New insights in bilirubin metabolism and their clinical implications

Bilirubin, a major end product of heme breakdown, is an important constituent of bile, responsible for its characteristic colour. Over recent decades, our understanding of bilirubin metabolism has expanded along with the processes of elimination of other endogenous and exogenous anionic substrates, mediated by the action of multiple transport systems at the sinusoidal and canalicular membrane of hepatocytes. Several inherited disorders characterised by impaired bilirubin conjugation (Crigler-Najjar syndrome type I and type II, Gilbert syndrome) or transport (Dubin-Johnson and Rotor syndrome) result in various degrees of hyperbilirubinemia of either the predominantly unconjugated or predominantly conjugated type. Moreover, disrupted regulation of hepatobiliary transport systems can explain jaundice in many acquired liver disorders. In this review, we discuss the recent data on liver bilirubin handling based on the discovery of the molecular basis of Rotor syndrome. The data show that a substantial fraction of bilirubin conjugates is primarily secreted by MRP3 at the sinusoidal membrane into the blood, from where they are subsequently reuptaken by sinusoidal membrane-bound organic anion transporting polypeptides OATP1B1 and OATP1B3. OATP1B proteins are also responsible for liver clearance of bilirubin conjugated in splanchnic organs, such as the intestine and kidney, and for a number of endogenous compounds, xenobiotics and drugs. Absence of one or both OATP1B proteins thus may have serious impact on toxicity of commonly used drugs cleared by this system such as statins, sartans, methotrexate or rifampicin. The liver-blood cycling of conjugated bilirubin is impaired in cholestatic and parenchymal liver diseases and this impairment most likely contributes to jaundice accompanying these disorders.

Congenital nonhemolytic hyperbilirubinemias

Congenital nonhemolytic hyperbilirubinemias (CNH) are quite rare pathology of liver. They occur most often in children, but are common in adults too. A common feature of congenital nonhemolytic hyperbilirubinemias is an abnormal serum bilirubin level without other abnormalities in routine liver functional tests. Liver histology on light microscopy is normal. Hereditary genetics defect of enzymes taking part in metabolism of bilirubin is the cause of CNH. They are divided into two groups: with unconjugated hyperbilirubinemia (Crigler-Najjar syndrome, Gilbert syndrome) and conjugated hyperbilirubinemia (Dubin-Johnson syndrome and Rotor syndrome). Because CNH in adults are benign disorders and the prognosis is excellent, patients do not require any specific therapy. Is important to take the differential diagnosis. Once the diagnosis of congenital nonhemolytic hyperbilirubinemia is confirmed, patients should be informed of the disease process and its benign nature to prevent needless work-up in the future. In present, CNH are treated as cosmetic defects and no therapy is applied.

Safety of paclitaxel in a patient with ovarian cancer and hyperbilirubinemia due to Rotor's syndrome

BACKGROUND

Rotor's syndrome is a rare congenital disorder characterized by functional hyperbilirubinemia. Treatment decision may be challenging in a cancer patient with Rotor's syndrome, since the majority of the antineoplastic agents are metabolized in the liver and excreted via the biliary system. We report the first case of paclitaxel administration in a patient with ovarian cancer and elevated bilirubin levels due to Rotor's syndrome.

CASE

A 50-year-old woman with Rotor's syndrome had an exploratory laparotomy and was diagnosed to have stage IIIC epithelial ovarian cancer. The baseline serum bilirubin value was 15.3 mg/dL. She was started on a 50% dose of 87.5 mg/m(2) paclitaxel by 3-h infusion plus carboplatin AUC-6. The paclitaxel dose was increased by 25% at consecutive cycles until the standard dose of 175 mg/m(2)/3 h was achieved. Six cycles were administered without any metabolic derangement. The patient was rendered disease free with this treatment.

CONCLUSION

Paclitaxel appears to be safe to administer to cancer patients with functional hyperbilirubinemia.

Effects of luminal nutrients and small bowel transplants on congenital indirect hyperbilirubinemia

