Important role of serum proteins associated on the surface of particles in their hepatic disposition.

To elucidate the important factors for the difference in the hepatic disposition between polystyrene nanospheres with a size of 50 nm (NS-50) and lecithin-coated NS-50 (LNS-50), the liver perfusion studies and the in vitro uptake studies using the cultured Kupffer cells were performed. It was suggested that opsonin-mediated phagocytosis is not significantly involved in the hepatic disposition of LNS-50 in the presence of serum, whereas its involvement in the hepatic uptake of NS-50 was clearly demonstrated. Western blot analysis showed that IgG, complement C3, and fibronectin, well-known opsonins in the serum, adsorbed on the surface of NS-50 in larger amount than on the surface of LNS-50. On the other hand, serum albumin, which was suggested to function as a dysopsonin for the hepatic disposition of NS-50, was associated with both spheres almost to the same extent. These findings suggest that the hepatic disposition of LNS-50 at lower level should be ascribed to the less amount of serum opsonins associated on the surface and that the serum proteins associated with these spheres should be important as a determinant for their hepatic disposition.     

Surface hydrophobicity of particles is not necessarily the most important determinant in their in vivo disposition after intravenous administration in rats.

The in vivo disposition of polystyrene microsphere (MS) with the particle size of 50 nm (MS-50) and lecithin-coated MS-50 (LMS-50) after intravenous administration to rats was characterized. While a rapid elimination from the systemic circulation was observed for MS-50, much more prolonged circulating property was observed for LMS-50. In addition, this in vivo disposition property of LMS-50 was suggested to be ascribed to its lower affinity to the liver, which is the determining organ of the in vivo disposition of MS-50. The evaluation of surface hydrophobicity of MS-50 and LMS-50 in buffer solution revealed that the surface of MS-50 is more hydrophobic than that of LMS-50. However, LMS-50 was oppositely found to be more hydrophobic than that of MS-50 in rat serum. The profiles of serum proteins associated with MS-50 and LMS-50 were also examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The results showed that the amounts of some adsorbed proteins are greatly different between MS-50 and LMS-50. From these findings, it was suggested that the substantial difference in the in vivo disposition between MS-50 and LMS-50 would not be attributed to the difference in their surface hydrophobicity in the blood, but the difference in the type of serum proteins associated with them.     

Mechanisms of hepatic disposition of polystyrene microspheres in rats: effects of serum depend on the sizes of microspheres.

To study the mechanisms of the hepatic disposition of polystyrene microspheres (MS), effects of serum on their hepatic disposition characteristics were investigated for MSs with particle sizes of 50 nm (MS-50) and 500 nm (MS-500) by isolated liver perfusion experiments. It was revealed that serum in the perfusate inhibited and promoted the hepatic disposition of MS-50 and MS-500 at 37 degrees C, respectively. However, pre-heating at 56 degrees C or pre-treatment with anti-C3 antibody of serum reduced the promotive effect of serum on the hepatic uptake of MS-500, suggesting that the complement system should be involved as opsonins for the hepatic uptake of MS-500. Hepatic disposition of both MSs at 4 degrees C was reduced by the addition of serum into the perfusate, which could be ascribed to the reduction of the surface hydrophobicity of MSs due to the adsorption of serum proteins onto the surface of MSs and to resultant decrease in non-specific disposition to the liver. From these results, serum was found to function both as the opsonin to enhance the hepatic uptake of MSs and as the inhibitor by reducing non-specific interaction between MSs and the plasma membrane. Whether serum promotes or inhibits the hepatic disposition of MSs would be dependent on the particle sizes of MSs.     

