Quantitative Proteomics and Mechanistic Modeling of Transporter-Mediated Disposition in Nonalcoholic Fatty Liver Disease.

Understanding transporter-mediated drug disposition and pharmacokinetics (PK) in patients with nonalcoholic fatty liver disease (NAFLD) is critical in developing treatment options. Here, we quantified the expression levels of major drug transporters in healthy, steatosis, and nonalcoholic steatohepatitis (NASH) liver samples, via liquid-chromatography tandem mass spectrometry-based proteomics, and used the data to predict the PK of substrate drugs in the disease state. Expression of organic anion transporting polypeptides (OATPs) and multidrug resistance-associated protein (MRP)2 is significantly lower in NASH livers; whereas MRP3 is induced while no change was observed for organic cation transporter (OCT)1. Physiologically-based pharmacokinetic models verified with PK data from healthy subjects well recovered the PK in NASH subjects for morphine (involving OCT1) and its glucuronide metabolites (MRP2/MRP3/OATP1B), 99m TC-mebrofenen (OATP1B/MRP2/MRP3), and rosuvastatin (OATP1B/breast cancer resistance protein). Overall, considerations to altered protein expression can enable quantitative prediction of PK changes in subjects with NAFLD.

Hepatic extraction fraction: interest of its quantification in patients with hepatic tumours.

BACKGROUND/AIMS: This prospective study aimed to estimate the usefulness of the hepatic extraction fraction (HEF) in the context of the pre- and postoperative evaluation of patients with hepatic tumours. METHODOLOGY: Seventy patients with colorectal metastases (n=25), hepatocellular carcinoma (n=25), cholangiocellular carcinoma (n=6), gastric cancer metastases (n=5), hemangioma (n=5) and others (n=4) were included. Thirty patients underwent hepatectomy. Child-Pugh score, prothrombin, albumin, ALT, AST, AF, LDH, total, direct and indirect bilirubin, platelet number as well as the HEF were evaluated in the preoperative period and one month after hepatectomy. RESULTS: Preoperative evaluation of HEF values between Child-Pugh A (93.6±17.3%) and Child-Pugh B/C (n=13; 58.1±28.6%) demonstrated significant differences (p=0.001). We found a high negative correlation between the preoperative HEF and ALT (p<0.001), AST (p<0.001), AF (p<0.001), TB (p<0.001), IB (p<0.001) and DB (p<0.001), and also a high positive correlation between the preoperative HEF and albumin (p<0.001) or prothrombin (p<0.01). All operated patients had a normal HEF and a positive correlation between the postoperative HEF and albumin (p<0.05) at one month after surgery. CONCLUSIONS: The HEF allows a dynamic evaluation of hepatocellular function, which is not possible with other clinical, biological and radiological methods.

Validation of 99mTechnetium-labeled mebrofenin hepatic extraction method to quantify meal-induced splanchnic blood flow responses using a porcine model.

The aim of this study was to evaluate the measurement of the total splanchnic blood flow (SBF) using a clinical diagnostic method based on Fick's principle and hepatic extraction of 99mTc-mebrofenin (99mTc-MBF) compared with a paraaminohippuric acid (pAH) dilution method in a porcine model. Another aim was to investigate whether enterohepatic cycling of 99mTc-MBF affected the SBF measurement. Five indwelling catheters were placed in each pig (n = 15) in the portal, mesenteric, and hepatic veins, as well as in the aorta and the vena cava. The SBF was measured using both methods. The portal blood flow; the intestinal and hepatic oxygen uptake; the net fluxes of oxygen, lactate, and glucose; and the extraction fraction (EF) of 99mTc-MBF were measured before and for 70 min after feeding. The mean baseline SBF was 2,961 ml/min vs. 2,762 ml/min measured by pAH and 99mTc-MBF, respectively, and increased significantly to 3,977 ml/min and 3,981 ml/min postprandially. The hepatic EF of 99mTc-MBF decreased from 40% at the start of the investigation to 16% 70 min after feeding. The arterial-portal difference in 99mTc-MBF concentration was 0.21% (P = 0.48), indicating no intestinal extraction or metabolism. The clinical method for measuring the SBF based on hepatic 99mTc-MBF extraction is robust compared with the indicator dilution method, despite the decrease seen in hepatic extraction of 99mTc-MBF. Because there was no difference in the content of 99mTc-MBF between the arterial and portal vein plasma, the SBF can be calculated from an arterial and a hepatic vein sample.

