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Biomedical subjects

M Hanano

Publications and source records attributed to M Hanano.

At least 181 records · Page 10Linked to original sources

Saturable transport of cimetidine from cerebrospinal fluid to blood in rats.

Cimetidine, a histamine H2 receptor antagonist, is known to have some effects on central nervous system, and is reported to emerge in the cerebrospinal fluid (CSF). We evaluated the elimination of cimetidine from CSF by the method of ventriculo-cisternal perfusion in rats. The extraction ratio of cimetidine at the low perfusate concentration (14 nM) was 0.190 +/- 0.023 (n = 3), while that significantly (p less than 0.02) decreased to 0.0916 +/- 0.081 (n = 3) at the high concentration (4 mM). No significant difference was observed in the production rate of CSF between these two concentrations. These findings suggest that cimetidine is excreted from CSF to blood by a saturable transport system.

Animals↗

Prediction of the plasma concentration time courses of various drugs in humans based on data from rats.

The concentrations of seven drugs, i.e., phenobarbital (PB), phenytoin (DPH), hexobarbital (HXB), quinidine (QD), tolbutamide (TB), valproate (VA), and diazepam (DZP) in human plasma were predicted by a physiologically-based pharmacokinetic model using the intrinsic clearance of unbound drug and the tissue-to-plasma unbound concentration ratios extrapolated from rat data, and the plasma protein binding, blood-to-plasma concentration ratios and physiological parameters in humans. The predicted concentration curves of DPH, HXB, QD and PB in human plasma showed comparatively good agreements with the observed values except for TB, VA and DZP, for which the area under concentration-time curves (AUC) were overestimated or underestimated.

Animals↗

Permeability of materials in postglomerular capillary bed and distribution to interstitium of kidney in rats.

Extracellular reference materials are necessary to estimate tubular transport parameters for drugs which are secreted in the kidney. They must set up the flow-limited distribution between plasma and interstitial space, not be distributed to the intracellular space, and be nondegradable in the extracellular space. The capillary permeability of various molecular weight markers in the post glomerular circulation was investigated by performing pulse-injection multiple indicator dilution experiments on isolated rat kidney, using simultaneous injection of T1824-labeled albumin (the plasma reference) and creatinine (or inulin) as the extracellular reference materials. The permeability constants and the gamma values (ratio of the volume in the space of interstitium to that of capillary plasma) for creatinine and inulin were calculated by a nonlinear least squares regression. The gamma values for creatinine were greater than those for inulin, implying that the volume of distribution for creatinine is different from that for inulin. The capillary permeability clearance (CLinflux) for creatinine was 4 times higher than that of inulin, and was 3 times greater than the perfusion rate. Thus, creatinine satisfies the qualification for the flow-limited distribution between plasma and interstitial space. These findings suggest that in the rat kidney creatinine is more suitable for the extracellular reference material than inulin.

Animals↗

Pharmacokinetic study on the hepatic uptake of indocyanine green in cirrhotic patients.

The mechanism by which the mean blood clearance (CLtot,B) of indocyanine green (ICG) was reduced in cirrhotic patients was examined pharmacokinetically. It was demonstrated that the reduction in the CLtot,B of ICG in cirrhosis would be mainly due to the decrease in the hepatic uptake clearance and partly due to the increase in the efflux clearance from the liver to plasma. It is suggested that the decrease in the hepatic uptake clearance in cirrhosis mainly reflects the decrease in the intrinsic clearance of hepatic uptake rather than the decrease in hepatic blood flow.

Adult↗

Hepatic extraction of chenodeoxycholic acid in dogs chronically intoxicated with dimethylnitrosamine.