Evaluation of route of input on the hepatic disposition of diazepam

Diazepam, a drug of high intrinsic clearance, was studied in the in situ rat liver dually perfused with Krebs-bicarbonate buffer containing human serum albumin (HSA; 0-1%) and unlabeled diazepam (1 mg/l) under constant hepatic arterial (3 ml/min) and portal venous (PV; 12 ml/min) flow rates. Events after a unit impulse (using [(14)C]diazepam) and at steady state (using unlabeled diazepam) were evaluated. In the absence of HSA the fractional effluent recovery (F) after hepatic arterial infusion (0.046 +/- 0.013) was about twice that after PV infusion (0.019 +/- 0.006). With HSA present, regardless of input route, F increased as unbound diazepam fraction in perfusate decreased (e.g., for PV, F = 0.58 +/- 0.05 and 0.69 +/- 0.02 for unbound diazepam fraction values of 0.18 +/- 0.01 and 0.037 +/- 0.01 at 0.25% and 1% HSA). The effluent [(14)C]diazepam profile was also dependent upon HSA. On decreasing HSA from 1 to 0.25% the early sharp peak (at 12-20 s) was replaced by a flatter unimodal profile with a later peak (at 60-80 s). Comparison of estimated effective permeability-surface area product to perfusate flow ratios (4.4 for 1% HSA and 21 for 0.25% HSA) indicated a shift from a perfusion rate-limited uptake with 0.25% HSA to one intermediate between permeability and perfusion at 1% HSA. Recognizing that orally absorbed drug enters the liver only via PV and i.v. drug via both vascular routes, this study emphasizes the difference in hepatic extraction of compounds depending on route of input, and the role that alteration in perfusate binding has on hepatic drug disposition.     

Pharmacokinetic analysis of in vivo disposition of succinylated proteins targeted to liver nonparenchymal cells via scavenger receptors: importance of molecular size and negative charge density for in vivo recognition by receptors

In vivo disposition characteristics of succinylated (Suc-) proteins were studied after intravenous injection in mice in relation to their molecular characteristics as negatively charged macromolecules. Recombinant superoxide dismutase (SOD; molecular mass, 32 kDa), bovine serum albumin (BSA; molecular mass, 67 kDa), and bovine IgG (molecular mass, 150 kDa) were used to produce succinylated derivatives with different degrees of modification. (111)In-labeled Suc-SODs were rapidly excreted into the urine with no significant hepatic uptake. In contrast, (111)In-Suc-BSA and Suc-IgG were significantly taken up by liver nonparenchymal cells via scavenger receptors (SRs) according to the degree of succinylation and the dose injected. Interestingly, highly succinylated BSAs exhibited significant accumulation in the kidney at higher doses when the hepatic uptake was saturated. Pharmacokinetic analysis demonstrated that the hepatic uptake of succinylated proteins depended on the molecular size and the estimated surface density of succinylated amino residues. Further analysis based on a physiological pharmacokinetic model, involving a saturable process with Michaelis-Menten kinetics, revealed that the surface density of negative charges was correlated with the affinity of larger succinylated proteins for the hepatic SRs. Thus, the present study has provided useful basic information for a therapeutic strategy and the molecular design of succinylated proteins for use as drug carriers and therapeutic agents per se for SR-mediated targeting in vivo.     

Elimination kinetics of circulating antigens and immune complexes. II. Hepatic and extrahepatic elimination of chemically modified albumin preparations in relation to their non-specific physicochemical properties

Formaldehyde-treated human serum albumin (fHSA) was analysed and compared with dinitrophenylated human serum albumin (DNP35HSA) with respect to net charge, hydrophobicity, and state of aggregation. The blood clearance and tissue distribution of intravenously injected fHSA was studied in mice. Similarly to DNP-HSA, fHSA was rapidly cleared from the blood stream owing to hepatic uptake and to extrahepatic deposition. We found no evidence supporting that fHSA was eliminated from the blood by hydrophobic interaction with cell or tissue surfaces. The blood clearance rate and the hepatic uptake of fHSA was not influenced by the presence of formylated peptides, indicating that receptors for formylated peptides were not involved in the handling of circulating fHSA.     

