Quantitative tests of liver function measure hepatic improvement after sustained virological response: results from the HALT-C trial.

BACKGROUND: The impact of virologic response on hepatic function has not been previously defined. AIM: To determine the relationships of quantitative liver function tests (QLFTs) with virological responses to peginterferon (PEG) +/- ribavirin (RBV) in patients with chronic hepatitis C and to use serial QLFTs to define the spectrum of hepatic improvement after sustained virological response (SVR). METHODS: Participants (n = 232) were enrolled in the Hepatitis C Antiviral Long-term Treatment against Cirrhosis (HALT-C) Trial, had failed prior therapy, had bridging fibrosis or cirrhosis and were retreated with PEG/RBV. All 232 patients had baseline QLFTs; 24 patients with SVR and 68 nonresponders had serial QLFTs. Lidocaine, [24-(13)C]cholate, galactose and (99m)Tc-sulfur colloid were administered intravenously; [2,2,4,2-(2)H]cholate, [1-(13)C]methionine, caffeine and antipyrine were administered orally. Clearances (Cl), breath (13)CO(2), monoethylglycylxylidide (MEGX), perfused hepatic mass (PHM) and liver volume were measured. RESULTS: Rates of SVR were 18-26% in patients with good function by QLFTs, but < or =6% in patients with poor function. Hepatic metabolism, measured by caffeine k(elim) (P = 0.02), antipyrine k(elim) (P = 0.05) and antipyrine Cl (P = 0.02) and the portal circulation, measured by cholate Cl(oral) (P = 0.0002) and cholate shunt (P = 0.0003) and PHM (P = 0.03) improved after SVR. CONCLUSION: Hepatic dysfunction impairs the virological response to PEG/RBV. SVR improves hepatic metabolism, the portal circulation and PHM.

The spectrum of hepatic functional impairment in compensated chronic hepatitis C: results from the Hepatitis C Anti-viral Long-term Treatment against Cirrhosis Trial.

BACKGROUND: The spectrum of functional impairment in patients with compensated chronic hepatitis C is incompletely defined. AIM: To define hepatic impairment by quantitative tests (quantitative liver function tests) and correlate results with disease severity in patients with chronic hepatitis C. METHODS: We studied 285 adult patients with chronic hepatitis C prior to treatment in the Hepatitis C Anti-viral Long-term Treatment against Cirrhosis Trial; 171 had Ishak fibrosis stages 2-4 (fibrosis) and 114 had stage 5 or 6 (cirrhosis). None had had clinical decompensation. A battery of 12 quantitative liver function test assessed the spectrum of hepatic microsomal, mitochondrial and cytosolic functions, and hepatic and portal blood flow. RESULTS: Twenty-six to 63% of patients with fibrosis and 45-89% with cirrhosis had hepatic impairment by quantitative liver function test; patients with cirrhosis had the greatest impairment (P-value ranging from 0.15 to <0.0001). Cholate Cl(oral), cholate shunt and perfused hepatic mass correlated with cirrhosis, stage of fibrosis (r = -0.51, +0.49, -0.51), varices and variceal size (r = -0.39, +0.36, -0.41). PHM < 95 and cholate shunt >35% identified 91% of patients with medium- or large-sized varices. CONCLUSIONS: Hepatic impairment is common in compensated patients with fibrosis or cirrhosis because of chronic hepatitis C. Cholate shunt, and cholate Cl(oral) and perfused hepatic mass, identify patients at risk for cirrhosis or varices.

Portal-systemic shunting in patients with fibrosis or cirrhosis due to chronic hepatitis C: the minimal model for measuring cholate clearances and shunt.

BACKGROUND: Measurement of portal inflow and portal-systemic shunt using cholate clearances could be useful in monitoring patients with liver disease. AIM: To examine relationships of cholate clearances and shunt to cirrhosis and varices and to define minimal sampling requirements. METHODS: Five hundred forty-eight studies were performed in 282 patients enrolled in the Hepatitis C Antiviral Long-term Treatment to prevent Cirrhosis (HALT-C) trial. Stable, non-radioactive isotopes of cholate were administered intravenously and orally, clearances (Cl(iv) and Cl(oral)) were calculated from [dose/area under curve (AUC)] and cholate shunt from [(AUC(oral):AUC(iv)) x (Dose(iv):Dose(oral)) x 100%]. RESULTS: Cholate Cl(oral) and cholate shunt correlated with prevalences of both cirrhosis and varices (P < 0.0001 for all). Peripheral venous sampling at 5, 20, 45, 60 and 90 min defined the minimal model. Linear regression of cholate shunt determined from five points within 90 min vs. the standard method of 14 points over 3 h yielded slope of 1.0 and intercept 0.5% (r(2) = 0.98, P < 0.0001). Results were identical in the 189 validation studies (slope 1.0, intercept 0.5%, r(2) = 0.99, P < 0.0001). CONCLUSIONS: Cholate Cl(oral) and cholate shunt may be useful in monitoring patients with liver disease. The 5-point model enhances application of cholate Cl(oral) and cholate shunt in the non-invasive assessment of the portal circulation.