The pharmacokinetics of chenodeoxycholic acid (CDCA) in hepatic dysfunction were evaluated by analyzing the plasma disappearance curves after simultaneous administration of [3H]- and [14C]-CDCA through the femoral and portal veins, respectively, in dogs chronically intoxicated with dimethylnitrosamine (DMN). The plasma concentration-time curve of intravenously administered [3H]-CDCA was best fitted to a three-exponential equation, while that of intraportally administered [14C]-CDCA was fitted to either a two- or a three-exponential equation. In the DMN-intoxicated dogs, significant decreases were observed in total body plasma clearance (CLp), hepatic extraction ratio (EH) and apparent intrinsic clearance (CLint) compared to those of the untreated (control) dogs. The hepatic blood flow (QH), calculated from CLp, CLint and blood-to-plasma concentration ratio (RB) according to the equation reported by Wilkinson and Shand [Clin. Pharmac. Ther. 18, 377 (1975)], was reduced to approximately 70% in the DMN-intoxicated dogs compared to the control dogs. The bindings of CDCA to plasma and liver cytosol fraction were determined by equilibrium dialysis; no significant difference was observed in the unbound fraction between the DMN-treated and control dogs. By comparing both pharmacokinetic parameters obtained from intravenous and intraportal administration, the usefulness of the oral bile acid tolerance test was examined. From these findings, it was suggested that the decrease in the CLp of the DMN-intoxicated dogs was due to both the decrease in QH and that in CLint, and that the decrease in CLint may be due not to an alteration of plasma or cytosol binding but to that of a carrier-mediated transport system. It is also suggested that the measurement of fasting plasma bile acid concentration or the oral bile acid tolerance test is more sensitive for the detection of hepatic dysfunction than the intravenous bile acid tolerance test.

Animals↗

Hepatic transport of indocyanine green in dogs chronically intoxicated with dimethylnitrosamine.

Hepatic transport of indocyanine green (ICG) was examined in dogs chronically intoxicated with dimethylnitrosamine (DMN) (2 mg/kg) intraportally once a week for 6 weeks. In pathophysiological consequences, significant increases (p less than 0.05) were shown in both glutamic-pyruvic transaminase (GPT) and total plasma bile acids, but no significant difference was shown in body weight, liver wet weight, glutamic-oxaloacetic transaminase (GOT), plasma alkaline phosphatase activity, total plasma protein, and total plasma bilirubin. By histologic examination of livers from intoxicated dogs, increased fibrosis in periportal, perisinusoidal, and especially pericentral areas, with loss of normal architecture, was observed. Partial fibrous bridging between periportal and pericentral areas was also demonstrated, but extensive pseudolobulation with regenerative nodules was not observed. The portal venous pressure of the intoxicated dogs was increased by approximately 50% of that of control dogs. In intoxicated dogs, delays were shown in both plasma disappearance and biliary excretion of ICG and significant decreases were observed in the pharmacokinetic parameters k12 (plasma to liver transfer rate constant), V2 (distribution volume of liver compartment), and CLtot (total body-plasma clearance), while a significant increase was observed in k23 (intrahepatic diffusion and transport rate constant); the V1 (distribution volume of plasma compartment) was not altered. From these findings, it is suggested that the decrease in the intrinsic clearance of ICG for the hepatic uptake process might explain the decrease in ICG uptake rate into the liver which was observed in the DMN-intoxicated dogs. Dogs chronically intoxicated with DMN might be a good model for studying hepatic dysfunction.

Alanine Transaminase↗

Pharmacokinetic study of exogenously administered beta-endorphin using a rapid radioreceptor assay in rats.

A rapid radioreceptor assay for measuring beta-endorphin (beta-EP) in unextracted serum has been developed. The method is based upon the inhibition by beta-EP of 3H-naloxone binding to the specific receptors on rat brain membranes, prepared in a stable form of pellets. Effect of serum on the assay was minimized by adding pooled serum to the equal dilution of total serum in the assay mixture. Pharmacokinetic analysis of pharmacologically active beta-EP equivalents (beta-EP eq.) in rats was performed using this method. The serum disappearance of beta-EP eq. after iv administration followed a biexponential decline and pharmacokinetic parameters were calculated by a two-compartment open model. The half-lives of alpha-phase and beta-phase were 2.6 +/- 0.5 min and 6.2 +/- 1.6 hr (mean +/- SE; n = 6), respectively. The volume of the central compartment (V1) and that of steady-state (Vdss) were 67 +/- 16 and 480 +/- 75 ml/kg (mean +/- SE; n = 6), respectively. The total body serum clearance (CLtot) was 2.1 +/- 0.9 ml/min/kg (mean +/- SE; n = 6). The serum disappearance curve of beta-EP eq. obtained in the present study was similar to that previously reported by Houghten et al. (Proc. Natl. Acad. Sci. U.S.A. 77, 4588-4591 (1980) ), in which the disappearance of total radioactivity of tritiated beta-EP in rats was examined.