Preparation of 99mTc(CO)3-Carboxymethylthioethyl iminodiacetic acid and evaluation as a potential renal imaging agent.

UNLABELLED: The ligand, carboxymethylthioethyl iminodiacetic acid (CMT-IDA) has a suitable array of donor atoms for coordination with [99mTc(CO)3]+ core, wherein the resultant complex is expected to possess free carboxylic residues contributing towards hydrophilicity of the complex. The aim of the studies was to study the renal clearance of 99mTc(CO)3- labeled CMT-IDA and determine the potential of the complex towards its use as a renal tubular imaging agent. METHODS: CMT-IDA was radiolabeled with the [99mTc(CO)3(H2O)3]+ precursor and was characterized by reverse phase HPLC gradient elution system. Stability, hydrophilicity and plasma protein binding studies were carried out for the complex. Biodistribution studies were carried out in normal male Swiss mice at 10 min.p.i. and 2 h.p.i. The clearance was estimated from the activity observed in the urinary bladder by tying the urethra prior to injection of the complexes under study. Imaging studies were performed with male Swiss mice administered with [99mTc(CO)3(CMT-IDA)]-2 at 30 min. p.i. and blocking studies were carried out by intraperitoneal injection of probenecid 10 min. prior to the injection of the radiotracer. RESULTS: [99mTc(CO)3(CMT-IDA)]-2 could be obtained in > 98% radiochemical purity. The complex showed renal clearance of 71.0� 5.9% ID at 10 min.p.i. which increased to 84.1� 10.6% ID at 2 h.p.i., with no major activity in blood, liver, heart, lungs, stomach and spleen. However, the intestinal uptake was high (10.3� 2.0% ID) at 2 h.p.i. Scintigraphic image of the animal injected with probenecid showed an increase in the activity in kidneys indicating excretion of the [99mTc(CO)3(CMT-IDA)]-2 complex via tubular pathway. CONCLUSION: The complex, [99mTc(CO)3(CMT-IDA)]-2 has shown excellent renal clearance and thereby can be explored further for potential use as an agent towards assessing effective renal plasma flow.

Partially polymerized liposomes: stable against leakage yet capable of instantaneous release for remote controlled drug delivery.

A critical issue for current liposomal carriers in clinical applications is their leakage of the encapsulated drugs that are cytotoxic to non-target tissues. We have developed partially polymerized liposomes composed of polydiacetylene lipids and saturated lipids. Cross-linking of the diacetylene lipids prevents the drug leakage even at 40 °C for days. These inactivated drug carriers are non-cytotoxic. Significantly, more than 70% of the encapsulated drug can be instantaneously released by a laser that matches the plasmon resonance of the tethered gold nanoparticles on the liposomes, and the therapeutic effect was observed in cancer cells. The remote activation feature of this novel drug delivery system allows for precise temporal and spatial control of drug release.

(99m)Tc sulfur colloid and (99m)Tc mebrofenin hepatobiliary functional liver imaging in normal and diabetic rats.