The Gunn rat is an excellent model of Crigler-Najjar syndrome, type 1. In previous studies we demonstrated that heterotopic 15-20-cm jejunal transplants from Wistar rats lowered serum bilirubin levels by 40%, and the reduction was transient (6 weeks). In contrast, orthotopic transplants decreased bilirubin levels by 60% and the effect persisted throughout the 8-week study. This study was initiated to identify the luminal substance(s) which are responsible for the persistent bilirubin-lowering effect of jejunal transplants. Thirty-one Wistar to Gunn 15-20-cm jejunal transplants were randomized to receive daily Thiry-Vella graft irrigation with 5 ml of normal saline (n = 8); bile salts (cholate + deoxycholate, 40 mg/ml, n = 5; fats (Microlipid, 20 mg/ml, n = 5); proteins (Casec caseinate, 40 mg/ml, n = 5); and sugars (Moducal + Polycose, 40 mg/ml, n = 8). Bilirubin levels were measured spectrophotometrically at weekly intervals. At 4 and 8 weeks, enzyme-induced bilirubin conjugation activity was measured using added known amounts of added bilirubin. Irrigation of the transplants with saline, protein, and sugar resulted in moderate (40%) lowering of serum total and indirect bilirubin levels. Fat was significantly more effective, lowering mean total bilirubin levels from 9.6 +/- 0.4 to 1.6 +/- 0.2 mg/dl at 6 weeks. After this time, bilirubin levels increased slightly. Bile salts were slightly less effective, lowering bilirubin levels at 6 weeks by only 75%. However, this effect persisted and at 8 weeks levels averaged 2.4 +/- 0.2 mg/dl. Conjugating enzyme activity in the transplants increased from 1.4 +/- 0.3 to 2.5 +/- 0.5 mg bilirubin conjugated/mg tissue/hr. Luminal fats and bile salts appear to augment enzyme-induced bilirubin conjugation in heterotopic jejunal transplant recipients.

Different biliary excretion systems for glucuronide and sulfate of a model compound; study using Eisai hyperbilirubinemic rats

The disposition of conjugated metabolites (sulfate and glucuronide) was investigated in Eisai hyperbilirubinemic rats (EHBR) and normal Sprague-Dawley (SD) rats by in vivo and liver perfusion methods. EHBR are mutant rats that have conjugated hyperbilirubinemia as an autosomal recessive trait inheritance, and they show impaired excretion of organic anions into the bile. 6-Hydroxy-5,7-dimethyl-2-methylamino-4-(3-pyridylmethyl) benzothiazole (E3040), a novel dual inhibitor of 5-lipoxygenase and thromboxane A2 synthetase, was used as a model compound, because the major metabolites of E3040 are glucuronide and sulfate. After the i.v. injection of [14C]E3040 to EHBR and SD rats, the plasma AUC for glucuronide was greater in EHBR than in SD rats. The cumulative biliary excretion of the glucuronide was impaired to a great extent in EHBR, and the urinary excretion was enhanced. There was no significant difference in the cumulative biliary and urinary excretion of sulfate between EHBR and SD rats. The influx, efflux and sequestration rates of E3040, measured by a multiple indicator dilution method in the perfused rat liver, were similar in EHBR and SD rats. The biliary excretion of the glucuronide formed in the liver, measured by the liver perfusion method, was also severely impaired in EHBR, so the recovery of the glucuronide in the outflow specimens was markedly enhanced. The disposition of the sulfate did not change in either type of rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythrocyte membrane transport of glutathione conjugates and oxidized glutathione in the Dubin-Johnson syndrome and in rats with hereditary hyperbilirubinemia

The Dubin-Johnson syndrome is manifested by conjugated hyperbilirubinemia and pigment accumulation in hepatocellular lysosomes. The TR-rat model is a phenotypic model of the Dubin-Johnson syndrome and is characterized by defective ATP-dependent transport of a group of nonbile acid organic anions, including glutathione-S-conjugates and oxidized glutathione, across the bile canaliculus. Similar ATP-dependent transport mechanisms have been described in erythrocytes. Intact erythrocytes and inverted erythrocyte membrane vesicles from Dubin-Johnson patients, TR-rats and appropriate controls were studied with regard to ATP-dependent transport of dinitrophenyl glutathione and oxidized glutathione. No significant differences were observed, indicating that the erythrocyte and canalicular ATP-dependent transporters for these substrates are functionally and potentially genetically distinct.

[Hyperbilirubinemia]

A 22-year-old woman had icteric sclerae since childhood. Five years ago of Gilbert-Meulengracht's disease was diagnosed (hyperbilirubinemia, normal other liver laboratory parameters, no evidence of hemolysis). The patient was admitted for re-evaluation. Apart from jaundice of the sclerae no other clinical symptoms were found. Analysis of urine revealed bilirubin and an increased urobilinogen. Serum bilirubin was also elevated. The differentiation of the bilirubin gave evidence of an increase of the direct (conjugated) bilirubin portion. Additional investigations (total coproporphyrin in the urine, isomer I and isomer III coproporphyrin excretion and bromsulphalein test) suggested Rotor's syndrome. Further examinations (oral cholecystography, liver biopsy) were not added because of relative invasiveness, lack of clinical consequences and opposition of the patient. Nevertheless the diagnosis of a Rotor's syndrome is highly probable.