Animals↗

Use of the fluorescence probe 1-anilino-8-naphthalenesulfonate in predicting interindividual differences in the plasma protein binding of acidic drugs in rats.

The possibility that the fluorescence probe, 1-anilino-8-naphthalenesulfonate (I), might be used for predicting the interindividual differences in the plasma protein binding of acidic drugs was examined. The interindividual differences in the free fraction of I (fI) were found not to be due to corresponding differences in plasma albumin concentration, but to those differences in binding constant. The binding constant of I to the plasma of 18 individual rats ranged from 1.75 X 10(6) M-1 to 2.3 X 10(7) M-1. The free fraction of I had a highly significant statistical correlation with plasma concentration of free fatty acids, but had no significant correlation with the infinite fluorescence of I or the degree of the polarization of I. Each free fraction of five acidic drugs (warfarin, phenylbutazone, salicylic acid, indomethacin, and sulfaphenazole ) was correlated with fI with high statistical significance. Therefore, the simple and convenient method using I may predict the interindividual differences in the plasma protein binding of acidic drugs in rats.

Acids↗

Interaction of doxorubicin with nuclei isolated from rat liver and kidney.

The interaction of doxorubicin with nuclei isolated from rat liver and kidney was studied by fluorospectrometry . The nuclei had at least two different types of binding sites for the drug. Both Mg2+ and Ca2+ competitively inhibited the binding of doxorubicin to the nuclei, which showed a remarkable temperature dependency. No significant difference was observed between the numbers of binding sites (n = 6.70 X 10(-2) mol/mol of DNA for liver; 6.41 X 10(-2) mol/mol of DNA for kidney) or the affinity constants (Ka = 4.85 X 10(5) M-1 for liver; 5.41 X 10(5) M-1 for kidney) under quasi-physiological conditions. These results obtained from in vitro binding experiments support previous suggestions that the differences in the in vivo distribution of doxorubicin among tissues are not due to differences in the nuclear binding of the drug. The amount of nuclei per gram of tissue is the primary determinant of the characteristic tissue distribution of doxorubicin.

Animals↗

Effect of sulfaphenazole on tolbutamide distribution in rabbits: analysis of interspecies differences in tissue distribution of tolbutamide.

The effect of sulfaphenazole on the distribution of tolbutamide was examined by comparing the change in the steady-state volume of distribution (Vdss) determined from in vivo plasma elimination with the tissue-to-plasma concentration ratio of various tissues (Kp) in rabbits; this effect was compared with that previously reported in rats. In rabbits, the Kp values of six tissues studied (i.e., brain, heart, spleen, small intestine, muscle, and skin) increased in the presence of sulfaphenazole ; except for brain, lung, and adipose tissue, the tissue-to-plasma unbound concentration ratio (Kp,f) of other tissues did show a significant decrease. This suggested that both the tissue and plasma protein binding of tolbutamide were affected by sulfaphenazole and that the increase in Kp was due mainly to the displacement of plasma protein binding of tolbutamide by sulfaphenazole , which was greater than that of tissue binding, while no change in Kp was due to a parallel change in both the plasma protein binding and tissue binding of tolbutamide. In both rabbits and rats, the Vdss calculated from plasma concentration versus time curve was very close to that calculated from the Kp values and volumes of various tissues in the presence and absence of sulfaphenazole , respectively. The interspecies difference of the effect of sulfaphenazole on the tissue distribution of tolbutamide between rabbits and rats was elucidated from both in vivo tissue distribution and in vitro plasma protein binding studies.

