Biomedical subjects

M Iwaki

Publications and source records attributed to M Iwaki.

At least 145 records · Page 8Linked to original sources

PubMed1990

Oral immunization with recombinant Streptococcus lactis carrying the Streptococcus mutans surface protein antigen gene.

A recombinant Streptococcus lactis strain which carries the structural gene for a surface protein antigen (PAc) of 190,000 daltons from Streptococcus mutans serotype c was constructed for development of an oral vaccine against dental caries. The gene from S. mutans MT8148 joined to shuttle vector pSA3 was successfully transformed into S. lactis IL1403. A small amount of PAc was detected in the cell homogenate and cytoplasmic fraction of the recombinant S. lactis, but not in the culture supernatant of the recombinant, by Western immunoblotting and dot immunoblotting. The level of PAc-specific mRNA in the recombinant strain was lower than that in S. mutans MT8148. However, significant salivary immunoglobulin A and serum immunoglobulin G responses to PAc were induced in mice immunized orally with the recombinant S. lactis.

Animals↗

PubMed1990

Inhibitory effect of valproic acid on metabolic clearance of carbamazepine epoxide.

In order to clarify the inhibitory effect of valproic acid (VPA) on the metabolic clearance of carbamazepine-10,11-epoxide (EPO), an active metabolite of carbamazepine, in rat, the disposition of EPO from plasma and the in vitro hydration of EPO were measured in the presence of VPA, in addition to estimating the effect of the antiepileptic on uridine 5'-diphosphoglucuronyltransferase (UDPGT) activity. It was found that the elimination of EPO from plasma was hardly affected by the pretreatment of VPA (100 mg/kg/d for 7 d). However, the elimination was significantly delayed by VPA at steady-state concentration, maintained by the repeated oral administration of the drug, with a 38% decrease in total clearance and a 52% increase in the fraction of EPO eliminated unchanged in urine. The in vitro hydration of EPO was inhibited competitively by VPA at the concentrations comparable to the in vivo levels. The UDPGT activity of hepatic microsomes was also partly inhibited by VPA. These results suggest that VPA at steady state interferes with the metabolic clearance of EPO, by inhibiting the hydration of EPO and glucuronidation of carbamazepine-trans-diol, a hydrated metabolite.

Animals↗

PubMed1990

Drug interaction between phenytoin and allopurinol.

The combination of phenytoin (DPH) and allopurinol is used for the treatment of a neurological disease. However, interactions between DHP and allopurinol and the mechanism are little known. The repeated dosing of allopurinol at higher doses (20 and 50 mg/kg) significantly retarded the elimination of DPH from the circulation and dramatically decreased the urinary excretion of p-hydroxyphenytoin (HPPH), a major metabolite of DPH. However, a single administration of allopurinol (10 or 50 mg/kg) did not give rise to these effects. Allopurinol did not affect the hepatic extraction of DPH and renal plasma flow rate. Allopurinol (50 mg/kg/d) dosed repeatedly could not inhibit the hepatic drug metabolizing enzyme activities. The in vitro hydroxylation of DPH was inhibited only slightly and the kinetic plots gave apparently non-competitive inhibition. The less inhibitory effect of allopurinol on the in vitro hydroxylation did not agree with the in vivo data. These results indicate that the inhibitory effect of allopurinol is not mediated by cytochrome P-450 dependent monooxygenase reactions.

Administration, Oral↗

PubMed1990

Pharmacokinetics and first-pass effect of bromhexine in rats.