Sepsis in cirrhosis: report on the 7th meeting of the International Ascites Club.

Sepsis is a systemic inflammatory response to the presence of infection, mediated via the production of many cytokines, including tumour necrosis factor (TNF-), interleukin (IL)-6, and IL-1, which cause changes in the circulation and in the coagulation cascade. There is stagnation of blood flow and poor oxygenation, subclinical coagulopathy with elevated D-dimers, and increased production of superoxide from nitric oxide synthase. All of these changes favour endothelial apoptosis and necrosis as well as increased oxidant stress. Reduced levels of activated protein C, which is normally anti-inflammatory and antiapoptotic, can lead to further tissue injury. Cirrhotic patients are particularly susceptible to bacterial infections because of increased bacterial translocation, possibly related to liver dysfunction and reduced reticuloendothelial function. Sepsis ensues when there is overactivation of pathways involved in the development of the sepsis syndrome, associated with complications such as renal failure, encephalopathy, gastrointestinal bleed, and shock with decreased survival. Thus the treating physician needs to be vigilant in diagnosing and treating bacterial infections in cirrhosis early, in order to prevent the development and downward spiral of the sepsis syndrome. Recent advances in management strategies of infections in cirrhosis have helped to improve the prognosis of these patients. These include the use of prophylactic antibiotics in patients with gastrointestinal bleed to prevent infection and the use of albumin in patients with spontaneous bacterial peritonitis to reduce the incidence of renal impairment. The use of antibiotics has to be judicious, as their indiscriminate use can lead to antibiotic resistance with potentially disastrous consequences.

A randomized, double-blind trial comparing pegylated interferon alfa-2b to interferon alfa-2b as initial treatment for chronic hepatitis C.

This international, randomized, active-controlled, parallel-group, double-blind dose-finding study compared peginterferon alfa-2b (PegIntron) to interferon alfa-2b for the initial treatment of compensated chronic hepatitis C. We randomly assigned 1,219 subjects to receive either the standard three-times-weekly (TIW) interferon alfa-2b dose (3 MIU) or the once-weekly (QW) peginterferon alfa-2b (0.5, 1.0, or 1.5 microg/kg). Subjects were treated for 48 weeks and then followed for an additional 24 weeks. All 3 peginterferon alfa-2b doses significantly (P < or =.042) improved virologic response rates (loss of detectable serum HCV RNA) after treatment and after follow-up, as compared with interferon alfa-2b. Unlike the end-of-treatment virologic response, the sustained virologic response rate was not dose-related above 1.0 microg/kg peginterferon alfa-2b because of a higher relapse rate among patients treated with 1.5 microg/kg peginterferon alfa-2b, particularly among patients infected with genotype 1. All 3 peginterferon alfa-2b doses decreased liver inflammation to a greater extent than did interferon alfa-2b, particularly in subjects with sustained responses. No new adverse events were reported, and the majority of adverse events and changes in laboratory values were mild or moderate. In conclusion, peginterferon alfa-2b maintained (0.5 microg/kg) or surpassed (1.0, 1.5 microg/kg) the clinical efficacy of interferon alfa-2b while preserving its safety profile. The higher rate of virologic response during treatment with 1.5 microg/kg peginterferon alfa-2b in patients infected with genotype 1 and high viral levels warrants further evaluation.

Biochemical and viral response to consensus interferon (CIFN) therapy in chronic hepatitis C patients: effect of baseline viral concentration. Consensus Interferon Study Group.

