Evidence exists to suggest that diclofenac is metabolised by CYP2C9. The present study was undertaken in order to evaluate the effect of the single CYP2C9*3 variant on drug metabolism using diclofenac as a probe drug.

METHODS

A single dose of diclofenac was administered orally to 12 healthy subjects in whom the genotype of CYP2C9 had been determined previously. The disposition kinetics of diclofenac were compared between homozygotes for the wild type (CYP2C9*1/*1, n = 6) and heterozygotes for the Leu359 variant (CYP2C9*1/*3, n = 6).

RESULTS

For diclofenac, the following kinetic parameters were observed in the CYP2C9*1/*1 and CYP2C9*1/*3 subjects, respectively (mean +/- SD): apparent oral clearance (ml/kg/h) 355.8 +/- 56.9 and 484.4 +/- 155.3; area under plasma concentration time curve (microg h/ml) 2.7 +/- 0.7 and 1.9 +/- 0.6. The formation clearance of 4'-hydroxydiclofenac (ml/kg/h) was 63.6 +/- 19.1 in the CYP2C9*1/*1 subjects compared with 75.9 +/- 27.6 in the CYP2C9*1/*3 subjects. There were no significant differences in any of the kinetic parameters for either diclofenac disposition or formation clearance of 4'-hydroxydiclofenac between the two genotype groups.

CONCLUSION

Since the disposition kinetics of diclofenac does not change in subjects with the single CYP2C9*3 mutant allele, it is suggested that the effects of CYP2C9 polymorphisms on the drug metabolism tend to be substrate specific.

Effect of cimetidine and probenecid on pilsicainide renal clearance in humans

OBJECTIVE

To investigate the effect of cimetidine and probenecid on the renal clearance of pilsicainide in healthy subjects.

METHODS

Nine healthy men (age range, 21 to 38 years) were given oral doses of 50 mg pilsicainide hydrochloride alone, with coadministration of 800 mg oral cimetidine, or with coadministration of 1,500 mg oral probenecid on three occasions in a Latin-square order. Urine and venous blood samples were collected on a timely basis. The concentration of pilsicainide in plasma and urine were determined by an HPLC method.

RESULTS

Concomitant administration of cimetidine significantly increased the area under the plasma concentration-time curve of pilsicainide by a mean of 33%, prolonged elimination half-life by a mean of 24% (from 5 to 6.2 hours), reduced apparent oral clearance by a mean of 26% (from 14.7 +/- 0.1 to 10.8 +/- 0.8 L/h) and reduced renal clearance by a mean of 28% (from 196.8 +/- 53.9 to 141.8 +/- 25.9 mL/min). The net renal clearance by tubular secretion was significantly reduced by a mean value of 38%, from 151.4 +/- 62.9 to 93.0 +/- 31.1 mL/min. Coadministration of probenecid did not show any changes in plasma concentrations of pilsicainide, pharmacokinetics, or the net renal clearance by tubular secretion of pilsicainide.

CONCLUSIONS

Pilsicainide appeared to be secreted by the active transport system for organic bases in the proximal tubule, and the excretion of pilsicainide was inhibited by cimetidine.

Relationship between time after intake of grapefruit juice and the effect on pharmacokinetics and pharmacodynamics of nisoldipine in healthy subjects

A clinical study was performed in eight healthy volunteers to investigate the effect of various timing of grapefruit juice intake on nisoldipine pharmacokinetics and pharmacodynamics, and to validate our pharmacokinetic model. The subjects were given 10 mg oral nisoldipine with water (control), or 5 mg oral nisoldipine with 200 mL grapefruit juice (G0) or with water at 14 (G14), 38 (G38), 72 (G72) or 96 hours (G96) after a 7-day period of thrice-daily intake of grapefruit juice. Grapefruit juice ingestion did not affect heart rate or the effect area during the first 8 hours of heart rate after nisoldipine administration, although significant decreases of systolic and diastolic blood pressure were caused in G0 by coadministration of grapefruit juice with nisoldipine. Headaches were reported by 3, 2, and 1 persons in G0, G14, and G38, respectively, but no subjects in G72 and G96 reported headaches. Compared with the control group, the maximum plasma concentration of nisoldipine was significantly increased after grapefruit juice intake in G0 and G14, and the plasma concentration was significantly increased at each time in G0 to G72. Therefore the effect of grapefruit juice decreased time dependently and lasted for at least 3 days after intake. Furthermore, our model gave predicted values in good agreement with the observed values. It is therefore necessary to withhold grapefruit juice for at least 3 days before administration of the drug to prevent grapefruit juice-nisoldipine interaction.

