Expression of gap junction protein connexin 32 in chronic liver diseases

BACKGROUND

Gap junctions contain intercellular channels through which contacting cells communicate directly. The expression of connexin 32, a major gap junction protein in the liver, during the progression of chronic liver diseases has not yet been clarified.

METHODS

Immunohistochemical staining was performed using anti-connexin 32 antibody on 6 specimens of normal human liver, 7 of chronic viral hepatitis, and 7 of liver cirrhosis.

RESULTS

The number of gap junction plaques in chronic viral hepatitis and liver cirrhosis was significantly smaller than that in normal liver (10350+/-2180 and 7550+/-3040 vs 22560+/-3700 spots/mm2, p<0.01). The number of gap junction plaques tended to be lower in liver cirrhosis than in chronic viral hepatitis.

CONCLUSION

These results suggest that in chronic liver diseases impaired intercellular communication between hepatocytes occurs.

Expression of galectin-1 mRNA correlates with the malignant potential of human gliomas and expression of antisense galectin-1 inhibits the growth of 9 glioma cells

Although its precise function has not yet been established, galectin-1 seems to play a role in tumor progression. In this study, we investigated galectin-1 mRNA expression in human glioma specimens and glioma cell lines. Northern blot analysis showed higher galectin-1 mRNA levels in glioma tissues. The 0.7-kb galectin-1 mRNA transcript was detected, and the expression level correlated with the malignant state, from low-grade astrocytoma to glioblastoma. In several human glioma specimens, immunohistochemical examination with antiserum against a synthetic peptide corresponding to the predicted C-terminal sequence of the protein showed high levels of galectin-1 expression. To clarify the correlation between the expression of galectin-1 and the malignancy of gliomas, we examined whether expression of antisense galectin-1 would suppress tumor growth in rat 9L cells that express high levels of galectin-1. The cells were transfected with a plasmid DNA that produces antisense galectin-1 mRNA under the control of the metallothionein promoter, and stable clones expressing low levels of galectin-1 protein in comparison with control clones were isolated. Cells with low levels of galectin-1 displayed dramatic phenotypic changes in their morphology and growth properties compared with vector-transfected control 9L cells. Our data suggest that decreased expression of galectin-1 may arrest the growth of rat 9L cells.

Inhibitory effects of post low dose gamma-ray irradiation on ferric-nitrilotriacetate-induced mice liver damage

We studied the effects of a single post whole-body low-dose irradiation (50 cGy of gamma-ray) on mice with ferric nitrilotriacetate (Fe3+-NTA)-induced transient hepatopathy. As a result, low-dose irradiation accelerated the rate of recovery. Based on the changes in glutamic oxaloacetic transaminase (GOT) activities, glutamic pyruvic transaminase (GPT) activities and lipid peroxide levels, it was shown that hepatopathy was improved by low-dose irradiation 3 h after Fe3+-NTA administration. This may be because of the enhancement of antioxidant agents such as total glutathione (GSH + GSSG), glutathione peroxidase (GPX), glutathione reductase (GR) and gamma-glutamylcysteine synthetase (gamma-GCS) by low-dose irradiation. These findings suggest that low-dose irradiation relieved functional disorders at least in the livers of mice with active oxygen species related diseases.

[Validity and reproducibility of a semi-quantitative food frequency questionnaire for nutritional education of patients of diabetes mellitus (FFQW65)]

BACKGROUND

A self-administered semi-quantitative food frequency questionnaire with 65 food lists (FFQW65) was developed for the nutritional education of patients of diabetes mellitus.

METHODS

Relative validity and reproducibility of nutrient intakes as assessed by FFQW65 were investigated in volunteers of 71 males. To assess the relative validity, a one-week diet record was used as a reference. The FFQW65 was administered twice at an interval of 10 month in order to assess the reproducibility. Log transformed data was used to obtain Pearson correlation coefficients.