Studies on the biosynthesis of albumin and proteins in human liver tissue

Abstract. The incorporation rate of leucine into albumin and the incorporation rate of leucine into hepatic proteins were determined in human liver tissue slices.
Leucine was linearly incorporated into hepatic tissue albumin, into albumin released into the incubation medium, and into hepatic proteins during 4 h incubation. Amino acids stimulated the albumin and hepatic protein synthesis in vitro and in vivo . The incorporation rate of leucine into hepatic albumin and tissue proteins was correlated to hepatic RNA concentration.
In twenty-one experiments the mean incorporation rate of leucine into hepatic tissue immunoreactive albumin was 5.1±0.6 μmol leucine h^-1 g albumin^-1 (mean±; SEM), and 0.87±;0.17 μmol leucine h^-1 g albumin^-1 into albumin released to the incubation medium. By crossed immunoelectrophoresis, the hepatic immunoreactive albumin could be partly resolved into two components one of which migrated at the same rate and the other at a lower rate than serum albumin. Treatment of the slowly migrating component with a low concentration of trypsin changed its mobility to that of serum albumin. Gel filtration through Sephadex G-100 of the slowly migrating fraction showed that it had similar molecular size as that of serum albumin. The results support the hypothesis that human hepatic albumin biosynthesis involves a polypeptide precursor similar to that described for the rat liver.     

Determinants of hepatic function in liver cirrhosis in the rat. Multivariate analysis.

We investigated the determinants of hepatic clearance functions in a rat model of liver cirrhosis induced by phenobarbital/CCl4. Aminopyrine N-demethylation (ABT), galactose elimination (GBT), and serum bile acids (SBA) were determined in vivo. The livers were then characterized hemodynamically: intrahepatic shunting (IHS) was determined by microspheres and sinusoidal capillarization by measuring the extravascular albumin space (EVA) by a multiple indicator dilution technique. The intrinsic clearance was determined by assaying the activity of the rate-limiting enzymes in vitro. Hepatocellular volume (HCV) was measured by morphometry. ABT and SBA, but not GBT, differentiated cirrhotic from normal liver. IHS ranged from normal to 10%; all cirrhotic livers showed evidence of sinusoidal capillarization (reduced EVA). The cirrhotic livers showed a bimodal distribution of HCV, HCV being decreased in 50% of the cirrhotic livers. Multivariate analysis showed EVA and portal flow to be the main determinants of microsomal (ABT) and cytosolic (GBT) clearance function; SBA, by contrast, were determined solely by IHS. We conclude that sinusoidal capillarization is the main determinant of hepatic clearance, while serum bile acids reflect intrahepatic shunting. These findings emphasize the importance of alterations of hepatic nutritional flow to explain reduced clearance function in cirrhosis of the liver.     

Radioimmunoassay of glycosylated albumin with monoclonal antibody to glucitol-lysine

An immunoassay specific for glycosylated albumin was developed by the use of beads coated with antibody to human serum albumin (beads) and 125I-labelled monoclonal antibody to reduced bovine glucosylated low density lipoprotein. One bead was capable of binding 100 ng of serum albumin which had been treated with sodium borohydride (NaBH4) to reduce the Schiff base in the protein. The monoclonal antibody reaction with glucitol-lysine epitopes on the reduced glucosylated proteins and amino acids studied, including human serum albumin (HSA), bovine serum albumin and hippuryl-L-lysine. The detection limit of this assay was 100 pmol/mg HSA, which was sensitive enough for clinical use. The mean serum reduced glycosylated albumin concentration measured by this new method was significantly higher in diabetic patients (2.63 +/- 0.35 nmol/mg HSA, n = 32) than in healthy subjects (0.53 +/- 0.05 nmol/mg HSA, n = 38). The serum reduced glycosylated albumin concentration correlated with both hemoglobin A1c (r = 0.69, p less than 0.005) and the fasting blood glucose level (r = 0.51, p less than 0.005) in diabetic patients.     