Pharmacokinetic analysis of felodipine-grapefruit juice interaction based on an irreversible enzyme inhibition model

Aims Ingestion of grapefruit juice (GFJ) alters the pharmacokinetics of various orally administered drugs. Quantitative evaluation of this GFJ-drug interaction is required for the proper clinical management of patients. Methods Using felodipine as a model drug, we constructed a pharmacokinetic model based on irreversible inhibition of intestinal cytochrome P450 3A4 (CYP3A4) by GFJ. We fitted previously published data [5, 6] for felodipine ER (extended release formulation) to the ratio of CLGI,int before and after grapefruit juice ingestion by nonlinear least-squares regression analysis to estimate the reaction rate constant between GFJ and CYP3A4 (K) and the elimination rate constant of CYP3A4 (k ).

RESULTS

The model gave a turnover rate of CYP3A4 of 0.0849 h-1, corresponding to a half-life of 8.16 h, in agreement with reported values. The AUC-time profiles of felodipine ER in the case of different amounts and schedules of GFJ ingestion were simulated using the parameter values estimated from the model.

CONCLUSIONS

The modelling leads to the important conclusion that GFJ-felodipine interaction increases with increasing frequency and amount of GFJ ingestion, and that an interval of 2-3 days between GFJ intake and felodipine administration is necessary if GFJ-felodipine interaction is to be avoided.

Cerebral acetylcholine levels and long-term spatial cognitive impairment following middle cerebral artery occlusion in rats

The behavioral and neurochemical changes in the chronic phase of permanent occlusion of the right middle cerebral artery (MCA) in rats were investigated. Nineteen MCA-occluded rats failed to solve the 8-arm radial maze task (cognitively impaired rats), while 11 MCA-occluded rats could complete it (cognitively unimpaired rats). When a delay of 60 min was imposed in the task, however, 5 cognitively unimpaired rats failed to complete the task. The rats that underwent behavioral testing were studied for any changes in ACh levels in various brain regions using HPLC with electrochemical detection. The ACh levels in the infarcted areas decreased considerably in all MCA-occluded rats, but no region of the infarcted areas correlated with the spatial cognitive deficit. The ACh levels tended to decrease in the frontal cortex of the cognitively impaired rats and greatly increased in both ipsilateral and contralateral parietal cortex of the cognitively unimpaired rats. A significant correlation was observed between the ACh levels and spatial cognitive deficit in the contralateral frontal cortex, and ipsilateral and contralateral parietal cortex. These results suggest that the cholinergic function of the frontal and parietal cortices might play a role in acquiring spatial cognition in MCA-occluded rats.

Reliability of the omeprazole hydroxylation index for CYP2C19 phenotyping: possible effect of age, liver disease and length of therapy

AIMS

To evaluate the reliability of the omeprazole hydroxylation index as a marker for polymorphic CYP2C19 activity in a Japanese population of healthy young subjects (n = 78) and patients with peptic ulcer (n = 72).

METHODS

Healthy subjects were administered a single dose of omeprazole (20 mg), whereas patients received 20 mg daily for at least 1 week. The ratio of the serum concentration of omeprazole to hydroxyomeprazole at 3 h postdose was determined and used as a measure of CYP2C19 activity. The CYP2C19 wild type (wt) gene and four mutant alleles associated with the poor metaboliser phenotype of (S)-mephenytoin, CYP2C19*2 in exon 5, CYP2C19*3 in exon 4, CYP2C19m4 in exon 9, and CYP2C19m3 in the initial codon were analysed.

RESULTS

In the healthy volunteer study there was complete concordance between genotype and phenotype. However, eight of the patients who had the EM genotype had a high value for their hydroxylation index, and were classified as phenotypic PMs. No CYP2C19m4 and CYP2C19m3 mutations were detected in the eight mismatched patients. They were all genotypic heterozygous EMs, elderly (> or = 65 years) and/or had hepatic disease. Therefore, impaired CYP2C19 activity combined with partial saturation of omeprazole metabolism during multiple dosing may have contributed to the discrepancy between CYP2C19 genotyping and phenotyping.