Animals↗

In vitro and in vivo assessment of hepatic and extrahepatic metabolism of diazepam in the rat.

Since diazepam is metabolized by many organs in the rat, the microsomal fractions of the liver, kidney, and lung from male Wistar rats were assayed for NADPH-dependent metabolism of diazepam and enzymatic parameters. The predicted extraction ratios were obtained from this in vitro experimental system. The organ clearances of the liver, kidney, and lung were then calculated for the determination of the relative contribution of each eliminating organ to the total body clearance (CLtot) of diazepam in the rat. The liver was the most effective eliminating organ, followed by the kidney and the lung, in that order. The hepatic extraction ratio of diazepam was determined in vivo after portal and femoral vein administrations of diazepam. The validity of the in vitro experimental system for the liver was demonstrated by a good agreement between the calculated hepatic extraction ratio of diazepam from in vitro enzymatic parameters (0.616) and that derived in vivo (0.648). However, the sum of organ clearances of the liver, kidney, and lung did not account for CLtot of diazepam in the rat, suggesting the possible contribution of the metabolism in the other organs or tissues, or an underestimation of the pulmonary and renal metabolism.

Animals↗

Pharmacokinetic study on the mechanism of tissue distribution of doxorubicin: interorgan and interspecies variation of tissue-to-plasma partition coefficients in rats, rabbits, and guinea pigs.

The mechanism of interorgan and interspecies variations in the tissue distribution of doxorubicin was studied in rats, rabbits, and guinea pigs. The permeation properties of doxorubicin were investigated by using isolated rat erythrocytes as a model membrane. A significant dependency of the uptake rate constant on medium pH was observed, suggesting that only un-ionized doxorubicin is diffusible through the plasma membrane. The values of plasma unbound fraction (fp) of doxorubicin were 0.344 for rats, 0.415 for rabbits, and 0.529 for guinea pigs. The tissue DNA concentrations of rats were larger than those of rabbits and smaller than those of guinea pigs in corresponding organs or tissues. An in vitro organ model that described the distribution behavior of doxorubicin in the whole body was constructed, and an equation was derived to estimate the tissue-to-plasma partition coefficients, (Kp) from in vitro experiments. The in vitro Kp values showed comparatively good agreement with the in vivo Kp values for the various organs or tissues in all three species. Doxorubicin is exclusively bound to the nuclei in the cells. The variation of the Kp values in different organs depended on the amount of nuclei per gram of tissue. The primary determinant of the interspecies variation in the Kp values was the difference in tissue DNA concentrations among rats, rabbits, and guinea pigs, and a secondary determinant was the difference in fp values.

Animals↗

Prediction of the volumes of distribution of basic drugs in humans based on data from animals.

The apparent volume of distribution-after distribution equilibrium and the ratio of distributive tissue volume to the unbound fraction in the tissue (VT/fuT) of 10 weak basic drugs, i.e., chlorpromazine, imipramine, propranolol, disopyramide, lidocaine, quinidine, meperidine, pentazocine, chlorpheniramine, and methacyclin were compared in animal species and humans. In these two parameters, a statistically significant correlation between animals and humans was obtained, when the parameters were plotted on a log-log scale. The correlation coefficient between VT/fuT was significantly higher than that between the apparent volumes of distribution (p less than 0.05). In general, there was little difference between VT/fuT of various basic drugs in animals and that in humans. Prediction of the apparent volume of distribution in humans using animal data of VT/fuT, plasma unbound fraction, blood volume, and blood-to-plasma concentration ratio in humans was successful for most of drugs studied.

Animals↗

Prediction of the disposition of beta-lactam antibiotics in humans from pharmacokinetic parameters in animals.