The pharmacokinetics and first-pass effect of bromhexine (BH) were studied in rats. Upon i.v. administration of 0.3 and 1 mg/kg of BH hydrochloride to normal rats, the plasma concentrations followed a biexponential curve, with slower terminal elimination (t1/2 beta = 8.9-11 h). In bile duct cannulated rats, the plasma concentration-time profile was similar to that of normal rats and the bile excreted within 30 h contained only 1.5 +/- 1.2% of the dose as intact and conjugated BH. These results suggest that a slower terminal elimination of BH after i.v. injection is due to a relatively small plasma clearance and large distribution volume rather than the enterohepatic recycling of the drug. Renal clearance of BH was negligible since urinary excretion of intact BH for 24 h after i.v. injection did not exceed 1% of the dose. After oral administration of BH, the systemic availability ranged only 1.8-3.9% based on i.v. and oral data, showing the poor bioavailability of oral BH. The first-pass effect of BH was measured by comparing the area under plasma concentration-time curve (AUC) after i.v., oral or hepatic portal (h.p.v.) administration of the drug. The AUC following h.p.v. dosing was only one-tenth of that obtained following i.v. administration and the AUC after oral dose was a quarter of that after h.p.v. administration. The hepatic extraction ratio was estimated to be 0.92. A low bioavailability after oral BH was explained by both hepatic and intestinal first-pass clearance, but mainly due to hepatic extraction.

Administration, Oral↗

PubMed1990

Percutaneous absorption of 1,3-dinitroglycerin and a trial of pharmacokinetic analysis.

In order to estimate the pharmaceutical usefulness of 1,3-glyceryl dinitrate (1,3-GDN), an active metabolite of nitroglycerin, a trial transdermal delivery system designed to sustain a suitable plasma concentration of 1,3-GDN was produced using a porous membrane (Hipore 2100 or 4500) and it was a gel base or ethylhexyl acrylate-based adhesive (adhesive) and it was applied to rats. Additionally, for practical use of the transdermal system, a simple pharmacokinetic model to describe plasma 1,3-GDN levels after percutaneous (p.c.) application is presented. As a result, the drug was penetrated through the rat skin in vitro at a zero-order rate, although the penetration rate from the gel base was significantly greater than that from the adhesive. In vivo, the drug was rapidly absorbed through the rat skin, with a peak plasma level of 581 +/- 151 and 265 +/- 62 ng/ml for the gel ointment and adhesive systems without a porous membrane, respectively. The plasma levels after application of the systems with a membrane were relatively constant for a long time, indicating that the membranes act as a controlled-release barrier. The bioavailability of 1,3-GDN after gel base systems with and without a membrane was relatively high. The model presented was successfully able to describe the time course of plasma 1,3-GDN concentrations following p.c. application of the systems.

Administration, Topical↗

PubMed1990

Pharmacological studies on 6-amidino-2-naphthyl[4-(4,5-dihydro-1H-imidazol-2-yl)amino] benzoate dimethane sulfonate (FUT-187). I: Inhibitory activities on various kinds of enzymes in vitro and anticomplement activity in vivo.

FUT-187, a newly synthesized compound, was studied on its inhibitory activities mainly on proteolytic enzymes, in comparison with those of FUT-175 and FOY-305, known serine protease inhibitors. FUT-187, as well as FUT-175 and FOY-305, had selective inhibitory activities on serine proteases including Clr, Cls, kallikrein, trypsin, plasmin and thrombin; its activities on these enzymes except Clr and pancreatic kallikrein were relatively lower than those of FUT-175 and FOY-305. Further studies were conducted focusing on complement-mediated reactions. In spite of its lower activities against Clr and Cls, inhibitions by FUT-187 on the complement-mediated hemolysis in vitro and in vivo were only a little weaker than or equivalent to that of FUT-175. FOY-305 was ineffective in these tests. Forssman shock in guinea pigs is known to be initiated by the activation of the complement system. The protective effect of intravenous or oral FUT-187 against this shock was definitely superior to that of FUT-175. Furthermore, FUT-187 inhibited changes accompanied with Forssman shock, such as increase in lung weight, the decrease in platelet counts and CH50, and histopathological changes. These results suggested that FUT-187 should be a more potent oral therapeutic agent than FUT-175 for various inflammatory diseases attributed to the excessive activation of the complement system followed by platelet aggregation.

Amylases↗

PubMed1989

A pharmacokinetic model for the percutaneous absorption of indomethacin and the prediction of drug disposition kinetics.