CONCLUSION

Although omeprazole has been used instead of mephenytoin as a probe for polymorphic CYP2C19, it does not appear to be reliable enough for clinical application in Japanese patients.

Role of nitric oxide in isoprenaline and sodium nitroprusside-induced relaxation in human hand veins

AIMS

Recent reports, largely in animal models, have suggested that either inhibition of nitric oxide (NO) synthase or endothelium removal in arteries inhibits the response to isoprenaline, a beta-adrenoceptor agonist, and also enhances the response to sodium nitroprusside, a nitrovasodilator. This in vivo study was designed to determine whether N(G)-monomethyl-L-arginine (L-NMMA), an inhibitor of NO synthesis, influences relaxation of human hand veins mediated by isoprenaline or by sodium nitroprusside.

METHODS

Using the dorsal hand vein technique, full dose-response curves to bradykinin (0.27-278 ng min(-1), n=6), isoprenaline (2.12-271 ngmin(-1), n=8) and sodium nitroprusside (0.01-634 ng min(-1) n=7) were generated on separate occasions before and after L-NMMA co-infusion (50 microg min(-1)).

RESULTS

In veins preconstricted with the alpha1-adrenoceptor-selective agonist phenylephrine, the three vasodilators induced maximal responses (Emax) of 119+/-35, 72+/-18 and 103+/-17%, respectively. L-NMMA inhibited relaxation to bradykinin by 64% (P=0.014) but did not influence relaxation induced by isoprenaline. The sensitivity to sodium nitroprusside was significantly enhanced by L-NMMA co-infusion (concentration shift of 2.3, P=0.031). CONCLUSIONS; We conclude that in human veins, spontaneously released NO does not play a major role in isoprenaline-induced relaxation. Our results also suggest that the effects of sodium nitroprusside in this vascular bed may be attenuated by endothelium-derived NO.

Inhibition of angiotensin-converting enzyme in human hand veins

Conversion of angiotensin I to angiotensin II likely occurs in human veins, supporting the existence of endothelial angiotensin-converting enzyme (ACE) activity in these vessels. Using the dorsal hand vein technique, we investigated the effects of 2 ACE inhibitors, captopril (single oral dose of 6.25 mg) and enalaprilat (local infusion of 1 microgram/min), on venous responsiveness in healthy subjects. Orally administered captopril induced a marked decrease in angiotensin I- but not angiotensin II-induced venoconstriction. This blunted response persisted for at least 4 hours. Enalaprilat and captopril increased the sensitivity to bradykinin, decreasing the dose producing half-maximal response (ED50) of bradykinin 18-fold and 5-fold, respectively, without changing the maximal venodilatory response. These results confirm that there is substantial rapid metabolism of angiotensin I in human veins and suggest that a single dose of locally infused angiotensin I can be used with the dorsal hand vein technique to assess the time-course effect of vascular ACE inhibition after oral administration. Our findings also extend previous in vitro observations in human veins by showing that these agents potentiate the venodilatory effects of bradykinin in vivo.

Endothelial dysfunction in human hand veins is rapidly reversible after smoking cessation

Cigarette smoking has been shown to impair endothelium-dependent dilation in arteries. We tested the hypothesis that cigarette smoking also impairs endothelium-dependent venodilation and evaluated changes in this response after smoking cessation in a time-course study using the dorsal hand vein technique. Dose-response curves were constructed in smokers and nonsmokers by infusing bradykinin (1-278 ng/min), an endothelium-dependent vasodilator, and nitroglycerin (0.006-1,583 ng/min), an endothelium-independent vasodilator, into hand veins preconstricted with the selective alpha1-adrenergic agonist phenylephrine. The maximal venodilation induced by bradykinin was 89 +/- 5% in controls (n = 16) and 61 +/- 7% in smokers (n = 18; P = 0.02). No difference in nitroglycerin-induced venodilation was observed between the two groups. Coinfusion of L-arginine (0.33 mg/min) markedly improved the bradykinin-induced venodilation in smokers (52 +/- 7 to 90 +/- 9%; P < 0.01). After acute smoking cessation (n = 7), restoration to normal bradykinin-induced venodilation was observed within 24 h, whereas no change in the response to a maximally effective dose of nitroglycerin (1,583 ng/min) was detected. In a human vein model appropriate for testing vascular functional alterations, this study demonstrates that smoking impairs endothelium-dependent venodilation in heavy smokers. Moreover, this endothelial dysfunction appears to be rapidly reversible after smoking cessation. This model may be useful in studies evaluating mechanisms of endothelial dysfunction and interventions to modify it.