OBJECTIVE: The effect of baseline viral concentration on response was assessed as part of a multicenter phase 3 trial evaluating the safety and efficacy of CIFN therapy for chronic HCV infection. METHODS: Patients (n = 472) received either CIFN 9 microg or IFN alpha-2b 3 MU subcutaneously t.i.w. for 24 wk, followed by 24 wk of observation. RESULTS: Efficacy was assessed by the percentage of patients who achieved normal ALT values or undetectable HCV RNA values (using RT-PCR with a sensitivity of 100 copies/ml). There was a clear relationship between baseline viral concentration and either ALT or HCV RNA response; patients with lower titer HCV RNA had better response rates. End-of-treatment HCV RNA responses were better for patients with low viral concentrations treated with CIFN (51%) than for patients treated with IFN a-2b (31%) (p = 0.03). ALT responses in patients with low viral concentrations were 60% for CIFN-treated patients and 27% for IFN alpha-2b-treated patients (p < 0.01) at the end of treatment. Patients with high titer HCV RNA were more likely to have a sustained HCV RNA response after treatment with CIFN 9 microg, compared with those treated with IFN alpha-2b (7% vs 0%, p = 0.03). CONCLUSIONS: Both genotype and baseline viral concentration were independent factors that affected response to interferon.

A novel, simple method of functional spleen volume calculation by liver-spleen scan.

UNLABELLED: Spleen enlargement is commonly associated with portal hypertension from cirrhosis and may cause thrombocytopenia. Thus, accurate assessment of spleen size may be helpful in the clinical evaluation. Spleen length is not a precise estimate of spleen size because of the variation in spleen configuration, and spleen volumes measured by edging techniques can be tedious. We present a new method of measuring the functional spleen volume by liver-spleen scan (LSSs), validation experiments and some clinical data. METHODS: The method involves measurement of the total spleen counts by SPECT and dividing by a representative voxel concentration on a single frame to obtain the organ volume. Validation included phantom studies and clinical evaluation in 443 consecutive patients, including 216 with histologic assessments of chronic liver disease (CLD) and 11 healthy volunteers. RESULTS: A calibration factor determined from phantoms was used to convert the calculated volume (CV) to the "true" volume (V): V = CV (0.956) - 66.5 (r = 0.9991; P < 0.001). The volume calculations were validated in a second group of phantoms (r= 0.981; P < 0.0001). Spleen volumes were expressed as volume (cm3) and as volume per pound ideal body weight (IBW) (cm3/lb) (the conversion factor to convert cm3/lb IBW to cm3/kg IBW is 2.2). Clinical studies of reproducibility included demonstration of a significant (P < 0.0001) linear correlation between volumes calculated from repeat LSSs within 9 mo of the initial LSS in 11 healthy volunteers and 32 patients with CLD: y = 1.02x - 25; r = 0.968. The correlation with spleen volumes from autopsy or splenectomy was significant: y = 0.766x + 57; r = 0.845; P < 0.001. The normal spleen volume in 11 patients was 201 +/- 77 cm3 and 1.43 +/- 0.68 cm3/lb IBW (upper limits of normal: 335 cm3 or 2.5 cm3/lb IBW). In 443 consecutive LSSs over 15 mo, half of the patients had spleen volumes above the upper limits of healthy volunteers, and CLD was present in 90.9% of these patients. In 216 patients with histologically proven liver disease, a progressive increase in the percentage of spleen volumes above the upper limits of normal was noted from no fibrosis (10%) to mild to moderate fibrosis (36.7%) to early cirrhosis (52%) to advanced liver disease (75%). The correlation of spleen volume with platelet count was excellent (r = 0.7635; P < 0.005). CONCLUSION: This novel spleen volume measurement detects serious liver disease and correlates with splenic hyperfunction.

Interferon alfa-2b alone or in combination with ribavirin for the treatment of relapse of chronic hepatitis C. International Hepatitis Interventional Therapy Group.