A new rat mutant with chronic conjugated hyperbilirubinemia and renal glomerular lesions

A new mutant strain of inbred Sprague Dawley rats with autosomal recessive hyperbilirubinuria, were studied by biochemical, histologic, and ultrastructural methods. The plasma bilirubin concentration in the homozygote was significantly higher than that of the heterozygote, and about 80% of the bilirubin was conjugated. Plasma BSP and ICG clearance were both severely delayed in the homozygote. Plasma BSP elimination kinetics suggested that the pathophysiologic defect was not hepatic uptake or storage but rather in secretion into bile. Histopathology of the liver demonstrated brown pigment in the hepatocytes that appeared to be lipofuscin. The electron microscopic features of the hepatic pigment resembled those of the Dubin-Johnson syndrome. Homozygote histopathology also revealed glomerular lesions with mesangial expansion and proliferation in the kidneys. Immunohistologic studies disclosed mesangial granular deposition of IgG, IgA, and to a lesser degree, IgM and C3. These renal changes resembled those of IgA nephropathy. The spontaneous hyperbilirubinuric rat (EHBR) may be a useful animal model for studying constitutive conjugated hyperbilirubinemia, bilirubin metabolism, cholestasis, and glomerulonephropathy subsequent to hepatic dysfunction.

Primary shunt hyperbilirubinaemia: a variant of the congenital dyserythropoietic anaemias

A 19 year old Mauritian male presented with episodic nausea, abdominal discomfort and jaundice. Unconjugated hyperbilirubinaemia and erythroid hyperplasia without dyserythropoiesis led to the diagnosis of primary shunt hyperbilirubinaemia. The similarity between congenital dyserythropoietic anaemia and this entity suggests that patients with these lesions can be considered within a single spectrum of disorders, characterized as congenital ineffective erythropoiesis.

Serum PAF acetylhydrolase increases during neonatal maturation

Acetylhydrolase is an acid-labile, 43 kd protein that catalyzes the degradation of platelet activating factor (PAF), a potent phospholipid inflammatory mediator, to its biologically inactive metabolite lysoPAF. PAF has a short half-life, thus acetylhydrolase plays an important role in its regulation. Since previous work suggests that PAF may be involved in certain neonatal diseases such as necrotizing enterocolitis, we studied the effect of age on acetylhydrolase activity. Serum acetylhydrolase activity was quantified using radio-labelled PAF and measuring reaction products. Serum samples were obtained prospectively from 70 subjects ranging in age from 4 hr to 48 yr. Acetylhydrolase activity was lower for newborns (less than 3 wk) than all other age ranges (8.2 +/- 1.4 nmole/ml/min vs 30.0 +/- 1.6 nmole/ml/min, p less than .01). Furthermore, enzyme activity increased linearly with respect to the natural logarithm of age from 0 days to 6 weeks (r = 0.65, p less than .001). By 6 weeks of life acetylhydrolase activity approached values of older children and adults. Newborn acetylhydrolase activity was similar between term and preterm infants (8.6 +/- 1.9 nmole/ml/min vs 7.2 +/- 2.4 nmole/ml/min, p = NS). We conclude that acetylhydrolase activity is low in human neonates and increases during the first 6 weeks of life. These results suggest that newborn infants may be at increased risk for pathophysiologic processes mediated by PAF.

A case of Gilbert's syndrome combined with macroamylasemia

A 30-year-old Japanese male, who had no remarkable family history, visited our hospital with a complaint of abdominal pain, and unconjugated hyperbilirubinemia and hyperamylasemia were observed. He showed negative hemolysis tests, positive nicotinic acid test, low hepatic bilirubin UDP-glucuronyltransferase activity, decreased bilirubin diglucuronide and increased bilirubin monoglucuronide in bile, and a decrease in serum bilirubin after phenobarbital administration. He also showed high serum amylase level, low urine amylase level, and low amylase-creatinine clearance ratio. Gel filtration of serum with Sephadex G-200 revealed the existence of macroamylase. Countercurrent immunoelectrophoresis proved binding of serum amylase to lambda type IgA. From these results, the case was diagnosed as Gilbert's syndrome combined with macroamylasemia.