Influence of acute viral hepatitis on phenytoin kinetics and protein binding.

Patients with liver disease are thought to have abnormal responses to drugs metabolized by the liver, although supportive evidence is sparse. The influence of acute viral hepatitis on the pharmacokinetics and protein binding of phenytoin (DPH) was examined in 5 patients. A longitudinal study design was used so that each patient acted as his own control. DPH clearance was unaffected by acute viral hepatitits over theconcentration range studie, but the percentage of unboudn DPH increased by an average of nearly one-third during acute viral hepatitis. A small decline in serum albumin concentration and elevated serum bilirubin levels may be responsible for the alterations in protein bindig. These results indicate that acute inflammatory liver disease has complex and perhaps paradoxical effects on durg disposition. Clinical and laboratory observations including plasma durg concentrations, still provide the best means for adjusting dosage regimens in patients with fluctuating hepatic function.     

Preparation and characterisation of rose Bengal-loaded surface-modified albumin nanoparticles.

Surface-modified albumin nanoparticles were prepared from two poly(ethylene glycol)-human serum albumin conjugates: poly(thioetheramido acid)-poly(ethylene glycol) copolymer-grafted HSA (HSA-PTAAC-PEG) and methoxy poly(ethylene glycol)-grafted HSA (HSA-mPEG). Rose bengal (RB) was used as a model drug for encapsulation into the nanoparticles either during the particle production or by adsorption post particle preparation. The drug incorporation and release was affected by the different production methods and the different polymer compositions. When RB was loaded in HSA and HSA/HSA-PTAAC-PEG nanoparticles, up to 5% (w/w) drug content was achieved. The drug loading in HSA-mPEG nanoparticles was much lower and the results from the microcalorimetry study indicated that the low loading efficiency was due to less drug-protein binding sites available in the HSA-mPEG molecule as compared to the HSA molecule. The release of RB from the albumin nanoparticles was very slow in PBS and dramatically accelerated in the presence of trypsin. Compared with unmodified nanoparticles, the slower release of RB from the surface-modified HSA nanoparticles in the presence of the enzyme suggested that the existence of a steric hydrophilic barrier on the surface of the nanoparticles made digestion of the nanoparticles more difficult.     

Cationic charge-dependent hepatic delivery of amidated serum albumin.

To obtain a quantitative correlation between the physicochemical properties of amidated bovine serum albumin (BSA) and their tissue distribution characteristics for the development of targeted delivery of proteins, BSA was amidated with hexamethylenediamine (HMD) or ethylenediamine (ED) to obtain cationized BSAs. Their structural changes were examined by spectroscopic and electrophoretic techniques then their tissue distribution was studied in mice. Circular dichroism (CD) and fluorescence measurements showed that spectroscopic changes occurred as the number of free NH2 groups increased. Capillary electrophoresis revealed a linear relationship between the mobility and the increased number of free NH2 groups. 111In-cationized BSAs were rapidly taken up by liver, but HMD-BSA showed a faster uptake than ED-BSA with a similar number of free NH2 groups, suggesting that the diamine reagent with a longer carboxyl side chain results in more efficient hepatic targeting. The hepatic uptake clearance (CL(liver)) of both derivatives increased significantly with a decrease in electrophoretic mobility (mu(ep)) towards the anode and reached a plateau at low electrophoretic mobility. The electrophoretic mobility is an appropriate indicator of the degree of amidation, which was closely correlated with the hepatic uptake clearance. The correlation between the mobility and the clearance shows that a low degree of amidation is sufficient for efficient hepatic targeting of proteins.     