BACKGROUND: Interferon alfa is the only effective treatment for patients with chronic hepatitis C. Forty percent of patients have an initial response to this therapy, but most subsequently relapse. We compared the effect of interferon alone with that of interferon plus oral ribavirin for relapses of chronic hepatitis C. METHODS: We studied 345 patients with chronic hepatitis C who relapsed after interferon treatment. A total of 173 patients were randomly assigned to receive standard-dose recombinant interferon alfa-2b concurrently with ribavirin (1000 to 1200 mg orally per day, depending on body weight) for six months, and 172 patients were assigned to receive interferon and placebo. RESULTS: At the completion of treatment, serum levels of hepatitis C virus (HCV) RNA were undetectable in 141 of the 173 patients who were treated with interferon and ribavirin and in 80 of the 172 patients who were treated with interferon alone (82 percent vs. 47 percent, P<0.001). Serum HCV RNA levels remained undetectable 24 weeks after the end of treatment in 84 patients (49 percent) in the combination-therapy group, but in only 8 patients (5 percent) in the interferon group (P<0.001). Sustained normalization of serum alanine aminotransferase concentrations and histologic improvement were highly correlated with virologic response. Base-line serum HCV RNA levels of 2 x 10(6) copies per milliliter or less were associated with higher rates of response in both treatment groups. Viral genotypes other than type 1 were associated with sustained responses only in the combination-therapy group. Combined therapy caused a predictable fall in hemoglobin concentrations but otherwise had a safety profile similar to that of interferon alone. CONCLUSIONS: In patients with chronic hepatitis C who relapse after treatment with interferon, therapy with interferon and oral ribavirin results in higher rates of sustained virologic, biochemical, and histologic response than treatment with interferon alone.

Functional measurement of nonfibrotic hepatic mass in cirrhotic patients.

OBJECTIVES: We have postulated that the perfused hepatic mass (PHM) can be estimated by quantitative (volumetric) liver spleen scan (QLSS) using single photon emission computed tomography assessment of sulfur colloid distribution between liver, spleen, and bone marrow. Thus, this parameter should correlate with the amount of functioning tissue in the liver. As a "gold standard" estimate of the nonfibrotic functioning hepatic mass, the weight of the liver at autopsy or transplant was corrected for the amount of scar tissue present. QLSS parameters were correlated with functional hepatic mass in 13 patients with advanced liver disease with liver available at transplant (8 patients) or autopsy (5 patients) who had prior QLSS. METHODS: Greater than 1000 mm2 of a liver tissue was assessed histologically in all patients and from more than 2 regions of the liver in 9 of 13 patients. The total fibrosis score (TFS) (range, 0-17.5) was calculated as a semiquantitative estimate of hepatic fibrosis. The ratio of functioning tissue was calculated as (1 - TFS/20) and the amount of functioning tissue as the nonfibrotic weight (NFW): NFW = liver weight x (1--TFS/20). QLSS parameters were measured postprandially and 30 min after injection of 5 mCi of technetium Tc 99m sulfur colloid. Pixel and total counts from the liver, spleen, and bone marrow as well as organ length were measured. Liver/bone marrow index and liver/spleen index were calculated. The perfused hepatic mass (PHM) was defined as the mean of the liver/bone marrow index and liver/spleen index. RESULTS: All patients had cirrhosis: alcoholic (1 patient), alcoholic with alcoholic hepatitis (1 patient), hepatitis B (3 patients), hepatitis C (6 patients), hepatitis C with hepatocellular carcinoma (1 patient), and primary sclerosing cholangitis (n = 1). The ratio of functioning tissue was 0.54 +/- 0.07; liver weight 1215 +/- 317 g; and NFW = 658 +/- 193 g. The PHM = 55 +/- 14. The PHM calculated from the QLSS correlated strongly with the NFW (functioning tissue) at autopsy/transplant: NFW = 13 PHM - 55; r = 0.9505; p < 0.0001). CONCLUSIONS: In cirrhotic patients (a) we have confirmed that the sulfur colloid distribution by QLSS is determined by the perfused hepatic mass, and (b) the amount of functioning tissue can be precisely estimated by QLSS parameters.

Treatment of chronic hepatitis C with consensus interferon: a multicenter, randomized, controlled trial. Consensus Interferon Study Group.