Effect of nicotinic acid administration on serum levels of bilirubin and iron in patients with porphyria cutanea tarda

Nicotinic acid (NA) administration in Gilbert's syndrome (GS) patients promotes an increment of bilirubin and of total iron serum levels, dependent on a defective hepatic bilitranslocase function and on a haemolytic effect of NA. In porphyria cutanea tarda (PCT): (1) the effect of nicotinic acid on bilirubinaemia is superimposable to that in controls; (2) a well documented disturbance of iron metabolism occurs; (3) but relationship between bilirubin and iron under NA load has never been investigated. The administration of 5.9 mumol/kg body weight of NA to 12 PCT patients, 10 GS subjects and nine healthy volunteers of comparable age resulted in: (1) normal behaviour of bilirubin parameters in PCT but higher bilirubinaemic values in GS subjects; (2) normal values of serum iron in GS subjects, but higher baseline values and lower sideraemic effect of nicotinic acid in PCT patients; (3) a normal NA half-life in PCT and enhanced in GS subjects. These findings confirm a defective bilirubin uptake and excretion by the liver of GS subjects with a normal iron metabolism. On the contrary, in our PCT patients a normal clearance of bilirubin occurs, but a complex disturbance of iron metabolism is well evident in baseline conditions as well as after NA administration. The latter being probably the consequence of an enhanced excretion of iron extraproduced by the haemolytic effect of NA.

Effect of different doses of S-adenosyl-L-methionine (SAMe) on nicotinic acid-induced hyperbilirubinaemia in Gilbert's syndrome

S-adenosyl-L-methionine (SAMe) has been shown to increase hepatocyte membrane fluidity thereby relieving signs of oestrogen-induced cholestasis. S-adenosyl-L-methionine might therefore prove effective in improving the efficiency of the transport of organic anions such as nicotinic acid (NA) and bilirubin which is impaired in Gilbert's syndrome (GS). In this study the effects on the metabolization rate of NA and bilirubin of two dosages of SAMe were evaluated in respect to placebo in ten male inpatients (mean age 24 years, range 16-31) with GS. Each patient received both SAMe (800 and 200 mg/day, respectively) and placebo treatment i.v. over a period of 10 days. The NA test (5.9 mumol/kg b.w. i.v.) was carried out in the same volunteers after each treatment. Unconjugated bilirubin (UCB) levels were significantly lower (p less than 0.01) after 800 mg/day SAMe than after placebo while the lower dosage of SAMe did not affect UCB values. The bilirubin time curve concentration, expressed as area under the curve (AUC), was significantly reduced (p less than 0.01) after 800 mg SAMe in comparison with the values obtained after placebo and 200 mg SAMe. Also plasma NA half-life was significantly reduced (p less than 0.01) by the higher dose of SAMe in respect to placebo and not by the lower dose.

Transplantation of isolated hepatocytes into the pancreas

In previous research into hepatocyte transplantation (HTX) the spleen was the preferred acceptor organ for isolated donor hepatocytes. In this study the pancreas was tested as an acceptor organ for HTX. HTX into the pancreas or spleen was performed by injection of 10(7) isolated hepatocytes into the parenchyma of these organs. Intrapancreatic hepatocytes showed good viability 3 months after syngenic HTX as assessed by histological and immunocytochemical parameters. Definite proof of sustained metabolic activity of normal hepatocytes, 3 months after transplantation into the pancreas of congenitally jaundiced rats, was obtained by demonstration of bilirubin conjugates in bile of the recipients: 4.0% of total biliary bilirubin was conjugated. Intrasplenic HTX, however, was more effective and resulted in a conjugated fraction of 17.7% of total biliary bilirubin (p less than 0.001). Reduction of total plasma bilirubin was significant with both methods, but more pronounced in intra-splenic HTX. Bile drainage from the hepatocellular transplant via the pancreatic excretory system into the gut was not observed: conjugated bilirubins were not found in pancreatic juice of HTX-treated jaundiced rats. Intrapancreatic HTX did not adversely affect the host rat; evidence of pancreatitis or diabetes was not found. It is concluded that the pancreas is a suitable acceptor organ for HTX. However, intrapancreatic HTX appears to be less effective than intrasplenic HTX in the treatment of enzyme deficiency disease.

Hypersideremic and hyperbilirubinemic effect of nicotinic acid in patients with Gilbert's syndrome

Nicotinic acid test (NA) administration is followed by a rise in unconjugated bilirubin and serum total iron in healthy man. A similar concomitant effect has never been investigated in Gilbert's syndrome (GS) patients, who by definition have a hyperbilirubinemia higher than that of controls. The aim of this study was to verify whether, in addition to the hyperbilirubinemic action, NA could induce parallel hypersideremia in GS subjects. The data we obtained confirm in GS patients: 1. the well-known hyperbilirubinemia; 2. a delayed NA plasma concentration curve, and document that in GS the hypersideremic effect is comparable to that of controls. Previous investigators reported that NA produces an equimolar rise of bilirubin and iron levels in healthy man. In our study the extent of the sideremic response to NA occurring in GS patients is comparable to that seen in controls, and appears unrelated to the bilirubinemic values. If the NA effects are based on the documented hemolytic properties of NA, a disturbance in bilirubin handling by the liver of GS subjects appears to be plausible in the presence of almost normal behavior of NA-induced hypersideremia.