OBJECTIVES: To use (99m)Tc sulfur colloid ((99m)Tc-SC) and (99m)Tc mebrofenin ((99m)Tc-BrIDA) to study liver function in normal and diabetic rats. MATERIALS AND METHODS: Radionuclide imaging was performed on 2 groups of rats, using (99m)Tc-SC for one group and (99m)Tc-BrIDA for the other (20 rats per group) before and after induction of diabetes mellitus (DM) using streptozotocin administration (55 mg/kg i.p.). Dynamic acquisition was obtained for 1 h after the injection of 37 MBq of radiotracer. For the (99m)Tc-SC group, organ/tissue uptake was determined by drawing regions of interest (ROI) over the heart, liver, spleen and also the whole body (WB). The ratio of the ROI of each organ to the WB ROI was calculated. For (99m)Tc-BrIDA, ratios of cumulative count rates in liver, liver parenchyma, biliary tree and abdomen ROI to a WB ROI were also calculated. Statistical analysis was performed to compare the ratios of organ/tissue uptake to WB uptake before and after DM induction using the paired t test. RESULTS: (99m)Tc-SC uptake ratios (means ±SD) showed a lower liver-to-WB uptake ratio (0.75 ± 0.05) in the rats after DM induction compared to baseline (0.81 ± 0.06), while the cardiac blood pool showed higher uptake ratios in the rats after DM induction (p = 0.026). For (99m)Tc-BrIDA, there was no significant difference in radiotracer uptake ratios obtained from the rats before and after DM induction (p = 0.41). CONCLUSION: Using functional liver imaging, there was a statistically significant decrease in the liver phagocytic/reticuloendothelial system function after DM induction, as evidenced by decreased (99m)Tc-SC liver uptake and increased blood pool compared to prediabetes, while the hepatobiliary function remained unchanged after DM induction using (99m)Tc-BrIDA imaging.

Transporters involved in the hepatic uptake of (99m)Tc-mebrofenin and indocyanine green.

BACKGROUND & AIMS: (99m)Tc-mebrofenin hepatobiliary scintigraphy (HBS) and the indocyanine green (ICG) clearance test are used for the assessment of hepatic function before and after liver surgery. The hepatic uptake of (99m)Tc-mebrofenin and ICG is considered similar to the uptake of organic anions such as bilirubin and bile acids. Little is known about hepatic uptake mechanisms of both compounds and recent evidence suggests that the hepatic transporters for ICG and (99m)Tc-mebrofenin are distinct. The aim of this study was to identify the specific human hepatic transporters of (99m)Tc-mebrofenin and ICG. METHODS: The uptake of (99m)Tc-mebrofenin was investigated in cRNA-injected Xenopus laevis oocytes expressing human OATP1B1, OATP1B3, OATP2B1, or NTCP. Chinese hamster ovary (CHO) cells stably expressing OATP1B1, OATP1B3, OATP2B1, or NTCP were used as a mammalian expression system. ICG transport into CHO cells was additionally imaged with confocal microscopy. RESULTS: We demonstrated that OATP1B1 and OATP1B3 are involved in the transport of (99m)Tc-mebrofenin. OATP1B1 showed an approximately 1.5-fold higher affinity for (99m)Tc-mebrofenin compared to OATP1B3. ICG is transported by OATP1B3 and NTCP. CONCLUSIONS: The transporter specificity of (99m)Tc-mebrofenin and ICG partially overlaps as both compounds are transported by OATP1B3. (99m)Tc-mebrofenin is also taken up by OATP1B1, whereas ICG is additionally transported by NTCP.

Evaluation of (99m)technetium-mebrofenin and (99m)technetium-sestamibi as specific probes for hepatic transport protein function in rat and human hepatocytes.

PURPOSE: This study characterized 99mTc-Mebrofenin (MEB) and 99mTc-Sestamibi (MIBI) hepatic transport and preferential efflux routes (canalicular vs. basolateral) in rat and human sandwich-cultured hepatocytes (SCH). METHODS: 99mTc-MEB and 99mTc-MIBI disposition was determined in suspended hepatocytes and in SCH in the presence and absence of inhibitors and genetic knockdown of breast cancer resistance protein (Bcrp). RESULTS: The general organic anion transporting polypeptide (Oatp/OATP) inhibitor rifamycin SV reduced initial 99mTc-MEB uptake in rat and human suspended hepatocytes. Initial 99mTc-MIBI uptake in suspended rat hepatocytes was not Na+-dependent or influenced by inhibitors. Multidrug resistance-associated protein (Mrp2/MRP2) inhibitors decreased 99mTc-MEB canalicular efflux in rat and human SCH. 99mTc-MEB efflux in human SCH was predominantly canalicular (45.8 +/- 8.6%) and approximately 3-fold greater than in rat SCH. 99mTc-MIBI canalicular efflux was similar in human and rat SCH; basolateral efflux was 37% greater in human than rat SCH. 99mTc-MIBI cellular accumulation, biliary excretion index and in vitro biliary clearance in rat SCH were unaffected by Bcrp knockdown. CONCLUSION: 99mTc-MEB hepatic uptake is predominantly Oatp-mediated with biliary excretion by Mrp2. 99mTc-MIBI appears to passively diffuse into hepatocytes; biliary excretion is mediated by P-gp. The SCH model is useful to investigate factors that may alter the route and/or extent of hepatic basolateral and canalicular efflux of substrates.