This multicenter, randomized, controlled, double-blind, phase III study in 704 patients with chronic hepatitis C infection compared treatment with consensus interferon (CIFN), a non-natural recombinant type-1 interferon, with a standard regimen of recombinant interferon alfa-2b (IFN-alpha2b). Patients were randomized to receive CIFN at doses of 3 microg or 9 microg, or 15 microg IFN-alpha2b (3 million units), subcutaneously three times weekly for 24 weeks, followed by 24 weeks of observation. Efficacy was assessed by normalization of serum alanine transaminase (ALT) concentration and decrease in serum hepatitis C virus (HCV) RNA concentration below the limit of detection by reverse-transcription polymerase chain reaction (RT-PCR) (100 copies/mL). The beneficial effect of CIFN was greater with the 9-microg dose than the 3-microg dose. The sustained ALT and HCV RNA response rates were 20.3% and 12.1%, respectively, in the 9-microg CIFN cohort and 19.6% and 11.3%, respectively, in the 15-microg IFN-alpha2b cohort. However, patients receiving 9 microg of CIFN had a greater reduction in serum HCV RNA concentrations compared with patients receiving 15 microg IFN-alpha2b over the course of treatment (P < .01). Similarly, analysis of patients infected with HCV genotype 1 showed a greater reduction in serum HCV RNA concentration over the course of treatment for the 9-microg CIFN group when compared with the 15-microg IFN-alpha2b group (P < .01). In addition, a greater percentage of patients infected with HCV genotype 1 treated with 9 microg CIFN had undetectable HCV RNA concentrations when compared with patients in the 15-microg IFN-alpha2b cohort at the end of treatment (24% vs. 15%; P = .04). Improvements in liver histology were noted in all three treatment groups; 52% to 55% of the patients in the three cohorts had at least a 2-unit improvement in the Knodell score at the end of the posttreatment period. The adverse-events profiles were characteristic of treatment with type-1 interferon, and the incidences of anti-interferon antibody formation did not significantly differ among the three treatment groups. These results show that administration of 9 microg CIFN three times weekly for 6 months is safe and is effective in reducing serum HCV RNA concentration.

The liver-spleen scan as a quantitative liver function test: correlation with liver severity at peritoneoscopy.

Sulfur colloid distribution on liver-spleen scan is determined by the perfused Kupffer cell mass. The perfused Kupffer cell mass is proportional to the perfused hepatocyte mass, but is less affected by acute changes in hepatocyte function. Thus, sulfur colloid distribution parameters (precisely measured by quantitative liver-spleen scan [QLSS]) may be an excellent test of the perfused hepatic mass. Although no gold standard exists for confirmation, a close correlation should exist between liver disease severity assessed at peritoneoscopy and sulfur colloid distribution. Peritoneoscopy severity (scored as total peritoneoscopy score [PS]; range, 0-5) was assessed in 76 patients who also had QLSS. Multivariate equation were generated to estimate liver disease severity from the QLSS. These were then applied prospectively in 20 consecutive patients to validate these equations. In 76 patients, 62 were evaluated because of chronic liver disease (CLD) and included those with micronodular (20) and macronodular (20) cirrhosis with various degrees of severity (Child's A, 16; B, 29; C, 17). Multivariate analysis yielded a number of combinations of QLSS parameters that correlated with peritoneoscopic severity. These equations were used to estimate liver disease severity. Estimates of liver disease severity (estimated PS [EPS]) correlated well with the PS in these 76 patients (r = .9064; r2 = .8216; P < .0001). Adding histological fibrosis to the QLSS parameters yields an equation for estimating PS that was even more effective (r = .9462; r2 = .8953; P < .001). However, validation of multivariate equations requires confirmation of their value in a second population.(ABSTRACT TRUNCATED AT 250 WORDS)

Perfused Kupffer cell mass. Correlation with histology and severity of chronic liver disease.

The perfused Kupffer cell mass determines sulfur colloid distribution by liver spleen scan (LSS) and is proportional to the perfused hepatocyte mass. This accounts for the correlation of sulfur colloid distribution with tests of hepatic function and raises the question of whether the LSS can be used as a quantitative test of hepatic function. The recent ability to precisely measure sulfur colloid distribution by single-photon-emission computerized tomography (SPECT) prompted us to evaluate the clinical value in 329 consecutive patients with adequate LSS and clinical information, of which 27 apparent normals and 220 patients with chronic liver disease (CLD) were included in this study. The liver-bone marrow index (LBI) indicated the distribution of counts between the liver and bone marrow. The liver-spleen index (LSI) indicated the distribution between liver and spleen adjusted for spleen size. The LBI and LSI correlated with each other (r = 0.753; P < 0.001). The arithmetic mean of LBI and LSI was defined as the severity score. Detailed clinical evaluation was available in these patients and included 109 who had liver biopsy. A severity score in 27 normals was 102 +/- 5 (mean +/- SD) with all values > 85. The severity score correlated with hepatic fibrosis (r = -0.694; P < 0.001) in 109 patients with benign liver disease who had recent biopsies and with the Child-Pugh classification (r = 0.78; P < 0.001) in 220 patients with CLD.(ABSTRACT TRUNCATED AT 250 WORDS)

Raising the dose of interferon does not improve the response in chronic hepatitis C.