A pharmacokinetic model with two parallel absorption processes from two fractions has been derived for the percutaneous absorption of indomethacin. The simulation includes five first-order rate constants assigned the following significance: (a) rapid absorption (ka1) and slow absorption (ka2) through the skin; and (b) distribution into the tissue and subsequent elimination from the body. The model, applied to data obtained after percutaneous dosing of ointments under occlusion, successfully described the plasma profile observed in the presence and absence of laurocapram (Azone) and sorbitan monooleate. The penetration characteristics through stripped skin were also well described by the model. It was clarified that indomethacin was absorbed via both pathways, with rapid and slow absorption rate constants at the initial time stage, and via the latter pathway at the later period. Also, laurocapram and sorbitan monooleate increased the fraction absorbed via the rapid absorption pathway by about three times, without a significant alteration of either absorption rate constant, while the enhancers gave no significant effect on either absorption pathway in the stripped skin. The results suggest that the model is simple yet adaptable enough to prove of general use for the interpretation of percutaneous absorption data.

Animals↗

PubMed1989

Pharmacokinetics and biotransformation of hydralazine acetone hydrazone, a metabolite of hydralazine, in the rat.

The pharmacokinetics of hydralazine acetone hydrazone (HAH), which is a metabolite of hydralazine (HP), was investigated after iv administration to rats. Plasma concentrations of HAH, HP, and hydralazine pyruvic acid hydrazone (HPH) were simultaneously determined by a specific HPLC method. A five-compartment pharmacokinetic model was presented to elucidate the disposition of HAH and two products, HP and HPH. The parameters used in the model were obtained by administering each of the three compounds (10 mg/kg) separately. The proposed model described the experimental data well and the model parameters were close to the model-independent values. After HP administration, HPH appeared rapidly in plasma, but the HPH availability from HP amounted to only 17.8 +/- 3.7%, based on the comparison between the area under the plasma concentration curves of formed and iv HPH. The formation of HP from HAH in the systemic circulation was demonstrated, but formed HP disappeared rapidly. The fraction of HAH available to the systemic circulation as HPH was extremely low (7.8 +/- 2.2%), indicating that the conversion of HAH to HP was not so extensive. The present results support the hypotheses that HPH is formed via the direct reaction of HAH with pyruvic acid and that the secondary formation is mediated by conversion to HP.

Animals↗

PubMed1989

Characterization of the proteases in the crude mite extract.

Characterization of the proteases was performed in the crude mite extract fractionated by Sephacryl S-200 gel filtration. Three peaks of protease activities were detected in the fractions. From the results of substrate specificity and susceptibility to the inhibitors, PK.1 protease (about 60 kD) is suggested to be a trypsin-like protease of mites. From the results of susceptibility to various agents, PK.2 (about 30 kD) and PK.3 (about 20 kD) proteases may be cysteine proteases, e.g., papain and cathepsin B. PK.3 protease existed in the precipitate of 60% ammonium sulfate fractionation. The data in the present study suggest the possibility that Dermatophagoides farinae I allergen might be a cysteine protease probably derived from the gastrointestinal tract of the house dust mite.

Allergens↗

PubMed1989

Encapsulation of porcine insulin in rabbit erythrocytes and its disposition in the circulation system in normal and diabetic rabbits.

The application and usefulness of resealed erythrocytes as a cell carrier of porcine insulin were studied in rabbits. The insulin was loaded in rabbit erythrocytes by a dialysis method followed by isotonic resealing of the erythrocytes at 25 and 37 degrees C. The amounts of insulin entrapped in the erythrocytes at these temperatures were 6.23 +/- 1.05 and 5.89 +/- 1.33 IU/ml of packed cell, with efficiency of encapsulation being 6.0 +/- 1.2 and 5.8 +/- 2.0%, respectively. When the insulin loaded erythrocytes were incubated in phosphate buffered saline at 37 degrees C, the insulin levels in the resealed cells declined according to a biexponential function. The in vitro stability of the cells resealed at 25 degrees C was superior to that at 37 degrees C. After subcutaneous (s.c.) administration of free insulin, the absorption rate constants in diabetic rabbits were larger than those of normal rabbits. The in vivo decline of insulin released from the loaded erythrocytes indicated a biexponential kinetics. Although the pharmacokinetic behavior of plasma insulin between normal and diabetic rabbits was similar, the hypoglycemic effect was very different between them. These insulin dosings, be they intravenous (i.v.) dosing of insulin or loaded cells or s.c. dosing of insulin, maintained the hypoglycemic effect in diabetic rabbits about twice as long as in a normal animal. Moreover, the effective period of insulin-loaded erythrocytes was longer than that of free insulin dosings. These results suggest that the insulin-loaded erythrocytes may be useful as a dosage form for treatment of patients with diabetes mellitus.