Coordinate induction of both cytochrome P4503A and MDR1 by St John's wort in healthy subjects

BACKGROUND: Many drugs are cosubstrates of cytochrome P450 (CYP) 3A and MDR1; furthermore, their disposition is markedly affected by pretreatment with inducing agents, including St John's wort. Such drug interactions reflect induction of both proteins through a common mechanism involving the steroid X receptor/pregnane X receptor. However, the relative contributions of enhanced metabolism and efflux transport to the overall induction process are unknown. METHODS: The effects of 12 days' pretreatment with St John's wort on the disposition of selected in vivo probe drugs were determined in 21 young healthy subjects. Midazolam after oral and intravenous administration was used to assess CYP3A activity in both the intestinal epithelium and the liver, whereas the disposition of fexofenadine after an oral dose was assumed to be a measure of MDR1 function, and the oral plasma concentration-time profile of cyclosporine (INN, ciclosporin) was considered to reflect both CYP3A and MDR1 activities. RESULTS: St John's wort markedly affected the plasma concentration-time profiles of all of the drugs, with associated increases in their clearance. With midazolam, the enhancement was considerably less after intravenous administration (approximately 1.5-fold) than after oral administration (approximately 2.7-fold), and estimated intestinal and hepatic extraction ratios were higher by approximately 1.2- to 1.4-fold. By contrast, the oral clearances of fexofenadine and cyclosporine were equally increased by approximately 1.6-fold and 1.9-fold, respectively; these changes were both statistically less than for midazolam's oral clearance and greater than its estimated intestinal extraction. CONCLUSIONS: Although the disposition of all 3 drugs was altered by St John's wort, the extent of induction measured by oral clearance was different with CYP3A activity (midazolam), apparently increasing more than MDR1 function (fexofenadine), whereas with cyclosporine the change in oral clearance appeared to be more closely associated with the increase in MDR1 rather than CYP3A, despite the fact that both proteins are importantly involved in its disposition. These discordances indicate that, although a common molecular mechanism may be involved, the quantitative aspects of induction are complex and depend on the particular drug and the relative contributions of CYP3A and MDR1 in its disposition.     

Clearance of circulating IgA immune complexes is mediated by a specific receptor on Kupffer cells in mice

To characterize the physiology of circulating IgA immune complexes (IgA- IC), the dynamics of IgA-IC removal by the liver were examined. After intravenous injection, covalently cross-linked IgA antibodies to the dinitrophenyl determinant were rapidly removed from the circulation by the liver. Immunofluorescence microscopy and light and electron microscope autoradiography showed that the IgA-IC were associated with Kupffer cells. With increasing doses of injected IgA-IC the clearance velocity approached a maximum, thus prolonging the circulation of IgA- IC. All these observations indicated a receptor-mediated process. Saturating doses of various potential receptor-blocking agents, heat- aggregated mouse IgG, microaggregated human serum albumin, and purified dimeric IgA did not influence the clearance pattern and hepatic uptake of radiolabeled IgA-IC. Mouse livers were also perfused via the portal vein with 1 microgram of IgA-IC. In the presence or absence of serum proteins, 43% of the perfused IgA-IC were removed in a single passage. This liver uptake was not reduced with simultaneous perfusion of large doses of aggregated mouse IgG, aggregated human serum albumin, or purified free dimeric mouse IgA. In contrast, the liver uptake of radiolabeled IgA-IC was decreased by 88% with the addition of 1 mg unlabeled IgA-IC. These observations support the conclusion that removal of IgA-IC from circulation is mediated by a specific IgA receptor on Kupffer cells.     

A covalently linked recombinant albumin dimer is more rapidly cleared in vivo than are wild-type and mutant C34A albumin