We report results of dose escalation to 5 or 6 million units (MU) three times weekly (t.i.w.) of interferon-alpha in 17 consecutive patients with chronic active hepatitis C who were not responding to 3 MU t.i.w. after > or = 12 weeks of therapy. The mean pretreatment alanine aminotransferase (ALT) level was 206 +/- 62 U/L and, at the time of dose escalation, 113 +/- 71 U/L. Two patients could not tolerate the dose escalation. The remaining 15 patients were treated for an additional 10 +/- 3.5 weeks. Three patients had a complete response 3-8 weeks after dose escalation. At the end of high-dose therapy, the mean ALT level was 105 +/- 76 U/L (n = 15). During the 6-month posttreatment follow-up time, the mean ALT level was 147 +/- 85 U/L. All three responders had a relapse. Increasing the dose of interferon-alpha to 5-6 MU t.i.w. in chronic hepatitis C patients who are not responding to interferon-alpha, 3 MU t.i.w., at the 12th week of therapy is unlikely to result in sustained normalization of ALT levels.

Effect of chronic portal hypertension on glutamine transport across rat intestinal brush border and basolateral membranes.

The present study examined the effect of chronic portal hypertension on the intestinal transport of glutamine across the brush border membrane (BBM) and the basolateral membrane (BLM) of the rat enterocyte. Chronic portal hypertension was induced by partial portal vein ligation, and the results were compared with results in sham-operated rats. Transport studies were performed by using established techniques of isolated membrane vesicles. In chronic portal hypertensive rats, transport of glutamine in BBM vesicles (BBMVs) exhibited significant inhibition in the maximal velocity (Vmax) of both the Na(+)-dependent and the Na(+)-independent transport processes, with no significant changes in the apparent Michaelis-Menten constant (Km) of the carrier systems. Similarly, chronic portal hypertension caused a significant decrease in the Vmax of the Na(+)-dependent and the Na(+)-independent uptake processes in intestinal BLM vesicles (BLMVs), with no change in the apparent Km of the uptake systems. These changes in glutamine transport in BBMVs and BLMVs brought about by chronic portal hypertension are not due to differences in the relative purity of the vesicular preparations between the portal hypertensive and sham-operated rats, because similar degrees of enrichment and depurification of marker enzyme activities were seen in final vesicular preparations in the two rat groups. These results demonstrate that in chronic portal hypertension, glutamine transport across both poles of the enterocyte is impaired. At both the BBM and BLM domains, the impairment appears to be mediated via a decrease in the number (and/or activity) of the glutamine carrier systems, with no changes in their affinity.(ABSTRACT TRUNCATED AT 250 WORDS)

5-Methyltetrahydrofolate transport in basolateral membrane vesicles from human liver.

Transport of 5-methyltetrahydrofolate was studied in vesicles isolated from the basolateral membrane (BLM) of human liver. Uptake was mostly via transport into an osmotically active intravesicular space, with some membrane binding (approximately 20%). Transport was more rapid with an imposed pH gradient (pHout = 5.0, pHin = 7.5) as compared with either pHout = pHin = 5.0 or pHout = pHin = 7.5. Transport under the influence of a pH gradient showed a transient overshoot; uptake at 60 s was 4.2 times higher than at equilibrium (60 min). Transport in the presence of a pH gradient was saturable; apparent Km = 0.55 mumol/L and Vmax = 1.98 nmol.g protein-1.10 s-1. Transport was not saturable at pHout = pHin = 7.5. Transport was inhibited by the structural analogs 5-formyltetrahydrofolate, folic acid, and methotrexate, and was electroneutral in nature. These results suggest that 5-methyltetrahydrofolate transport in human BLM vesicles is via carrier-mediated cotransport with hydrogen ions.

Globulin correction of the albumin gradient: correlation with measured serum to ascites colloid osmotic pressure gradients.