Distribution of serum bilirubin conjugates in pediatric hepatobiliary diseases

We used a highly specific method, alkaline methanolysis-high performance liquid chromatography, for determining the concentration and patterns of the unconjugated and esterified bilirubin fractions in the sera of pediatric patients with hepatobiliary disease. Bilirubin-protein conjugates were assayed using a new method that selectively removes bilirubin reversibly bound to protein, allowing measurement of the tightly bound bilirubin-protein conjugates by use of a diazo method. Fifty-two serum samples from children with varying bilirubin concentrations and diagnoses were studied. Whereas no conjugated pigment was detectable in the serum samples of healthy children or in individuals with Gilbert syndrome or Crigler-Najjar syndrome, bilirubin monoester and diester conjugates and bilirubin-protein conjugates were present in the sera of children with cholestatic liver disease, and accounted for 69% +/- 15% of the total bilirubin in these samples. Bilirubin fractional analysis was incapable of differentiating extrahepatic biliary obstruction from hepatocellular disease, because of overlap between the groups. The presence of bilirubin-protein conjugates in serum always coincided with detection of bilirubin monoester and diester conjugates. The distribution of bilirubin and its conjugates in sera provides a sensitive, although nonspecific, measure of hepatic disease.

Relationships between serum bilirubins and production and conjugation of bilirubin. Studies in Gilbert's syndrome, Crigler-Najjar disease, hemolytic disorders, and rat models

The pattern of serum bilirubins was determined in serum of humans and rats with unconjugated hyperbilirubinemia due to increased pigment load or defective hepatic conjugation. Bilirubin ester conjugates were present in all serum samples tested and were identified as bilirubin 1-O-acyl glucuronides. In Gilbert's syndrome, the concentration of total conjugates was comparable to the values in healthy control subjects. Because the concentration of unconjugated pigment was increased, the fraction of conjugated relative to total bilirubins was markedly decreased. Sera from patients with Crigler-Najjar disease differed from those with Gilbert's syndrome by the higher unconjugated bilirubin levels and the undetectability of diconjugated bilirubins. A striking finding was that in hemolytic disease, the concentration of both monoconjugates and diconjugates was enhanced in parallel with the increase of unconjugated pigment. Therefore, the fraction of conjugated relative to total bilirubins remained within the normal range. As in Gilbert's syndrome, heterozygote R/APfd-j/+ rats with impaired hepatic bilirubin conjugation exhibit an increased unconjugated bilirubin level in serum, whereas the concentration of total conjugates was comparable to the values in normal rats. In serum of normal rats loaded intraperitoneally with unconjugated bilirubin, both unconjugated and mono- and diconjugated bilirubins were increased in parallel so that the ratio of unconjugated to esterified pigment remained unaffected. Decreased hepatic conjugation or increased bilirubin load was associated with a lower percentage of diconjugates relative to total conjugates both in human and rat serum. The present results are consistent with a compartmental model in which there is bidirectional transfer across the sinusoidal membrane for unconjugated bilirubin as well as for the bilirubin glucuronides. Because typical patterns of serum bilirubins are found in Gilbert's syndrome and patients with hemolytic hyperbilirubinemia, determination of esterified bilirubins in serum is of value to study the pathophysiology and the differential diagnosis of unconjugated hyperbilirubinemia.

Serum free fatty acids and bilirubin concentration during fasting in patients with Gilbert's syndrome and normal controls

The increments in serum concentrations of unconjugated bilirubin and free fatty acids (FFA) were measured 24 and 48 h after reduction of the caloric intake (400 cal/day) in 17 patients with Gilbert's syndrome (GS) and in 12 healthy control subjects. In males, both normal and with GS, the rise in serum bilirubin was statistically higher (p less than 0.01) as compared to females. On the contrary, no sex difference was found in FFA concentrations. A linear correlation (p less than 0.01) between bilirubin and FFA serum levels was present in normal males and in patients with Gilbert's syndrome of both sexes. Because bilirubin and FFA partly share a common, bilitranslocase-mediated, hepatic uptake mechanism, data reported support the hypothesis that a bilitranslocase function may be one of the metabolic defects in Gilbert's syndrome.