RESULTS

As for the validity, Pearson correlation coefficient of total energy intake of breakfast was 0.74 and the relative difference between predicted value and diet record was relatively small (the difference was -5 kcal and relative difference rate was 1.1%). Compared with breakfast, those for lunch, supper and one-day total energy intakes were relatively lower (0.52, 0.66 and 0.64, respectively) and the relative differences were around 10%, respectively. The one-day intakes of sixteen nutrients (except for potassium and niacin) ranged from 0.28 to 0.64. Energy adjusted correlation coefficients for protein, iron and cholesterol were low (0.16, 0.14 and 0.19, respectively). Those for the other thirteen nutrients ranged from 0.26 to 0.65. As for the reproducibility, the second survey using FFQW65 was administered to 64 males. Pearson correlation coefficient of one-day total energy intake was 0.76 and those for the other nutrients ranged from 0.54 (vitamin D) to 0.81 (calcium).

CONCLUSION

The results suggest that FFQW65 can be used for the evaluation of energy intake by usual meals for nutrition education of patients of diabetes mellitus.

On site of action of grayanotoxin in domain 4 segment 6 of rat skeletal muscle sodium channel

Grayanotoxin I (GTX I) is a diterpenoid extracted from the family of Ericaceae that binds to Na(+) channels and causes persistent activation. We investigated the interaction of GTX I with the amino acid residues I1575, F1579 and Y1586 in transmembrane segment D4S6 of micro1. In F1579A, GTX shifted the threshold potential about 50 mV in the hyperpolarizing direction and modified Na(+) channels twice as efficiently as that in wild-type. In contrast, these GTX-effects were eliminated completely in the I1575A mutant and were reduced substantially in mutant Y1586A. Lysine substitution for F1579 significantly reduced and for Y1586 completely eradicated the GTX-effect. Our data suggest that the GTX receptor site shares overlapping but non-identical molecular determinants with BTX in D4S6 and has common molecular determinants in D1S6.

Dose-dependency in local disposition of 5-fluorouracil under non-steady-state condition in rat liver

Dose-dependency in local disposition of 5-fluorouracil (5-FU) was evaluated using the rat liver in the once-through perfusion system under the non-steady-state condition. A curve-fitting program based on Finite Element Method, MULTI(FEM), was adopted to evaluate the capacity-limited elimination in the hepatic local disposition of 5-FU, which is described by a nonlinear dispersion model with a pulse input. The dose of 5-FU was increased from 10.4 to 208 microg for rat livers at five dose levels. Two nonlinear models, two-compartment dispersion models with Michaelis-Menten elimination from the central compartment or from the peripheral compartment, were employed for comparison. The hepatic recovery ratio, F(H), increased from 13.1% to 68.3% and the mean transit time, t(H), increased from 5.1 to 13.1 s with an increase in the dose. It was found that the hepatic local disposition of 5-FU was well represented by the peripheral elimination model. V(max) and K(m) in the model with peripheral Michaelis-Menten elimination were estimated to be 9.04 mg/h and 2.88 mg/L, respectively. V(max) estimated by the present investigation in situ was about seven times greater than that in vitro, whereas K(m) in situ was close to that in vitro. This result suggests that the elimination activity by the hepatocytes in vitro may be lowered, compared with that in situ.

Differential effects of interleukin-4 and interleukin-10 on nitric oxide production by murine macrophages

OBJECTIVE

To study the effect of interleukin (IL)-4 and IL-10 on nitric oxide (NO) production by macrophages.

MATERIALS AND METHODS

Elicited or resident peritoneal macrophages (PMO) and a macrophage cell line Raw264.7 were primed by IL-4 or IL-10 for 6 hours, and were further incubated in the presence of interferon (IFN)-gamma and/or lipopolysaccharide (LPS) for 48 hours. NO2- accumulation in the supernatant of cultured cells was used as an indicator of NO production and was determined by the standard Griess reaction adapted for microplates. The amount of tumor necrosis factor (TNF)-alpha in the culture supernatants was determined with a commercially available ELISA kit. The absorbance was measured at 450 nm with a microplate photometer.

RESULTS

IL-4 inhibited NO production by murine macrophages of different sources and the macrophage cell line Raw264.7. In contrast, different macrophage populations showed differential responses to IL-10. After stimulation with LPS or IFN-gamma, IL-10 suppressed NO production by elicited PMO but enhanced NO production by resident PMO or by Raw264.7. Both IL-4 and IL-10 inhibited the production of TNF-alpha, which has been shown to play a crucial role in NO production. In the presence or the absence of blocking antibody to TNF-alpha, IL-10 always enhanced NO production by resident PMO. This result suggests that the inhibition of TNF-alpha production and the enhancement of NO production by resident PMO stimulated with IL-10 are independent, coexisting events.