Adenosine triphosphate-binding cassette subfamily C member 2 is the major transporter of the hepatobiliary imaging agent (99m)Tc-mebrofenin.

UNLABELLED: The organic anion (99m)Tc-N-[2-[(3-bromo-2,4,6-trimethylphenyl)-amino]-2-oxoethyl]-N-(carboxymethyl)-glycine ((99m)Tc-mebrofenin) and its analogs are widely used for hepatobiliary imaging. Identification of the mechanisms directing bile canalicular transport of these agents will provide insights into the basis of their hepatic handling for assessing perturbations. METHODS: We performed studies in animals, including healthy Fischer 344 rats or rats treated with carbon tetrachloride or intrasplenic cell transplantation and healthy Wistar rats or HsdAMC:TR-Abcc2 mutant rats in Wistar background. Onset of hepatic inflammation was verified by analysis of carbon uptake in Kupffer cells. Hepatic clearance of (99m)Tc-mebrofenin was studied with dynamic imaging, and fractional retention of peak hepatic mebrofenin activity after 60 min was determined. Changes in the expression of bile canalicular transporters were analyzed by real-time polymerase chain reaction and Western blots. RESULTS: Carbon tetrachloride and cell transplantation produced hepatic inflammation with activation of Kupffer cells, resulting in a rapid decline in the expression of the bile canalicular transporters Abcb4, Abcb11, and Abcc2. Among these transporters, decreased expression of Abcc2 was most prominent, and this decline persisted for 4 wk. Next, we examined (99m)Tc-mebrofenin excretion in HsdAMC:TR-Abcc2 mutant rats (in which Abcc2 expression is naturally inactivated), compared with their healthy counterparts. In healthy HsdRccHan:WIST rats, only 23% +/- 3% of the peak (99m)Tc-mebrofenin activity was retained after 60 min. By contrast, in HsdAMC:TR-Abcc2 mutant rats, 73% +/- 5% of the peak (99m)Tc-mebrofenin activity was retained (P < 0.001). Moreover, the administration of cyclosporin A markedly inhibited (99m)Tc-mebrofenin excretion in healthy rats, with no further effect on already impaired (99m)Tc-mebrofenin excretion in HsdAMC:TR-Abcc2 mutant rats. Hepatic excretion of (99m)Tc-mebrofenin was largely dependent on Abcc2. This molecular basis of (99m)Tc-mebrofenin excretion will advance studies of pathophysiologic mechanisms in hepatic Abcc2 pathways.

Assessment of accuracy and precision of (99m)Tc-HEPIDA clearances determined by means of a simplified method.