Various pharmacokinetic parameters (disposition half-life, total body clearance, renal clearance, hepatic clearance, volume of distribution, intrinsic clearance and volume of distribution of unbound drug) of six beta-lactam antibiotics were compared in mouse, rat, rabbit, dog, monkey, and human. Two methods for prediction of the disposition of the beta-lactam antibiotics in humans by extrapolation of the animal data were evaluated. One was the Adolph-Dedrick approach, which can be used to predict clearances in humans from the relationship between intrinsic clearances and body weight in the other five species. The volume of distribution in humans was predicted from the relationship between the volume of distribution and serum unbound fraction in the five species. The other was the Boxenbaum approach, which can be used to predict the pharmacokinetic parameters of the six beta-lactam antibiotics in humans by using the regression lines of log-log plots of intrinsic clearance and volume of distribution of unbound drug in a single species, in this case the monkey. The half-life calculated according to the latter method had a smaller absolute error than that calculated according to the former method, but the better method for extrapolation of animal data to humans seems to be the former method, which does not require a priori information regarding structure-pharmacokinetic relationships among the antibiotics.

Animals↗

Estimation of renal secretory function for organic cations by endogenous N1-methylnicotinamide in rats with experimental renal failure.

To assess whether the secretory clearance of N1-methylnicotinamide (NMN), an endogenous organic cation, represents renal tubular secretion of the organic cation, the relationship between the secretory clearance of NMN, CLscn(NMN), and that of tetraethylammonium bromide (TEA), CLscn(TEA), was examined in normal and experimental renal failure (ERF) rats. TEA was selected as a representative organic cation secreted by the kidney. ERF was induced by glycerol, folate, salicylate, uranium, and gentamicin, substances which have been demonstrated to produce specific damage to the kidney by pathophysiological studies. Glomerular filtration rate (GFR), CLscn(NMN), and CLscn(TEA) decreased significantly in most of ERF rats, while blood urea nitrogen (BUN) increased significantly in all ERF rats. There was a statistically significant correlation (r = 0.952, p less than 0.001) between the endogenous CLscn(NMN) and CLscn(TEA) in both the normal and ERF rats. Correlation analysis revealed that CLscn(NMN) was superior to GFR in the degree of relationship to CLscn(TEA), but BUN could not be used as an index for the secretion of NMN or TEA. Although the plasma concentration of NMN in most of the ERF rats was much higher than that in the normal rats, it affected neither the urinary clearance of NMN itself nor the excretion of TEA. From these findings, we propose that CLscn(NMN) can be used as an index to assess renal tubular function for the secretion of organic cations that are excreted by both filtration and secretion without reabsorption.

Acute Kidney Injury↗

Effect of late pregnancy on salicylate, diazepam, warfarin, and propranolol binding: use of fluorescent probes.

Serum protein binding was measured in six women 38 wk pregnant and in five control subjects. Three distinct binding sites for drugs on human serum albumin have been identified. To determine whether changes in binding during pregnancy occur for common drugs or only for drugs that bind to a specific binding site, serum protein binding of three drugs--diazepam (site I), warfarin (site III), and salicylate--and four fluorescent probes--dansylsarcosine (site I), 1-anilino-8-naphthalenesulfonate (site I), 7-anilinocoumarin-4-acetic acid (site II), and 5-dimethylaminonaphthalene-1-sulfonamide (DNSA) (site III)--were determined in control and pregnant sera. Unbound fractions of diazepam and salicylate in pregnant women increased but the unbound fraction of warfarin did not change. Dissociation constants (Kd1) of all fluorescent probes but DNSA were almost the same in control and pregnant sera, while the Kd1 of DNSA in pregnant serum was approximately 50% of control. Binding capacities of all probes decreased, which was attributed to decreased serum albumin concentration. We concluded that serum protein binding of drugs that bind to site I or site II on albumin decreased largely because of the reduced serum albumin concentration during pregnancy and that the binding of drugs that bind to site III changed little because of compensating effects of the decrease in serum albumin concentration and the increase in binding affinity to serum albumin. Serum concentration of alpha 1-acid glycoprotein and serum binding of propranolol did not change in pregnant women.

Adult↗