The albumin difference or gradient between serum ascites is presumed to be an effective estimate of the colloid osmotic pressure gradient, although this has never been directly demonstrated. The colloid osmotic pressure gradient is controlled by the degree of portal hypertension. Thus the albumin gradient is clinically useful in detecting patients with ascites caused by portal hypertension, although some overlap in such patients' albumin gradients exists compared with those of patients without portal hypertension. Part of this overlap is related to the inverse correlation of the albumin gradient with serum globulin; globulins also contribute to colloid osmotic pressure. The ability to calculate colloid osmotic pressure in serum and ascites with albumin and globulin concentration or to correct the albumin gradient for the impact of globulins might improve the clinical usefulness of the ascitic fluid analysis in determining the presence of portal hypertension in ascitic patients with borderline albumin gradients. Thus we developed equations to calculate colloid osmotic pressure from multivariate discriminate analyses of albumin and globulin concentrations in serial dilution samples of pooled serum and subsequently validated these equations, along with older methods of calculating colloid osmotic pressure. In an initial set of dilution experiments, globulin concentration was closely correlated with the colloid osmotic pressure to albumin concentration ratio (r = 0.956; p less than 0.001). Multivariate discriminate analysis yielded an equation for calculating colloid osmotic pressure from albumin (A) and globulin (G) concentration with a ratio of colloid osmotic pressure to albumin (calculated colloid osmotic pressure = A(1.058G + 0.163A + 3.11) and two other equations.(ABSTRACT TRUNCATED AT 250 WORDS)

Biotin transport in human liver basolateral membrane vesicles: a carrier-mediated, Na+ gradient-dependent process.

The characteristics of biotin transport into human liver were examined using purified liver basolateral membrane vesicle (BLMV) preparations. Biotin uptake by BLMVs was mostly due to transport of the vitamin into the inside of vesicles. In the presence of an Na+ gradient (out greater than in), biotin transport with time was significantly higher than that in the presence of a K+ gradient and showed transient accumulation (overshoot). High concentrations of unlabeled biotin and related compounds caused significant cis inhibition in biotin transport in the presence of an Na+ (but not a K+) gradient. Transport of biotin as a function of concentration in the presence of an Na+ gradient included a saturable component, while it was lower and linear in the presence of a K+ gradient. Apparent Km and Vmax of the saturable Na+ gradient-dependent component were 1.22 mumol/L and 4.76 pmol.mg protein-1 x 10 s-1, respectively. Induction of a negative or positive intravascular potential using valinomycin-K diffusion methodology did not affect biotin transport into BLMVs. Also, neither the anion-exchange inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid nor 4-acetamido-4-isothiocyanostilbene-2,2'-disulfonic acid caused significant inhibition in biotin transport. These results indicate that biotin transport into human liver occurs via a specialized, carrier-mediated transport system. This system is Na(+)-gradient dependent and transports the vitamin via an electroneutral process.

Fatty infiltration of the liver: quantification with phase-contrast MR imaging at 1.5 T vs biopsy.

Quantification of hepatic fat content by application of MR phase-contrast imaging (Dixon method) at 1.5 T was compared with results of biopsy in 16 patients with a variety of liver abnormalities. Motion artifact was suppressed by employing six or eight averages of short TR in-phase (echo offset, 0 msec), out-of-phase (echo offset, 1.1 msec), and in-phase (echo offset, 2.2 msec) spin-echo pulse sequences. The 360 degree out-of-phase sequence was used to assess the impact of T2* decay on this method of estimating fat fraction. A standard two-echo long TR sequence also was obtained in all patients. Histologic preparations from the biopsy specimens were examined by a pathologist who had no knowledge of the MR results and were graded according to overall visual assessment as belonging to one of four categories of fat fraction. Results of the MR-calculated apparent fat fraction were compared directly with biopsy category and were also placed in MR fat fraction categories, allowing estimation of the statistical correlation between the biopsy and MR grading systems. Eight of eight patients with biopsy categories indicating a fat fraction of less than 0.25 were computed by MR to have a fat fraction of less than 0.1. Seven of eight patients with biopsy categories indicating a fat fraction of greater than 0.25 were computed by MR to have a fat fraction of at least 0.24. The MR-calculated apparent fat fraction category correlated significantly with the histologic biopsy category (r = .86, p less than .01). When compared with the in-phase image, decreased signal from liver was visually apparent on the 180 degree out-of-phase images in all cases in which the fat fraction was at least 0.24, but there was no indication of fatty liver on the standard T1- or T2-weighted images. Calculated T2 also showed no correlation with degree of fatty deposition. Correction for T2* decay by using the 360 degree out-of-phase acquisition in addition to the standard 0 degree and 180 degree out-of-phase images had little effect on fat fraction computation. Phase-contrast MR is a promising noninvasive method for quantitative assessment of fatty deposition in the liver.