BACKGROUND: The aim of the present study was the assessment of the accuracy and precision of our own simplified method for the determination of (99m)Tc-HEPIDA liver clearance. MATERIAL AND METHODS: It has been assumed that archived results of plasma clearance (Cl(Pl)) and hepatic (Cl(Hp)), determined by means of multisample methods, could be legitimately used as a reference standard. The accuracy and precision of the simplified method was assessed by means of a Monte Carlo method alternatively utilizing three blood sampling times (T) of 68, 75 and 83 minutes post i.v. administration of (99m)Tc-HEPIDA. The corresponding alternative three urine voiding times (Y) were: 75, 80, and 95 min p.i. The analysed model was created accepting values of Cl(Pl) and Cl(Hp), of administered activity A(p) and parameters of biexponential function, describing the concentration C(t) decrease of the radiopharmaceutical (RF) in plasma during time as real values. Using the function C(t) for each individual, the plasma concentrations of RF at three sampling times, urinary clearance (Cl(Pl) - Cl(Hp)), and voided activity (A(Ur)(Y)) were calculated. Simulated random errors were added to the assumed blood sampling times T and to voiding time Y. To the activity A(p) and A(Ur)(Y), and RF plasma concentrations random errors were added, assuming normal distribution with relative SD from 0 to 5% and then clearance values were computed. For each process there were 5000 repeated simulated determinations. The accuracy of the simplified methods was assessed by comparing mean values of simulated clearance computations with the reference. Comparison of standard deviations with mean uncertainties enabled us to gain insight into the degree of agreement of the estimator of relative uncertainty with the coefficient of variation as a measure of precision. RESULTS: There were strong correlations between the reference clearance values and the mean values of determinations by means of the simplified procedure (r > 0.93). The correlations were practically insensitive to the uncertainty of pipetting. The lines of regression differed slightly from the lines of identity, giving an indication that there was a systematic error involved; it amounted to +4 ml/min at Cl(Pl) = 60 ml/min and to -7 ml/min for Cl(Pl) of 370 ml/min. For Cl(Pl) a bias of +6 ml/min was found for a clearance value of 16 ml/min and -13 ml/min at Cl(Pl) > 300 ml/min. At uncertainty of pipetting of 2%, a precision of 6-7% was found for Cl(Pl) of 300 ml/min. For Cl(Pl) of 200 and 150 ml/min the corresponding precisions were 7-8% and 10%, respectively. For Cl(Pl) of 200, 150 and 100 ml/min the corresponding precisions were 10, 12 and 17%, respectively. These precisions are 5 percent worse than those that were obtained from determinations by means of multisampling procedures.

Comparison of (99m)Tc-HEPIDA and (99m)Tc-MBrIDA from the standpoint of hepatic clearance determination-- preliminary communication.

BACKGROUND. In order to evaluate the functional capacity of the liver by means of clearance determination, the derivative of iminodiacetic acid ((99m)Tc-HEPIDA) has been used in recent decades. Because of recent problems with manufacturing and delivery of (99m)Tc-HEPIDA, an investigation was undertaken with the aim of testing whether a more widely available (99m)Tc-MBrIDA could be used for clearance determination and whether hepatic clearance measured with the use of this compound provides a similarly useful test of hepatic function. MATERIAL AND METHODS. Comparative investigations were performed in 73 patients of both sexes. The state of the efficiency of liver parenchyma was determined based on seven widely used biochemical tests, i.e. levels of: bilirubin, albumin, and gamma globulin; activity of AST, ALT, GGTP, and prothrombin index. The clearances of both radiopharmaceuticals, (99m)Tc-HEPIDA and (99m)Tc-MBrIDA, were determined by means of multisample technique. The results of determination were correlated among themselves and with the results of biochemical tests. The set of results of all estimations allowed a factorial analysis to be performed to find a common factor and to compute the values of factor loadings in particular tests. RESULTS. Obvious correlation between plasma and hepatic clearances of both radiopharmaceuticals was obtained and between plasma clearance of (99m)Tc-MBrIDA and hepatic clearance of (99m)Tc-HEPIDA. Correlation coefficients of (99m)Tc-MBrIDA clearance and the biochemical test results attained somewhat lower values than for (99m)Tc-HEPIDA clearance. Similarly, values of chi(2) test of independence of (99m)Tc-MBrIDA clearances and test results were also less close than for (99m)Tc-HEPIDA clearances. Factorial analysis showed that common factor loading is greatest for hepatic clearance of (99m)Tc-HEPIDA; the values of two loadings of (99m)Tc-MBrIDA clearances are very close, but somewhat lower than those for (99m)Tc-HEPIDA. CONCLUSIONS. From the performed investigations it is possible to conclude that (99m)Tc-MBrIDA clearances may be used for the evaluation of liver parenchyma performance, even if the results may not be as certain as those obtained using (99m)Tc-HEPIDA.