Mammalian albumins are abundant plasma proteins that exhibit a relatively slow terminal clearance. For this reason they have been fused to potentially therapeutic proteins with rapid terminal clearance to produce fusion proteins with more desirable clearance profiles. A disulfide-linked albumin dimer has been described, but its abundance and stability in plasma are uncertain. To determine whether an obligatory albumin dimer incapable of dissociation would clear less rapidly than monomeric albumin, we expressed 3 recombinant rabbit serum albumin (RSA) polypeptides: H6RSA, RSA modified by the addition of an N-terminal hexahistidinyl tag; H6RSA(C34A), H6RSA with a single cysteine (Cys) 34-to-alanine (Ala) substitution (C34A); and DiRSA, H6RSA(C34A) joined by way of its C-terminus to RSA(C34A) through an intervening hexaglycine spacer. The C34A mutation was introduced to eliminate the possibility of disulfide bond-mediated dimerization. We expressed the proteins with the use of the yeast Pichia pastoris and purified them using nickel-chelate, ion exchange, and gel-filtration chromatography. After radioiodination and injection into rabbits, H6RSA and H6RSA(C34A) exhibited indistinguishable terminal catabolic half-lives (4.9 +/- 0.7 and 4.8 +/- 0.5 days, mean +/- SD), whereas that of DiRSA was reduced to 3.0 +/- 0.3 days (p<.05). The three proteins circulated in intact form, and their distributions in liver, lung, kidney, heart, and spleen did not differ 24 hours after injection. Although more DiRSA than H6RSA(C34A) was present in urine, in both cases it was in acid-soluble form. Ethyl palmitate treatment reduced the relative acceleration of DiRSA clearance compared with that of H6RSA(C34A), suggesting a role for the reticuloendothelial system in the differential clearance of the larger protein. Our results suggest that an albumin fusion protein should include only a single copy of albumin; that if the fusion protein exceeds a certain size, it may not acquire the slow clearance profile of native albumin; and that albumin dimerization through Cys34 probably does not contribute substantially to albumin metabolism in vivo.     

An in vitro assay based on surface plasmon resonance to predict the in vivo circulation kinetics of liposomes

The adsorption of blood proteins onto liposomes and other colloidal particles is an important process influencing the circulation time. Proteins adsorbed to the surface of liposomes can mediate recognition of the liposomes by macrophages of the reticuloendothelial system (RES) facilitating their clearance from the circulation. Coating liposomes with poly(ethylene glycol) (PEG) decreases the blood clearance considerably, most likely due to reduced protein adsorption and/or liposome aggregation. By using the relation between clearance and protein binding, the present study introduces an in vitro assay measuring interactions of liposomes with proteins to predict their blood clearance in vivo. Such assay is valuable since it limits time and costs, and importantly reduces the number of animals required for pharmacokinetic investigations of new formulations. In the current study, Surface Plasmon Resonance (SPR) and fluorescence Single Particle Tracking (fSPT) were used to study liposome–protein interactions and blood induced liposome aggregation in vitro. By means of SPR the interactions between proteins and liposomes coated with PEG of different molecular weights and at different densities (PEG₂₀₀₀ in 2.5%, 5% and 7%; PEG₅₀₀₀ in 0.5%, 1.5% and 2.5%), were measured for several plasma proteins: human serum albumin (HSA), apolipoprotein E (ApoE), α2-macroglobulin (α2-M), β2-glycoprotein (β2-G) and fibronectin (Fn). Liposomes coated with PEG interacted less with all proteins, an effect which increased with the PEG surface density. In parallel, fSPT analysis showed that the exposure of liposomes to full blood did not change the liposome size, indicating that aggregation is not a strong attributive factor in the clearance of these liposomes. In addition, the SPR measurements of the interactions between liposomes and proteins were correlated with the blood clearance of the liposomes. For each protein, the degree of protein–liposome interaction as determined by SPR showed a moderate to strong positive correlation with the clearance of the liposome type.     