Dose dependence of nicotinic acid-induced hyperbilirubinemia and its dissociation from hemolysis in Gilbert's syndrome

The serum increments in unconjugated bilirubin and total iron were determined after intravenous administration of 5.90 mumol/kg body weight of nicotinic acid (NA) in 26 patients with Gilbert's syndrome (GS), seven patients with hemolytic anemia, and 13 healthy volunteers. The hyperbilirubinemic response, expressed as the area under time concentration curve of unconjugated bilirubin (AUCBR, milligrams per deciliter per 240 minutes) was significantly higher (P less than 0.01) in patients with GS than in controls and patients with hemolytic anemia, in whom no difference was observed. In contrast, comparable values of the hypersideremic effect (AUCFe, milligrams per deciliter per 240 minutes) were noticed among the three groups. In seven consecutive patients with GS, seven with hemolytic anemia, and four healthy volunteers, AUCBR, AUCFe, and the NA plasma half-life of the first fast slope of the curve were determined at three different doses of the drug (1.18, 2.95, and 5.90 mumol NA per kilogram body weight). A significant, dose-dependent increase in AUCBR was present in patients with GS, whereas it remained constant both in controls and in patients with hemolytic anemia. The NA plasma half-life was also significantly prolonged in GS with each of the three doses, but remained unchanged in the other two groups. In patients with GS, a linear correlation (r = 0.891, P less than 0.001) was present between AUCBR and NA plasma half-life. In contrast, the AUCFe value remained constant at the different doses used in the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Inaccurate values for direct bilirubin with some commonly used direct bilirubin procedures

We compared five methods for the determination of total and direct bilirubins in serum samples from normal controls, subjects with Gilbert's syndrome, and serum pools containing about 50 and 150 mg of total bilirubin per liter. The Kodak Ektachem method and a diazotized sulfanilic acid method with 0.15 mmol/L sodium nitrite concentrations are the only methods that gave accurate direct bilirubin values, as judged by liquid-chromatographic results. The aca method that involved p-nitrobenzene diazonium tetrafluoroborate and another diazotized sulfanilic acid method with a higher concentration of sodium nitrite (0.8 mmol/L) yielded falsely high values for direct bilirubin, which could lead to clinical confusion. The more recently introduced diazotized sulfanilic acid method of the aca gave substantially better results than the p-nitrobenzene diazonium tetrafluoroborate method but was still inaccurate. Systematic investigation of these procedures revealed that the overestimation of direct bilirubin by the diazotized sulfanilic acid method was related to the amount of unconjugated bilirubin present and its ability to react as direct bilirubin in the presence of higher concentrations of sodium nitrite. Inherent properties of p-nitrobenzene diazonium tetrafluoroborate appeared to be responsible for inaccuracies in that method, which could not be corrected by varying reagent concentration or the reaction conditions.

Impaired plasma clearance of nicotinic acid and rifamycin-SV in Gilbert's syndrome: evidence of a functional heterogeneity

Patients with Gilbert's syndrome (GS) have impaired clearance by the liver of some organic anions. We looked for possible differences in hepatic clearance of nicotinic acid (NA) and rifamycin-SV (R-SV) among GS patients, and examined the effect produced by these anions on the plasma levels of unconjugated bilirubin (UCB). Two subgroups of GS patients, GS1 and GS2, were differentiated according to their ability to handle R-SV and NA. Compared with a control group, the alteration of the half-life both of NA and R-SV was less marked in GS1 than in GS2. UCB plasma concentration after NA and R-SV loading was more greatly increased in GS2 than in GS1 patients. In addition, a striking correlation was found in all subjects studied between UCB and the half-life of NA and R-SV. These related alterations of plasma UCB and plasma half-life or organic anions suggests a common defect of hepatic uptake. It is hypothesized that this defect is located at the level of a hepatic plasma membrane carrier.

Serum bile acids in Gilbert's syndrome after oral load of chenodeoxycholic acid

Oral bile acid loading tests using 1 g of unconjugated chenodeoxycholic acid (CDA) were performed in subjects with Gilbert's syndrome before and after reduced caloric intake. The study was carried out to ascertain whether the hepatic handling of CDA was restricted in the same manner as recently described for ursodeoxycholic acid. In subjects with Gilbert's syndrome, the bile acid concentrations after the oral loading tests did not differ significantly from those found in reference groups. No differences were found in the serum bile acid values before and after caloric restriction, indicating that the bile acid handling was not influenced by the increased bilirubin levels obtained after fasting. Our results indicate that the hepatic handling of CDA is normal in Gilbert's syndrome.