Use of tc-99m mebrofenin as a clinical probe to assess altered hepatobiliary transport: integration of in vitro, pharmacokinetic modeling, and simulation studies.

PURPOSE: Transport of the hepatobiliary scintigraphy agent Tc-99m mebrofenin (MEB) was characterized and simulation studies were conducted to examine the effects of altered hepatic transport on MEB pharmacokinetics in humans. METHODS: MEB transport was investigated in Xenopus laevis oocytes expressing OATP1B1 or OATP1B3, and in membrane vesicles prepared from HEK293 cells transfected with MRP2 or MRP3. A pharmacokinetic model was developed based on blood, urine and bile concentration-time profiles obtained in healthy humans, and the effect of changes in hepatic uptake and/or excretion associated with disease states (hyperbilirubinemia and cholestasis) on MEB disposition was simulated. RESULTS: MEB (80 pM) transport by OATP1B1 and OATP1B3 was inhibited by rifampicin (50 microM) to 10% and 4% of control, respectively. MEB (0.4 nM) transport by MRP2 was inhibited to 12% of control by MK571 (50 microM); MRP3-mediated transport was inhibited to 5% of control by estradiol-17-beta-glucuronide (100 microM). A two-compartment model described MEB (2.5 mCi) systemic disposition in humans (systemic clearance = 16.2 +/- 2.7 ml min(-1) kg(-1)); biliary excretion was the predominant route of hepatic elimination (efflux rate constants ratio canalicular/sinusoidal = 3.4 +/- 0.8). Based on simulations, altered hepatic transport markedly influenced MEB systemic and hepatic exposure. CONCLUSIONS: MEB may be a useful probe to assess how altered hepatic function at the transport level modulates hepatobiliary drug disposition.

Systemic and local release of inflammatory cytokines regulates hepatobiliary excretion of 99mTc-mebrofenin.

OBJECTIVES: Imaging agents capable of providing cell compartment-specific information will facilitate studies of pathophysiological mechanisms, natural history of diseases, and therapeutic development. To demonstrate the effects of liver injury on the disposal of the organic anion mebrofenin, we performed animal studies. METHODS: Acute liver injury was induced in Fischer 344 rats with 0.25-1 ml/kg single doses of carbon tetrachloride followed by studies of animals over 4 weeks. The liver injury was analyzed by blood tests and histological grading. Additional rats were treated with lipopolysaccharide, interleukin-6 or tumor necrosis factor-alpha to activate inflammatory events. Hepatic clearance of Tc-mebrofenin was studied with dynamic imaging and fractional retention after 60 min of peak hepatic mebrofenin activity was determined. RESULTS: In healthy rats, only 24+/-2% of peak mebrofenin activity was retained in the liver after 60 min. By contrast, 24 h after carbon tetrachloride, virtually all mebrofenin activity was retained in the liver (P<0.001). Three weeks were required for mebrofenin excretion to become normal after carbon tetrachloride administration. In this situation, we found that Kupffer cell activity was increased. In addition, the abnormality in mebrofenin excretion was reproduced by lipopolysaccharide, which activates Kupffer cells. Moreover, mebrofenin excretion was highly sensitive to interleukin-6 and/or tumor necrosis factor-alpha, which help mediate the Kupffer cell response. CONCLUSION: Hepatobiliary excretion of mebrofenin was affected rapidly and over an extended period by inflammatory cytokines released after liver injury. The remarkable sensitivity of mebrofenin excretion to cytokines suggests that Tc-mebrofenin imaging will be helpful for assessing cytokine-mediated liver inflammation.

Parameters obtained by hepatobiliary scintigraphy have significant correlation with biochemical factors early after liver transplantation.