Animals↗

PubMed1989

In vitro stability of insulin-loaded erythrocytes after freezing storage.

In order to clarify the utility of resealed erythrocytes as a cell carrier of insulin the freezing stabilities of loaded cells encapsulating two different amounts of insulin (about 0.1 and 7.0 IU/ml of packed cells) were investigated in an anti-freezing reagent containing a high concentration of glycerol at -80 degrees C. After storing for 1 week under the above condition the preparation was thawed at 37 degrees C. Although the osmotic resistance of the loaded cells was lowered more than that of intact cells, the freezing and thawing treatment did not change the resistance of the loaded cells to osmotic shock. Recoveries of hemoglobin from loaded cells with a low insulin content (0.1 IU/ml of cells) and the cell volume after freezing and thawing were similar to those from intact cells and the cells resealed without insulin. However, the recovery of insulin from the cells with a high insulin content (7.0 IU/ml of cells) was the same as that from one with a low insulin content (about 16%). In the in vitro stability experiment at 37 degrees C the insulin content in the loaded cells decreased according to a biexponential function. The considerable fraction of the loaded cells were lysed by freezing and thawing. In the in vitro stability experiment the decline curve of insulin in the cells showed apparently monoexponential kinetics. From these results, it was established that insulin-loaded erythrocytes may be stored in a high concentration of glycerol under freezing at -80 degrees C, although a partial decrease in the stability of cells was observed after thawing.

Animals↗

PubMed1989

Effects of anticonvulsants on plasma levels and entero-hepatic circulation of valproic acid and on hepatic drug metabolizing enzyme activities in rats.

To clarify the interaction between valproic acid (VPA) and anticonvulsive drugs such as phenytoin (DPH), phenobarbital (PB) and carbamazepine (CBZ), the effects of these anticonvulsants on the plasma levels and enterohepatic circulation of VPA and on drug metabolizing enzyme activities in liver in relation to their inductive effects were investigated in rats. After intravenous (i.v.) or oral administration, plasma VPA rapidly decreased, and this was followed by a secondary increase in plasma level of VPA due to enterohepatic circulation. When the drug was repeatedly coadministered with DPH or CBZ, the initial VPA elimination from plasma up to 1 h after dosing was less than with VPA alone, while PB significantly enhanced the disappearance of VPA. Judging from the decrease in the area under plasma VPA concentration-time curve from 2 to 9 h (AUC2-9), the enterohepatic circulation of VPA was also decreased by PB, but not by DPH and CBZ. The in vitro and in vivo protein binding of VPA was almost unchanged in the presence of DPH. Cytochrome P-450 content and glucuronyltransferase activity were enhanced following repeated coadministration with PB, DPH or CBZ. These enzyme activities in the animals treated with VPA alone at various dosage levels, however, remained unchanged, indicating that VPA did not inhibit the hepatic drug metabolizing enzyme activities in rats.

Animals↗

PubMed1989

Effect of phenylhydrazine-induced structural alterations of human erythrocytes on basic drug penetration.