Genetic polymorphism of cytochrome P450s, CYP2C19, and CYP2C9 in a Japanese population

Genotypings of two mutations (*2 and *3) in CYP2C19 and the amino acid variants (Arg144/Cys, Tyr358/Cys, Ile359/Leu, and Gly417/Asp) in CYP2C9 were carried out in 140 unrelated Japanese subjects. Thirty-three subjects (23.6%) were genotypically identified as poor metabolizers of CYP2C19, and the allele frequencies of the CYP2C19*2 and CYP2C19*3 were 0.35 and 0.11, respectively. The authors' findings are in agreement with the 18% to 23% prevalence of poor metabolizers in the Japanese populations previously phenotyped. In CYP2C9, all subjects were homozygous (CYP2C9*1) for Arg144, Tyr358, Ile359, and Gly417, except for five subjects (3.6%) who were heterozygous for the Leu359 (CYP2C9*3). The frequencies of Arg144, Tyr358, Ile359, Leu359, and Gly417 variants were 1.0, 1.0, 0.982, 0.018, and 1.0, respectively. The low frequency of the Cys144 allele (CYP2C9*2) in the Japanese population is different from the frequency recently found in British subjects (allele frequency, 0.125 to 0.192). The results suggest that the known interindividual variations in the CYP2C9 sequence among Japanese subjects is small, and that Ile359/Leu is one possible site showing interracial polymorphism.

Stereoselective 4'-hydroxylation of phenytoin: relationship to (S)-mephenytoin polymorphism in Japanese

AIMS

The aim of this study was to clarify whether phenytoin (PHT) stereoselective hydroxylation cosegregates with (S)-mephenytoin phenotype.

METHODS

A single dose of PHT (100 mg) was administered orally to six healthy Japanese subjects in whom the genotype and phenotype of CYP2C19 had been determined previously. The urinary excretion profiles of the metabolites of PHT, (R)- and (S)-p-HPPH [5-(4-hydroxyphenyl)-5-phenylhydantoin] up to 361 postdose were compared between the two groups of poor metabolizers (PMs, n = 3) and extensive metabolizers (EMs, n = 3) with respect to CYP2C19. CYP2C9 genotype was also determined.

RESULTS

All the alleles were found to be wild type (Arg144 Tyr358Ile359Gly417) in each subject. The mean value for cumulative urinary excretion of unchanged PHT was not significantly different between the PMs and the EMs. However, recovery of (R)-p-HPPH at 36 h was 3.5-fold lower and that of (S)-p-HPPH 1.3-fold lower in PMs than in EMs. Although the mean urinary excretion values for both metabolites were significantly lower in the PMs than in the EMs, the difference between the two groups was larger for (R)-p-HPPH. A significant negative correlation was observed between the hydroxylation index of omeprazole (the ratio between the serum concentrations of omeprazole and hydroxyomeprazole in blood samples drawn 3 h after drug intake) and the log10 0-12 h urinary recovery of (R)-p-HPPH.

CONCLUSIONS

In humans, the 4'-hydroxylation of PHT is highly stereoselective towards formation of the (S)-enantiomer. Thus, (S)-hydroxylation by CYP2C9 might be the major determinant of the disposition of PHT. However, these results support the hypothesis that the stereoselective hydroxylation pathway of PHT to form (R)-p-HPPH cosegregates with the CYP2C19 metabolic polymorphism.