CONCLUSIONS

Factors other than TNF-alpha have been suspected to influence NO production by macrophages, and this study indicates that IL-10 may be a candidate cytokine for resident PMO.

Low-dose gamma-ray irradiation reduces oxidative damage induced by CCl4 in mouse liver

We examined the effects of irradiation (50 cGy of gamma-ray) reducing the oxidative damage in carbon tetrachloride (CCl4)-hepatopathy mice. We made pathological examinations and analyzed transaminase activity (glutamic oxaloacetic transaminase and glutamic pyruvic transaminase), lipid peroxide level and the activities of endogenous antioxidants in the mouse. The irradiation was found to accelerate the recovery. Based on pathological examination as well as changes in each transaminase activity and lipid peroxide levels, it was shown that hepatopathy improved 3 d after the irradiation. The activities of glutathione reductase and glutathione peroxidase rapidly elevated after irradiation, and the total glutathione content gradually increased in the irradiation group. Both activities of gamma-glutamylcysteine synthetase and catalase were higher than normal at all times after the irradiation and gradually increased. In addition, the gamma-glutamylcysteine synthetase activity changed in a similar fashion to the total glutathione content. However, superoxide dismutase activity in both groups decreased and that of the irradiation group was significantly lower than that of the sham-irradiation group. These findings suggest that low-dose radiation relieved functional disorder at least in the liver of mice with active oxygen diseases.

Polymorphisms within the interleukin-10 receptor cDNA gene (IL10R) in Japanese patients with systemic lupus erythematosus

OBJECTIVE

To assess the association between polymorphisms within the interleukin-10 receptor cDNA gene (IL10R) and systemic erythematosus (SLE) in Japanese people.

METHOD

We examined the IL-10 receptor genotype of 109 SLE patients and 102 healthy subjects by the reverse transcription-polymerase chain reaction-restriction fragment length polymorphism (RT-PCR-RFLP) method.

RESULTS

There was no difference in the IL10R genotype frequencies of these two groups.

CONCLUSION

The IL10R genotype does not determine susceptibility to SLE in Japanese people.

Chemical characterisation of six oligosaccharides in a sample of colostrum of the brown capuchin, Cebus apella (Cebidae: primates)

Carbohydrates were extracted from a sample of brown capuchin colostrum and six of the component oligosaccharides were separated and purified by gel filtration and preparative thin layer chromatography. Their structures were determined by 1H-NMR to be as follows: Gal beta 1-->4[Fuc alpha 1-->3]Glc (3-fucosyllactose) Gal beta 1-->3Gal beta 1-->4Glc (beta-3'-galactosyllactose) Gal beta 1-->6Gal beta1-->4Glc (beta-6'-galactosyllactose) Gal beta-->3[Gal beta 1-->4GlcNAc beta 1-->6]Gal beta 1-->4Glc (lacto-N-novopentaose I) Gal beta 1-->4GlcNAc beta 1-->3[Gal beta 1-->4GlcNAc beta 1-->6]Gal beta 1-->4Glc (lacto-N-neohexaose) Neu5Ac alpha 2-->3Gal beta 1-->4Glc (3'-N-acetylneuraminyllactose) Of these, all except lacto-N-novopentaose I have been previously found in human milk or colostrum.

Elevation of glutathione in RAW 264.7 cells by low-dose gamma-ray irradiation and its responsibility for the appearance of radioresistance