The phospholipid organization, lipid fluidity and spectrin degradation were measured in human erythrocytes oxidized with phenylhydrazine, and the contribution of these structural alterations to the penetration of perazine and promethazine into the membrane was estimated. It was found that exposure of erythrocytes to phenylhydrazine (0.2--0.4 mg/ml) produced a 35--40% decrease in the amount of spectrin, with resultant gross morphological changes to the echinocyte conformation. The phosphatidylethanolamine content in the treated erythrocytes was greatly lowered compared with that in the untreated cells. Treatment with phenylhydrazine (0.05--0.2 mg/ml) dramatically diminished the lipid fluidity of the membrane, as estimated by electron spin resonance (ESR) spectrometry, and the ESR study revealed increased restriction of the molecular motion of the hydrophobic core in the treated membrane. These results suggest a drastic alteration of the erythrocyte membrane structure. The amount of drugs which penetrated into the treated erythrocytes increased markedly with increasing phenylhydrazine concentration, suggesting enhanced membrane permeability and facilitated localization of the drugs in the hydrophobic regions due to the structural changes and partial disturbance of the lipid organization.

Erythrocytes↗

PubMed1989

Percutaneous absorption of clonazepam in rabbit.

The percutaneous (p.c.) absorption of clonazepam (CZP), an antiepileptic drug, was investigated in rabbits. CZP was efficiently absorbed from a gel ointment (0.5% CZP, 1g, 9 cm2) with Azone and therapeutic plasma concentrations were maintained for 27 h. The bioavailability of CZP from the gel ointment was 47.2 +/- 3.1%, which was significantly larger than that (3.3 +/- 0.5%) after the ointment without Azone or that (12.5 +/- 3.6%) after oral administration. About a half of CZP in the ointment with Azone was absorbed during a 24 h application. The maximum and minimum plasma concentrations and the area under the plasma concentration-time curve gradually increased during repeated application of the ointment (2% CZP, 0.25 g/d, 2.25 cm2), probably due to the accumulation of drug in the skin and body. The efficient absorption and sustained plasma concentration of CZP after application suggest that a once a day p.c. administration regimen is possible by using the ointment with Azone.

Administration, Oral↗

PubMed1989

Membrane-controlled transdermal therapeutic system containing clonazepam and anticonvulsant activity after its application.

A trial transdermal dosage form designed to sustain a suitable plasma concentration of clonazepam (CZP) was produced using a porous membrane (Hipore 2100 or 4050) and applied to rabbits and rats for pharmacokinetic and pharmacodynamic evaluations. The release rate constants for the drug through the porous membranes were significantly smaller than that without any membrane. The transdermal system (Hipore 4050 system, ointment 0.25 g, 2.25 cm2) provided a well sustained plasma concentration of CZP and the therapeutic plasma concentration range was maintained for about 26 h. When the Hipore 4050 system with an increased amount of ointment and enlarged absorption area (0.5 g, 4.0 cm2) was applied, the therapeutic range was sustained for about 40 h, and slightly higher plasma levels over the whole application period and much higher bioavailability (37%) were obtained compared with those after the 2.25 cm2-Hipore 4050 system. The transdermal system exerted an excellent anticonvulsant activity in rats, with the best (3+ or 4+) protective score. The plasma concentrations of CZP when the activity was estimated were in the therapeutic range. Thus, the transdermal system has the potential to be an efficient drug delivery system.

Administration, Cutaneous↗

PubMed1989

[Inhibitory effect of N-alpha-[(S)-1-carboxy-3-phenylpropyl]-L-lysyl-L-proline (MK-0521) on angiotensin converting enzyme in vitro].

N-alpha-[(S)-1-carboxy-3-phenylpropyl]-L-lysyl-L-proline (MK-0521) is a new non-sulfhydryl-containing angiotensin converting enzyme (ACE) inhibitor. The present investigation describes its ACE and other enzymes inhibitory properties and compares it to those of captopril, MK-421 and MK-422 in vitro. MK-0521 inhibited rat pulmonary ACE by 50% (IC50) at a concentration of 3 nM and was 6.13 times more potent than captopril. The IC50 values of MK-421 and MK-422 against ACE were 2,000 nM and 3.5 nM, respectively. MK-0521 had practically no inhibitory activities against carboxypeptidase A, carboxypeptidase B, leucine aminopeptidase, papain, pepsin and trypsin. The kinetic study on the inhibitory activity of M-0521 against ACE using Lineweaver-Burk plots indicated that MK-0521 exerted competitive ACE inhibition. The dialysis study conducted on the ACE-MK-0521 complex revealed that the inhibitory effect of MK-0521 against ACE was reversible. In the guinea pig ileum, MK-0521 potentiated the contractile effect of bradykinin and depressed the contractile effect of angiotensin I. These effects on bradykinin and angiotensin I were 33.11 and 2.63 times more potent than that of captopril, respectively. The present results suggest that MK-0521 may show a potent hypotensive effect in vivo.