BACKGROUND: Early postoperative hepatobiliary scintigraphy after liver transplantation is performed worldwide, but data on its significance for graft function are currently limited. PURPOSE: To examine the correlation between the result of early postoperative hepatobiliary scintigraphy and pre- and postoperative biochemical parameters in liver transplantation (LTx) patients. MATERIAL AND METHODS: Six parameters of hepatobiliary scintigraphy using (99m)Tc mebrofenin were statistically analyzed in 108 LTx patients: 1) half-life of the activity of elimination of mebrofenin from the blood; 2) total clearance of mebrofenin from the blood due to all possible routes; 3) half-life of the activity due to liver uptake; 4) clearance of mebrofenin from the blood due to liver uptake; 5) time to maximal uptake in the liver; and 6) the hepatic extraction fraction (HEF) and biochemical data. Analysis between patients with preoperative normal liver function, familial amyloid polyneuropathy (FAP), and end-stage liver disease (non-FAP) was also performed. RESULTS: Univariate and multivariate analysis revealed that total bilirubin postoperative day 3 correlated with all three scintigraphic parameters, and peak aspartate aminotransferase and alanine aminotransferase correlated with HEF. The analysis between patients with FAP and non-FAP revealed no significant difference of scintigraphic data between the two groups. CONCLUSION: A significant correlation between early postoperative scintigraphic results and biochemical parameters was demonstrated.

Hepatobiliary scintigraphy after Kasai procedure for biliary atresia: clinical correlation and prognostic value.

BACKGROUND/PURPOSE: Kasai portoenterostomy (KP) is regarded as first-line treatment for biliary atresia, although its postoperative course is often unpredictable. Hepatobiliary scintigraphy using technetium-labeled iminodiacetic acid derivatives offers a dynamic, objective assessment both of parenchymal liver function and restored biliary excretion. The value of postoperative radionuclide scans was assessed prospectively in a large population of post-KP infants. METHODS: Radionuclide scans consisted of an intravenous dose of 20 MBq of 99mTc mebrofenin iminodiacetic acid and subsequent gamma camera imaging. Four scan variables were evaluated: the hepatic extraction fraction (HEF; ie, initial liver uptake divided by the peak vascular uptake), the half-life of tracer excretion (TEX), the shape of the excretion curve, and the presence of activity in the Roux loop at 4 hours postinjection. All infants had type 3 biliary atresia with a median age at KP of 59 days (24-120 days). To assess predictive value, outcome (clearance of jaundice and need for transplant) was assessed at 6 months (for 1-week scan) and 2 years (for 6-month scan). RESULTS: Eighty-seven infants underwent a radionuclide scan at 1 week post-KP. The median HEF was 34% (10%-90%). No relationship could be identified between HEF (P = .2) or excretion curve shape (P = .9) and outcome (at 6 months), and there were too few examples of a measurable TEX to allow meaningful comparison. The only predictive element at this time point was Roux loop activity (positive predictive value, 79%; negative predictive value, 53%; for "good" isotope bowel activity). Forty-four infants completed a second scan at 6 months. Median HEF increased from a baseline of 37% (11%-90%) to 64% (8%-100%) (P < .0001), although there was no significant intercorrelation (P = .12). The most predictive variables (of outcome at 2 years) were curve shape (positive predictive value, = 95%, negative predictive value, 82%) and TEX, and the least predictive was now Roux loop activity. CONCLUSIONS: Early (at 7 days) hepatic scintigraphy is not predictive of poor outcome in general, although Roux loop activity does indicate later success. Later hepatic scintigraphy (at 6 months) allows a detailed assessment of dynamic liver function with biliary excretion variables predictive of outcome in the medium term.

Evaluation of hepatobiliary scintigraphy as an indicator of hepatic function in domestic pigeons (Columba livia) before and after exposure to ethylene glycol.

This study investigated the use of quantitative hepatobiliary scintigraphy to assess liver function in 14 white Carneaux pigeons (Columba livia). Liver scintigraphy using 99mTc-mebrofenin was performed and liver function was quantified using deconvolutional analysis and the area under the normalized heart time-activity curve as previously described in the dog and horse. Liver biopsies were performed in all birds before and after toxin-induced liver damage with ethylene glycol. Before the induction of liver disease, all biopsy specimens showed varying degrees of granulomatous inflammation. After ethylene glycol administration, hepatic lesions were scored and compared with scintigraphic findings. Scintigraphic results showed a significant decrease (P = 0.04) in hepatic function using the area under the normalized time-activity curve. There was good correlation between the overall histologic score posttoxin exposure and scintigraphic measures of liver function (P < 0.03). Based upon these preliminary results, the area under the heart time-activity curve can determine hepatic extraction as a measure of hepatic parenchymal cell function. The results also showed that worsening hepatic cellular function correlated with increased histologic damage to the liver. The use of hepatobiliary scintigraphy using 99mTc-mebrofenin to determine liver function in pigeons has not been previously reported. Additional studies are warranted to evaluate the application of this technique in clinical patients and to establish the sensitivity of this technique.