We examined the relationship between the induction of glutathione (GSH) level in macrophage-like RAW 264.7 cells by a low (adapting) dose gamma-rays and the cell damage caused by a lethal dose of gamma-rays at various intervals after the adapting dose. The reduced glutathione (GSH) level increased soon after exposure of the cells to 25 cGy of gamma-rays, peaked between 3 hr and 6 hr, and returned almost to the zero time (0 hr) level by 24 hr post-irradiation. Cell damage was assessed by measuring the 3H-thymidine (3H-TdR) incorporation into cellular DNA. gamma-Ray irradiation produced a dose-dependent cell damage in RAW cells, causing about 40% and 60% inhibition of 3H-TdR incorporation into DNA at 1.0 Gy and 2.0 Gy, respectively, as compared with non-irradiated cells. Treatment with the adapting dose of 25 cGy at 1 hr or 24 hr before the lethal irradiation was ineffective. However, pre-irradiation with 25 cGy at 3 hr or 6 hr prior to lethal irradiation inhibited the decrease of 3H-TdR incorporation into DNA, indicating a protective effect. GSH exogenously added to the medium also inhibited the cell damage induced by lethal doses of gamma-Rays in a dose-dependent manner. These results indicate that the induction of endogenous GSH in living cells immediately following low-dose gamma-Ray irradiation is at least partially responsible for the appearance of radioresistance to a subsequent lethal dose of radiation, and may make it possible to use higher doses of radiation in radiotherapy for tumor patients.

Changes of SOD-like substances in mouse organs after low-dose X-ray irradiation

We demonstrated that low-dose irradiation with 50 cGy of X-ray induces in vivo production of superoxide dismutase (SOD)-like substances and accelerates antioxidant activity. To elucidate the defense mechanism against X-ray radiation, we examined which components among these SOD-like substances, such as SOD, vitamin C and celuroplasmin, are produced by low-dose irradiation. Our study revealed that SOD-like specific activity hardly involved SOD-like substances other than SOD. Moreover, it is suggested that low-dose irradiation induced synthesis and production of SOD itself, leading to elevation of SOD-specific activity.

Point-mutations related to the loss of batrachotoxin binding abolish the grayanotoxin effect in Na(+) channel isoforms

The effect of grayanotoxin (GTX) on site-specific mutants of the alpha-subunit of rat skeletal muscle Na(+) channels (micro1) (micro1-I433K, micro1-N434K and micro1-L437K), which are resistant to batrachotoxin (BTX) (Wang and Wang (1998) Proc Natl Acad Sci USA, 95, 2653-2658) was studied using a whole-cell patch-clamp method. The GTX modification of the Na(+) channels was detected as a characteristic-sustained Na(+) current flow with repetitive pulses. We also studied the GTX action on mutants of the alpha-subunit of rat heart Na(+) channels (RH1) (RH1-V406K and RH1-L410K) which match with micro1-I433 and micro1-L437. All the mutants lost their sensitivity to GTX. This finding indicates that GTX may share a binding site with BTX in transmembrane segment I-S6 of two different Na(+) channel isoforms, micro1 and RH1.

[Validity of urinary glucose test for diabetes screening in workplace regular medical checkups]

It has been acknowledged that urinary glucose level varies depending on the time after meal which may hence affect validity of urinary glucose test as a screening test for diabetes. However, sample collection time has not been standardized for urinary glucose test in workplace regular medical checkups. In this study, we investigated the effect of timing of urine sampling on results of urinary glucose screening tests, and using data obtained from the 75 g oral glucose tolerance tests (OGTT) evaluated the validity of urinary glucose test in workplace medical checkups. Also, we made a survey among industrial physicians about the timing of sample collection. Between 1991 and 1996, 455 males and 116 females who participated in a 2-day health examination including the OGTT in a hospital in Chiba were used as study subjects. These did not include an additional 22 subjects who had already been diagnosed as having diabetes but received the OGTT. The examinees observed a strict fast after supper the previous evening and urine and blood samples were collected before and 2 hours after glucose intake for the OGTT. Diagnosis of diabetes was made following the criteria of WHO (1985) and screening test results were defined positive when urinary glucose level was equal to or more than 40 mg/dl. Sensitivity and specificity were calculated for diabetes and impaired glucose tolerance separately for male and female. Industrial physicians who participated in a lecture course for qualification were surveyed about the timing of urine sample collection for urinary glucose test in workplace regular medical checkups. For the urine samples collected 2 hours after glucose intake, sensitivity was very high (male 84%, female 100%), in addition to a relatively high specificity (male 71%, female 92%). However the samples collected before glucose intake showed extremely poor sensitivity (male 11%, female 0%). Similar results were obtained when screening was made for impaired glucose tolerance and both diabetes and impaired glucose tolerance combined. The survey among the industrial physician revealed that in the majority (58%) of workplace medical checkups, the urine sample had been collected when examinees were fasting. The largest reason for this was that the urinary glucose test was performed together with upper gastro-intestinal examination or measurement of serum triglyceride both of which require fasting of examinees. The results of the present study showed that urinary glucose tests have been frequently performed at a timing that produces low validity. The procedures of workplace regular medical checkups should be evaluated with the concept of Evidence Based Medicine. The standard of the timing of urine sample collection for urinary glucose test should be carefully examined.