Sex differences of nicotinate-induced hyperbilirubinemia in Gilbert's syndrome. Implication of bilitranslocase function

Intravenous administration of nicotinic acid (NA) is followed by an increase in serum unconjugated bilirubin level. This effect is higher in Gilbert's syndrome (GS) and this test has been used in the diagnosis of the syndrome. After administration of 5.9 mumol NA/kg body weight, the maximal increment of serum unconjugated bilirubin and the area under the bilirubin concentration time curve (AUC) were significantly higher (P less than 0.01) in GS males than in GS females. The half-life of the first fast slope of plasma disappearance curve of the drug was also significantly prolonged in GS males as compared to GS females (15.91 +/- 1.12 vs 9.13 +/- 1.25 min, mean +/- SEM, P less than 0.005). The maximal bilirubin increment and AUC were linearly correlated (P less than 0.01) with NA plasma half-life. Purified preparations of bilitranslocase, a liver plasma-membrane protein involved in bilirubin and sulfobromophthalein (BSP) transport, specifically bound NA and the drug competitively inhibited BSP uptake in rat liver plasma membrane vesicles (Ki = 50 nM). These data suggest that, in addition to the hemolytic effect of the drug, NA-induced hyperbilirubinaemia could be also due to a competition between the two anions at the sinusoidal plasma membrane level. A possible implication of bilitranslocase in GS is considered.

Plasma clearance of nicotinic acid and rifamycin-SV, and their interaction in Gilbert's syndrome: application of a compartmental model

The bicompartmental kinetics of nicotinic acid (NA) and rifamycin-SV (R-SV)--2 organic anions that probably share a common hepatic uptake mechanism--were studied in 7 cases of Gilbert's syndrome (GS) and in 7 healthy controls matched for sex and age. In GS the NA and R-SV uptake constants (K21) were significantly decreased. In GS patients, simultaneous loads of NA and R-SV, the latter at increasing doses, produced: 1) a progressive lowering only of R-SV K21; and 2) an increase in R-SV hepatic plasma reflux (K12). Changes in biliary excretion ( Kee ) and hepatocellular pool (Ke) of both NA and R-SV probably depend on the rates of uptake and reflux constants of the two anions. The study of the parameters of compartmental kinetics of NA and R-SV confirms that the two organic anions, which have different metabolic routes and/or a different affinity for intracellular carriers, share common uptake mechanisms.

A nonhuman primate model of Gilbert's syndrome

A Bolivian population of squirrel monkeys, Saimiri sciureus, exhibits several features of Gilbert's syndrome in man, and is proposed as a nonhuman primate model of the condition. The Bolivian population was found to have higher fasting (40.6 +/- 2.7 microM; mean +/- S.E.) and postcibal (9.9 +/- 0.9 microM) plasma unconjugated bilirubin concentrations (p less than 0.001) than a closely related Brazilian population (fasting 5.5 +/- 0.7 microM); postcibal (2.4 +/- 0.7 microM). After intravenous administration of [3H]bilirubin as a tracer dose or at 3.4 mumoles per kg body weight, there was delayed plasma clearance in the Bolivian monkeys. Hepatic UDP-glucuronyl transferase activity for bilirubin (164 +/- 25 nmoles per 30 min per gm liver) and biliary bilirubin diglucuronide to monoglucuronide ratios (2.9 +/- 0.2) were lower in Bolivian monkeys than in Brazilians (421 +/- 36 nmoles per 30 min per gm liver--p less than 0.01 and 4.1 +/- 0.1--p less than 0.02, respectively). Hepatic cytosol glutathione-S-transferase B activity (ligandin) levels were similar for the two populations. After phenobarbital therapy, fasting (11.1 +/- 0.9 microM) and postcibal (5.3 +/- 1 microM) plasma bilirubin concentrations in Bolivian monkeys were significantly reduced (p less than 0.001). Sulfobromophthalein clearance was slightly slower in the Bolivian than in the Brazilian monkeys. SGOT, lactate dehydrogenase, gamma-glutamyl transpeptidase and alkaline phosphatase activities were not increased in Bolivians. Fasting serum conjugated bile salt concentrations in Bolivian monkeys were lower than that in Brazilian monkeys (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Serum bile acids in Gilbert's syndrome before and after reduced caloric intake

Fasting and postprandial serum bile acids were determined before and after reduced caloric intake in patients with Gilbert's syndrome. Cholic and chenodeoxycholic acid were determined by radioimmunoassay. In all patients there was a pronounced increase in serum bilirubin (mean increase, 140%) after caloric restriction. However, both fasting and postprandial levels of serum bile acids were within the normal range before and after reduced caloric intake. The results indicate that different mechanisms are involved in the hepatic uptake and secretion of bile acids and bilirubin. Moreover, the results show that determinations of serum bile acids can be used to assess liver function in patients with Gilbert's syndrome irrespective of the degree of hyperbilirubinemia.