Specific 99mTC-HEPIDA hepatic clearance--essential value ranges from a clinical stand-point.

BACKGROUND: Determinations of plasma 99mTc-HEPIDA clearance (ClPl) have been performed in some centres for 30 years to assess liver parenchyma damage, mostly for monitoring of organ performance in the course of various diseases. The main disadvantage of such a procedure rests with the fact that elimination of the compound from the system occurs not only via the liver and gall ducts, but also via the urinary route; the contribution of the latter compound being quite variable. This circumstance may lead to false assessment of liver parenchyma performance. A method has been developed therefore for assessment of specific hepatic clearance of 99mTc-HEPIDA (Cl(Hp)). Using this method it was demonstrated that results of Cl(Hp) correlated better with independently assessed degrees of liver impairment than did the values of ClPl. MATERIAL AND METHODS: To delineate ranges of Cl(Hp) that would provide valuable clinical information 134 individuals were studied, of whom 48 served as healthy controls and 86 had varying degrees of livers function impairment, resulting from various chronic diseases affecting the organs functional capacity. The latter was assessed on the basis of a series of commonly used biochemical indicators. RESULTS AND CONCLUSIONS: For delineation of meaningful ranges of 99mTc-HEPIDA specific hepatic clearance ROC curve method was used. The following results were obtained: Cl(Hp) >or= 150 ml min(-1) 1.72 m(-2)--excludes with high probability presence of substantial liver parenchyma damage; Cl(Hp)

Hepatobiliary function assessed by 99mTc-mebrofenin cholescintigraphy in the evaluation of severity of steatosis in a rat model.

PURPOSE: This study evaluated the utility of non-invasive assessment of hepatobiliary function by 99mTc-mebrofenin cholescintigraphy in a rat model of diet-induced steatosis. METHODS: Male Wistar rats (250-300 g) were fed a standard methionine- and choline-deficient (MCD) diet for up to 5 weeks, thereby inducing hepatic fat accumulation, progressive inflammation and fibrogenesis corresponding with clinical steatosis. 99mTc-mebrofenin pinhole scintigraphy was used to evaluate the hepatocyte mebrofenin uptake rate, the time of maximum hepatic uptake (T(peak)) and the time required for peak activity to decrease by 50% (T(1/2peak)). Scintigraphic parameters were correlated with biochemical and serological parameters and with liver histopathology. RESULTS: MCD diet induced mild steatosis after 1 week and severe steatosis with prominent inflammation after 5 weeks. T(peak), T(1/2peak) prolonged and the uptake rate decreased significantly, while the severity of steatosis increased (p<0.05). There was a strong, significant correlation between the severity of steatosis (histopathology, hepatic triglyceride content) and the 99mTc-mebrofenin uptake rate (r2=0.83, p<0.0001 and r2=0.82, p<0.0001, respectively). In addition, the uptake rate correlated significantly with the increased inflammation (plasma and hepatic TNF-alpha, r2=0.72, p<0.0001 and r2=0.52, p=0.001, respectively). The correlation of the uptake rate with hepatocellular damage was weak (AST and ALT, r2=0.29 and 0.32, respectively), but correlation with synthetic function was strong (prothrombin time, r2=0.70, p<0.001). CONCLUSION: Hepatobiliary function assessed by 99mTc-mebrofenin scintigraphy correlates with the extent and progression of steatosis. These results suggest a potential role for mebrofenin scintigraphy as a non-invasive functional follow-up method for disease progression in steatotic patients.