The electric dipole moment of DNA-binding HU protein calculated by the use of an NMR database

Electric birefringence measurements indicated the presence of a large permanent dipole moment in HU protein-DNA complex. In order to substantiate this observation, numerical computation of the dipole moment of HU protein homodimer was carried out by using NMR protein databases. The dipole moments of globular proteins have hitherto been calculated with X-ray databases and NMR data have never been used before. The advantages of NMR databases are: (a) NMR data are obtained, unlike X-ray databases, using protein solutions. Accordingly, this method eliminates the bothersome question as to the possible alteration of the protein structure due to the transition from the crystalline state to the solution state. This question is particularly important for proteins such as HU protein which has some degree of internal flexibility; (b) the three-dimensional coordinates of hydrogen atoms in protein molecules can be determined with a sufficient resolution and this enables the N-H as well as C = O bond moments to be calculated. Since the NMR database of HU protein from Bacillus stearothermophilus consists of 25 models, the surface charge as well as the core dipole moments were computed for each of these structures. The results of these calculations show that the net permanent dipole moments of HU protein homodimer is approximately 500-530 D (1 D = 3.33 x 10(-30) Cm) at pH 7.5 and 600-630 D at the isoelectric point (pH 10.5). These permanent dipole moments are unusually large for a small protein of the size of 19.5 kDa. Nevertheless, the result of numerical calculations is compatible with the electro-optical observation, confirming a very large dipole moment in this protein.

Th1/Th2 balance of peripheral T helper cells in systemic lupus erythematosus

OBJECTIVE

To analyze the Th1/Th2 balance of peripheral Th cells in patients with systemic lupus erythematosus (SLE).

METHODS

The Th1:Th2 ratio was analyzed in 3 groups: SLE without proteinuria (group I; n = 23), SLE with proteinuria (group II; n = 31), and normal controls (group III; n = 24). Group II patients who had undergone renal biopsy were classified into 3 subgroups based on their renal histopathologic findings. The intracellular cytokine detection method with flow cytometry was used to quantitate Th1 and Th2 cells.

RESULTS

There was no difference in the mean Th1:Th2 ratio between SLE patients (groups I and II) and healthy controls (group III). However, the mean value in group II was significantly higher than those in groups I and III. Moreover, within group II, the mean value in SLE patients who had diffuse proliferative lupus nephritis (World Health Organization class IV) was especially high.

CONCLUSION

Although SLE has been considered to be a disease in which Th2 cells predominate, the Th1/Th2 balance of peripheral Th cells in SLE patients in the present study did not show a predominance of these cells. In contrast, among SLE patients with WHO class IV lupus nephritis, there was a strong predominance of Th1.

Regulation of L- and N-types of Ca2+ channels by intracellular ATP4- in frog dorsal root ganglion neurons

The roles of free Mg2+ ions, ATP4- ions and Mg-ATP complexes in the regulation of N- and L-types of Ca2+ channels were studied in frog dorsal root ganglion (DRG) neurons using the whole-cell patch-clamp technique. Because Mg2+ ions interact with ATP4- ions to form Mg-ATP complexes, addition of one species can influence the concentrations of the other two. In this study their concentrations were carefully controlled by varying the concentrations of two constituents at a time while keeping the third constant. The effects of each of the three species on barium currents through L-type (IBaL) and N-type (IBaN) Ca2+ channels were plotted against its concentrations. The dose-response curves for ATP4- show that IBaL and IBaN proportionally increased with ATP4- concentrations up to 1 mM at three different Mg2+ concentrations. At a fixed concentration of ATP4-, IBaL and IBaN remained unchanged even when pMg changed from 3 to 5. Dose-response curves for IBaL and IBaN plotted against Mg-ATP concentration did not show a consistent pattern. H-7 and Mg2+ ions did not exert any blocking effect on the activity of either Ca2+ channel type, and neither dibutyryl-cAMP nor NKH-477 had any stimulating effect, suggesting that phosphorylation is not likely to be involved in ATP-induced potentiation. From these observations, it is concluded that L-type and N-type Ca2+ channels in frog DRG neurons are regulated by ATP4- ions alone, and that the neuronal Ca2+ channels are regulated by mechanisms that are different from those regulating the cardiac Ca2+ channels.