No effect of high-protein food on the stereoselective bioavailability and pharmacokinetics of verapamil

The effects of high-protein food on the bioavailability of both the racemate and individual enantiomers of verapamil were investigated in 12 healthy volunteers using a randomized crossover design. Food had no effect on any parameter of bioavailability for both the racemate and the individual enantiomers of verapamil except time to maximum concentration (tmax), which was significantly prolonged after food intake. The pharmacokinetics of the enantiomers of norverapamil were not significantly changed by food intake. These results suggest that high-protein food does not alter the pharmacokinetics and bioavailability of either the racemate or the individual enantiomers of verapamil. Therefore, the clinical efficacy of verapamil is not related to food intake, except for a slight prolongation in the time to onset of the pharmacologic effects. The present data can be applied to the high-protein content meal intake.

Pharmacokinetics of omeprazole (a substrate of CYP2C19) and comparison with two mutant alleles, C gamma P2C19m1 in exon 5 and C gamma P2C19m2 in exon 4, in Japanese subjects

The pharmacokinetic profile of omeprazole was examined in 27 healthy Japanese volunteers, and the results were analyzed in relation to genotype for the two mutations, CgammaP2C19m1 in exon 5 and CgammaP2C19m2 in exon 4, associated with the poor metabolizer phenotype. Of the 27 individuals analyzed, 10 were homozygous for the wild-type (wt) allele in both exon 5 and exon 4 (wt/wt; 37.0%, pattern GI), five were heterozygous for the CgammaP2C19m1 (wt/m1; 18.5%, G2), five were heterozygous for the CgammaP2C19m2 (wt/m2; 18.5%, G3), two were heterozygous for the two defects (m1/m2; 7.4%, G4), and five were homozygous for the CgammaP2C19m1 (m1/m1; 18.5%, G5). The allele frequencies of the m1 and m2 mutation were 0.31 and 0.13, respectively. A correlation between the rate of metabolism of omeprazole and genotype was observed. The mean clearance values of omeprazole in patterns G1, G2, G3, G4, and G5 were 1369.0, 332.7, 359.0, 70.8, and 89.5 ml/hr/kg, respectively. The relative area under the serum concentration-time curve (AUC) ratio of omeprazole to 5-hydroxyomeprazole in patterns G1, G2, G3, G4, and G5 was 1:2.8:3.4:16:17.2. A similar relation was observed in the omeprazole/5-hydroxyomeprazole serum concentration ratio, determined 3 hours after drug intake (1:3:4:18.8:20.3). There were significant (p < 0.05 to 0.01) differences in the disposition kinetics of omeprazole between the subjects with patterns G1, G2, and G3 and the subjects with patterns G4 and G5. The results indicate that the 5-hydroxylation pathway of omeprazole is clearly impaired in subjects with m1/m2 and m1/m1.

Long-term spatial cognitive impairment after middle cerebral artery occlusion in rats: no involvement of the hippocampus

The behavioral and neurochemical changes in the chronic phase of permanent occlusion of the right middle cerebral artery (MCA) in rats were investigated. One month after MCA occlusion, 23 rats were unable to solve a radial eight-arm maze task during an entire 1-month period, whereas seven rats were able to solve this task. Three months after occlusion, 19 MCA-occluded rats failed to solve the task successfully again for at least 1 month (the cognitively impaired rats), whereas 11 MCA-occluded rats were able to solve it (the cognitively unimpaired rats). The rats that underwent behavioral testing were examined for any changes in the acetylcholine (ACh) levels in the hippocampus using HPLC with electrochemical detection or the formation of long-term potentiation (LTP) in the population spike of the hippocampal CA1 field. The immunohistochemical distribution of either the microtubule-associated protein 2 (MAP2) or glial fibrillary acidic protein (GFAP) in the hippocampus of the cognitively impaired rats was also studied. In the cognitively impaired rats, neither the suppression of the induction of LTP, nor the degradation of MAP2, nor the increase in the GFAP immunoreactivity was observed in the hippocampus. The levels of ACh in the hippocampus did not change significantly among the cognitively impaired, unimpaired, and the sham-operated rats. These results suggest that MCA occlusion is capable of producing long-term spatial cognitive disturbance in rats without any evidence of neurobiological damage in the hippocampus.