Angiotensin I↗

PubMed1989

[Angiotensin converting enzyme inhibitory activity of MK-0521 in vivo and antihypertensive effect of its single oral administration on blood pressure and effect on the renin-angiotensin system in 2-kidney Goldblatt hypertensive dogs].

Angiotensin converting enzyme (ACE) inhibitory activity of MK-0521 in dogs and the effects of its single oral administration on blood pressure and the renin-angiotensin system in 2-kidney Goldblatt hypertensive dogs were compared with those of captopril and MK-421. MK-0521 at 0.001-0.1 mg/kg, i.v., or 0.01-1 mg/kg, p.o., attenuated the pressor effect of angiotensin I without affecting that of angiotensin II and augmented the depressor effect of bradykinin. The potency of MK-0521 to reduce the pressor effect of angiotensin I was 9.8 times that of captopril by intravenous administration, and by oral administration, it was 15.9-32.1 times that of captopril and approximately 3 times that of MK-421. When administered orally, the onset of action and the time to peak effectiveness were more rapid than those of MK-421, but slower than those of captopril. Duration of the action of MK-0521 was longer than that of captopril and equal or longer than that of MK-421. The inhibition of ACE was well correlated with serum MK-0521 levels. MK-0521 produced a dose-dependent antihypertensive effect in 2-kidney Goldblatt hypertensive dogs at over 0.3 mg/kg, p.o., without affecting the heart rate. The antihypertensive effect of MK-0521 was persistent and approximately 3 times more potent than that of captopril. MK-0521 inhibited the serum ACE activity and increased the plasma renin activity, while it had a tendency to decrease plasma aldosterone level. These changes were parallel to the time course of the antihypertensive effect. These results suggest that the main mechanism of the antihypertensive effect of MK-0521 is the suppression of angiotensin II production due to the inhibition of the ACE.

Administration, Oral↗

PubMed1989

[Antihypertensive effect of repeated oral administration of MK-0521 in 2-kidney Goldblatt hypertensive dogs].

MK-0521 and captopril were orally administered to acute (6 to 8 days after unilateral renal artery constriction) and chronic (2 to 2.5 months after the constriction) 2-kidney Goldblatt hypertensive dogs for 7 to 21 days. MK-0521 lowered the blood pressure to similar extents in the acute and chronic stages of hypertension. The antihypertensive effect of MK-0521 was dose-dependent and persistent even after its cessation. Captopril also produced an antihypertensive effect, although the effect in the chronic stage of hypertension was less prominent than that in the acute stage of hypertension. MK-0521 was more inhibitory on the renin-angiotensin system than captopril. In the acute stage of hypertension, the dogs treated with MK-0521 had increased angiotensin converting enzyme (ACE) activity, while they had decreased plasma angiotensin II level and elevated plasma angiotensin I level and plasma renin activity. These results clarified the inhibitory effect of MK-0521 on ACE. In contrast, in the chronic stage of hypertension, MK-0521 showed no depression of plasma angiotensin II. There were no significant changes in daily urinary volume, and renal clearances of sodium, potassium and creatinine. These results suggest that the major mechanism of the antihypertensive effect of MK-0521 in 2-kidney Goldblatt hypertensive dogs is an inhibition of the ACE. In addition, the different effects in the acute and chronic hypertensive dogs suggest that some differences exist in the mechanisms of maintaining blood pressure between the two stages of 2-kidney Goldblatt hypertensive dogs.

Administration, Oral↗