The combination of polymorphisms within interferon-gamma receptor 1 and receptor 2 associated with the risk of systemic lupus erythematosus

Genetic factors seem to play a significant role in susceptibility to systemic lupus erythematosus (SLE). We previously described the amino acid polymorphism (Val14Met) within the IFN-gamma receptor 1 (IFN-gammaRI), and that the frequency of the Metl4 allele in SLE patients was significantly higher than that of the healthy control population [Tanaka et al. (1999) Immunogenetics 49, 266-271]. We also found an amino acid polymorphism (Gln64Arg) within IFN-gamma receptor 2 (IFN-gammaR2). Since the IFN-gamma receptor is a complex consisting of IFN-gammaR1 and IFN-gammaR2, we searched for the particular combination of two kinds of amino acid polymorphisms found within the IFN-gamma receptor which plays a prominent role in susceptibility to SLE. The greatest risk of the development of SLE was detected in the individuals who had the combination of IFNGR1 Met14/Val14 genotype and IFNGR2 Gln64/Gln64 genotype.

Selective DNA-binding activity of interleukin-10-stimulated STAT molecules in human monocytes

It has been demonstrated that interferon-gamma (IFN-gamma) and interleukin-10 (IL-10) have various reverse effects on macrophages; however, the molecular mechanism of this difference has not been fully understood. In this study, we analyzed the binding activity of IL-10- and IFN-gamma-activated STAT molecules to two kinds of GAS-motif sequences. IL-10-activated STAT1 could bind to the GAS-motif sequence in the promoter region of the Fcgamma receptor, but not to that in the promoter region of the COX-2 gene, whereas IFN-gamma-activated STAT1 and STAT5 could bind to both sequences. IL-10 inhibited IFN-gamma-induced STAT activation without newly synthesized protein. We further demonstrated that aspirin, but not dexamethasone, suppressed IFN-gamma-induced STAT activation. Taken together, these results suggest that IL-10-activated STAT1 has a specificity in binding to the GAS-motif sequences, whereas IFN-gamma-activated STAT1 and STAT5 have a broader spectrum in binding to the GAS-motif sequences. This may explain the difference between IL-10 and IFN-gamma in biological activity, and the inhibitory effect of IL-10 on IFN-gamma activities.

Chemical characterisation of the oligosaccharides in a sample of milk of a white-nosed coati, Nasua narica (Procyonidae: Carnivora)

Carbohydrates were extracted from a sample of coati milk and the component oligosaccharides were separated and partially purified by gel filtration and preparative thin layer chromatography. Their structures were determined by 1H-NMR. Fuc alpha 1-->2Gal beta 1-->4Glc Gal alpha 1-->3Gal beta 1-->4Glc Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1-->4Glc Fuc alpha 1-->2Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1-->4Glc Gal alpha 1-->3Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1-->4Glc The two pentasaccharides are novel sugars. In addition, higher oligosaccharides, whose core units were lacto-N-neohexaose, were found in coati milk. Free lactose constituted only about one-third of the total free milk saccharides. The results are discussed in terms of comparisons with the milk sugars of bears and other species.