Long-term spatial cognitive impairment following middle cerebral artery occlusion in rats. A behavioral study

Behavioral changes in the chronic phase of permanent occlusion of the right middle cerebral artery (MCA) in rats were investigated. One month after MCA occlusion, 23 rats were unable and 7 rats were able to solve a radial 8-arm maze task during a 1-month period. Three months after occlusion, 19 MCA-occluded rats failed to solve the task successfully again during at least a 1-month period (the cognitively impaired rats), and 11 MCA-occluded rats were able to solve it (the cognitively unimpaired rats). When a delay of 60 min was imposed for this task, five cognitively unimpaired rats failed to solve it. The locomotor activity of the cognitively impaired rats increased significantly 2 months after occlusion, and this increase showed good correlation with spatial cognitive deficit. However, the mean time a rat spent at each arm remained unchanged among the cognitively impaired, unimpaired, and sham-operated rats. There was no significant difference in the ratio between the cognitively impaired and unimpaired rats for disturbed motor coordination. These results suggest that MCA occlusion is capable of producing long-term spatial cognitive disturbance in rats. In addition, this spatial cognitive deficit does not seem to be primarily due to hypermotility or a disturbance in motor coordination.

Effects of the N-methyl-D-aspartate antagonists on the rise in [Ca2+]i following depolarization in aged rat brain synaptosomes

The effects of non-competitive NMDA antagonists, MK-801 and dextrorphan in relation to the rise in intracellular Ca2+ concentrations ([Ca2+]i) after stimulation with 15 mM K+ in whole brain synaptosomes from young (3 months old) and aged (24 months old) Fisher344 rats were examined. A fluorescent chelating agent, Rhod-2, was employed to monitor any alterations of K(+)-evoked [Ca2+]i. In young rats, the rise in [Ca2+]i following depolarization was affected by neither dextrorphan (1, 10, 100 microM) nor MK-801 (0.1, 1, 10 microM), while in aged rats, 1 microM dextrorphan and 0.1 microM MK-801 brought about a significant increase in [Ca2+]i following depolarization. In low Mg2+ medium, 10 microM MK-801 and 100 microM dextrorphan significantly inhibited the rise in [Ca2+]i after stimulation with 15 mM K+ in young rats, while neither dextrorphan nor MK-801 could affect the rise in [Ca2+]i significantly in aged rats. When 100 microM NMDA was applied in a medium containing 1.2 mM Mg2+, the rise in [Ca2+]i following depolarization was slightly inhibited by 1 microM MK-801 in young rats, but it was not inhibited significantly by dextrorphan. In aged rats, both 100 microM dextrorphan and 10 microM MK-801 strongly inhibited the rise in [Ca2+]i following depolarization in the presence of 100 microM NMDA. Instead of NMDA, when 100 microM alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), a non-NMDA receptor agonist, was applied, dextrorphan did not inhibit the rise in [Ca2+]i. In low Mg2+ medium, 100 microM NMDA potentiated the inhibitory effect of 10 microM dextrorphan in young rats, while 100 microM dextrorphan or MK-801 did not show any further inhibition by adding 100 microM NMDA. The addition of 100 microM AMPA did not affect the effect of dextrorphan in a low Mg2+ medium in young rats. These results suggest that NMDA antagonist-mediated [Ca2+]i homeostatic system may alter through aging. In addition, the findings that NMDA potentiated the inhibitory effect of NMDA antagonist, which being further potentiated by aging or lowered extrasynaptosomal Mg2+, indicate the possibility that the Mg2+ block to NMDA receptors might be attenuated through aging.

The facilitating and suppressing effects of delta 9-tetrahydrocannabinol on the rise in intrasynaptosomal Ca2+ concentration in rats

The effects of delta 9-tetrahydrocannabinol (delta 9-THC) on the rise in intracellular Ca2+ concentrations ([Ca2+]i) after stimulation with 15 mM or 29 mM K+ in rat whole brain synaptosomes were examined. A fluorescent chelating agent, Rhod-2, was employed to monitor any alterations of K(+)-evoked [Ca2+]i. Pretreatment with 10(-10) M delta 9-THC for 3 min enhanced K(+)-evoked [Ca2+]i significantly, while 10(-9), 10(-8) or 5 x 10(-8) M delta 9-THC significantly inhibited the K(+)-evoked [Ca2+]i. These results suggest that delta 9-THC had a biphasic effect on the K(+)-evoked Ca2+ response in rat brain synaptosomes.