In vitro analysis of human drug glucuronidation and prediction of in vivo metabolic clearance

The glucuronidation of a number of commonly used hepatic uridine diphosphate glucuronosyltransferase drug substrates has been studied in human tissue microsomes. Prediction of in vivo hepatic drug glucuronidation from liver microsomal data yielded a consistent 10-fold under-prediction. Consideration of protein binding was observed to be pivotal when predicting in vivo glucuronidation for acid substrates. Studies using human intestinal microsomes demonstrated the majority of drugs to be extensively glucuronidated such that the intrinsic clearance (CL(int)) of ethinylestradiol (CL(int) = 1.3 microl/min/mg) was twice that obtained using human liver microsomes (CL(int) = 0.7 microl/min/mg). The potential extrahepatic in vivo glucuronidation was calculated for a range of drug substrates from human microsomal data. These results indicate the contribution of intestinal drug glucuronidation to systemic drug clearance to be much less than either hepatic or renal glucuronidation. Therefore, data obtained with intestinal microsomes may be misleading in the assessment of the contribution of this organ to systemic glucuronidation. The use of hepatocytes to assess metabolic stability for drugs predominantly metabolized by glucuronidation was also investigated. Metabolic clearances for a range of drugs obtained using fresh preparations of human hepatocytes predicted accurately hepatic clearance reported in vivo. The use of cryopreserved hepatocytes as an in vitro tool to predict in vivo metabolism was also assessed with an excellent correlation obtained for a number of extensively glucuronidated drugs (R(2) = 0.80, p < 0.001).     

The clearance of antipyrine and indocyanine green in normal subjects and in patients with chronic lever disease.

The pharmacokinetics after oral administration of 1,200 mg antipyrine and intravenous administration of 0.5 mg/kg indocyanine green have been investigated in 6 normal subjects and in 20 patients with chronic liver disease of varying etiology. Severe impairment of liver function associated with a decrease in serum albumin, elevation in serum bilirubin, or prolongation in prothrombin time correlated with a fall in the clearance of both drugs. The clearance of the two drugs correlated well in normal subjects and in patients with chronic liver disease. The presence of a surgical portacaval anastomosis was associated with a lower indocyanine green clearance for comparable clearance of antipyrine. The concept of functioning hepatic parenchymal mass is proposed as a common rate-limiting parameter for the elimination of the two drugs.     

Reduced hepatic clearance of propranolol induced by chronic carbon tetrachloride treatment in rats

Effect of liver injury induced by chronic treatment with carbon tetrachloride for 1 to 4 months on hepatic clearance of propranolol was investigated in male Wistar rats. Plasma propranolol level after i.v. and p.o. dosing (1.0 mg/kg) was always higher in the rats which were treated for 2 and 4 months than in control (sham-injected) rats. The chronic treatment reduced hepatic clearance of propranolol significantly, yielding only approximately 30 to 50% of the control clearance value. Distribution volume of this drug was also significantly reduced by the chronic treatment but seemed to be less sensitive to the treatment than the hepatic clearance. Accordingly, the elimination rate constant was decreased slightly in the rats treated longer than 2 months. The chronic treatment for 2 and 4 months also reduced intrinsic hepatic clearance substantially. The hepatic clearance estimated for both these control and chronically treated rats was significantly dependent on the liver blood flow. Furthermore, propranolol was eliminated much more slowly in the injured liver of the rat which was treated for 2 or 4 months than in the control liver when perfused in in vitro technique. It is, therefore, suggested that the metabolic dysfunction induced by chronic treatment with carbon tetrachloride may be directly related to substantial changes in anatomical arrangement of the hepatic circulation (portasystemic shunting), which may be due to a fibrosis of the tissue.     

Clearance of antipyrine-dependence of quantitative liver function

Abstract. The purpose of the present study was to assess the influence of liver disease on the hepatic drug-metabolizing enzyme systems. The clearance of antipyrine was found to be significantly decreased in 13 patients with liver disease compared with 9 control patients (18.5 and 58.6 ml/min. respectively). Among the patients with liver disease, those with a severely reduced capacity for work had significantly lower clearance of antipyrine than non incapacitated patients (12.5 and 25.4 ml/min. respectively). The clearance of antipyrine was significantly correlated with the galactose elimination capacity, the serum albumin and the prothrombin values. The results indicate that the drug-metabolizing capacity of the liver changes in parallel with the other metabolic functions, and the use of the clearance of antipyrine as a quantitative test of liver function is suggested.