Analysis program based on finite element method, MULTI(FEM), for evaluation of dose-dependent local disposition of drug in liver

A curve-fitting program based on the Finite Element Method, MULTI(FEM), was developed to model nonlinear local disposition of a drug in the liver under non-steady-state conditions. The program was written in FORTRAN on an IBM-compatible personal computer. The validity of MULTI(FEM) was confirmed by analyzing the outflow kinetics of oxacillin (a model drug) following a pulse input to isolated, perfused rat livers, according to both linear and nonlinear dispersion models. Four dose levels (300, 1000, 3000, and 5000 microg) of oxacillin were administered to observe the dose-dependency in the hepatic local disposition. First, the individual outflow time-profiles at the same dose were averaged, and the average time-profile was analyzed by MULTI(FEM) based on linear dispersion models to yield a single curve fit. The fitted parameters at each dose level were compared with parameters estimated using MULTI(FILT), a program based on fast inverse Laplace transform, to analyze linear pharmacokinetics. The estimated parameters by MULTI(FEM) were in good agreement with those by MULTI(FILT). The apparent elimination rate constant (ke) decreased with an increase in dose, whereas other parameters showed no discernible dependency on an increase of dose. Second, the average outflow time-profiles at the four dose levels were simultaneously analyzed by MULTI(FEM) based on dispersion models featuring Michaelis-Menten elimination. The outflow time-profiles of oxacillin were well approximated by a two-compartment dispersion model with central Michaelis-Menten elimination. The maximum elimination rate constant (Vmax) and the Michaelis constant (Km) were estimated to be 1520 microg/mL/min and 41.3 microg/mL, respectively. Thus, the capability of MULTI(FEM) was demonstrated in evaluating capacity-limited local disposition in the liver.

Effect of pentobarbital anaesthesia on intestinal absorption and hepatic first-pass metabolism of oxacillin in rats, evaluated by portal-systemic concentration difference

The effects of anaesthesia on intestinal drug absorption and hepatic first-pass metabolism in rats were investigated by observing the difference in the drug concentration between portal and systemic bloods. Oxacillin and pentobarbital were selected as a model drug and as an anaesthetic, respectively. Rats were divided into a conscious control group and an anaesthetized group. All rats were cannulated simultaneously in the portal vein and in the femoral artery, and oxacillin was orally administered after its intra-arterial injection (double dosing). For the anaesthetized group, pentobarbital was intrasubcutaneously administered twice, first before intra-arterial injection and again before oral administration of oxacillin. The arterial blood alone was sampled from the cannula in the femoral artery before oral administration, whereas the arterial and portal bloods were simultaneously sampled from both cannulated sites after oral administration. Oxacillin concentrations in plasma were assayed by HPLC. The anaesthesia increased the absolute bioavailability (F), the mean absorption time (MAT) and the hepatic recovery ratio (F(H)), but caused little change in the local absorption ratio into the portal system (Fa) and the total clearance (CL). The hepatic clearance (CL(H)) was significantly decreased, resulting in an apparent small change in CL-CL(H) which is considered to be renal clearance. By this method, it was shown directly that an increase in F due to pentobarbital anaesthesia was attributable to the significant increase in F(H). It is expected that the method is useful not only to evaluate the effect of anaesthesia on the first-pass effect, but also to assess the effect of co-administration of drugs on first-pass metabolism.

Oxygen concentration regulates NO-dependent relaxation of aortic smooth muscles

Nitric oxide (NO) functions as an endothelium-derived relaxation factor and regulates vascular resistance. Recent studies in this laboratory(Arch.Biochem.Biophys.323, 27-32, 1995) revealed that the lifetime of NO significantly increased at physiologically low levels of oxygen concentrations and, hence, this gaseous radical strongly inhibited mitochondrial electron transport for a fairly long duration at low oxygen concentrations. The present work describes the effect of oxygen concentration on NO-induced relaxation and guanylate cyclase (GC) activity of endothelium-denuded aorta of the rat. Both NO and 2,2 '-(hydroxynitrosohydrazono)bis-ethanamine (NOC18), an NO donor, induced the relaxation of endothelium-denuded helical segments of rat aorta which were contracted by norepinephrine. NO-dependent relaxation of arterial specimens was enhanced by lowering oxygen concentration in the medium with concomitant increase in their cGMP levels. Anoxia induced the relaxation of the aorta by some NO-enhanceable and methylene blue-insensitive mechanism. These results suggested that local concentrations of oxygen might play important roles in the regulation of NO-dependent GC activity and vascular tonus of resistance arteries.