Normal fasting-state levels of serum cholyl-conjugated bile acids in Gilbert's syndrome: an aid to the diagnosis

Fasting levels of cholic acid conjugates were determined by radioimmunoassay in the serum of 24 patients with extensively documented Gilbert's syndrome and in 98 healthy controls without unconjugated hyperbilirubinemia. The Gilbert's syndrome patients studied included all three subtypes, as determined from studies of the plasma disappearance kinetics of sulfobromophthalein and indocyanine green. Although patients with structural liver disease severe enough to produce hyperbilirubinemia almost invariably have elevated fasting serum levels of cholic acid conjugates, values were normal in each of the Gilbert's syndrome patients, including patients with metabolic abnormalities in sulfobromophthalein and indocyanine green transport. It is concluded that the measurement of fasting serum levels of cholic acid conjugates is a useful adjunct to the diagnosis of Gilbert's syndrome.

Rotor's syndrome: a study on variations in pigment metabolism with age

The effects of aging on the pigment metabolism in Rotor's syndrome were investigated in six cases examined at least twice at an average interval of 10.5 +/- 6.5 years and additional four cases examined only once. No significant increase was found in the total (TB) or direct (DB) bilirubin in serum. However, indirect bilirubin increased significantly from 1.21 +/- 0.72 mg/dl to 2.28 +/- 1.00 mg/dl (p less than 0.05) and DB/TB ratio (% Direct) decreased significantly from 77.3 +/- 6.6% to 64.4 +/- 8.7% (p less than 0.05). BSP retentions at 45 minutes increased significantly from 26.8 +/- 10.9% to 45.3 +/- 14.9% (p less than 0.05). A significant positive correlation between the values of BSP retained at 45 minutes and the age was also observed (p less than 0.01). These results suggest that the pigment metabolism in Rotor's syndrome deteriorates with the age.

Serum primary bile acids in Gilbert's syndrome

We studied some aspects of bile acid metabolism in 25 patients affected by Gilbert's syndrome, 5 patients with hemolytic anemia, and 25 control subjects in order to assess whether bile acids as well as bilirubin are affected in unconjugated hyperbilirubinemic conditions. We measured serum cholic and chenodeoxycholic acid conjugates fasting and postprandially, the plasma disappearance of intravenously injected cholyl[1-14C]glycine, 14CO2 in breath, and 14C in stools after oral administration of the same isotope. Mean serum fasting level of conjugated cholic acid was significantly reduced in hyperbilirubinemic patients (p less than 0.01) in comparison with the controls, while the postprandial elevation was similar. The cholyl[1-14C]glycine hepatic uptake was faster in the patients with Gilbert's syndrome, but no significant difference was found as far as 14CO2 in breath and 14C in stools were concerned. Additional in vitro studies showed that increasing bilirubin concentrations displace glycocholic acid and, to a lesser extent, glycochenodeoxycholic acid from their binding to albumin, the affinity constant of the latter bile acid being 30 times greater than that of the former one. This competition between bilirubin and bile acids explains the faster hepatic uptake of cholic acid conjugates and hence their lower serum levels in unconjugated hyperbilirubinemic conditions. In addition, low levels of cholic acid conjugates, together with normal serum chenodeoxycholic acid conjugate levels, discriminate Gilbert's syndrome from other causes of hyperbilirubinemia.

A modeling study of the effect of fasting on bilirubin kinetics in Gilbert's syndrome

The mechanism of fasting hyperbilirubinemia (FH) is not fully understood. We investigated basal bilirubin kinetics in 20 Gilbert's patients and in 7 healthy volunteers. The study was repeated in seven of these Gilbert's patients after 48-h fasting. A two-compartment model proved to be adequate for interpreting crystalline bilirubin kinetics in these individuals. The parameters of bilirubin kinetics were estimated by employing a maximum likelihood parameter estimation technique. Consistency of the model and uniqueness of the estimated parameter values (from the covariance matrix) were shown. Our results confirmed previous observations regarding impaired bilirubin kinetics in Gilbert's patients as compared to controls. The main results obtained from kinetic studies in Gilbert's patients after fasting were i) no modification in the bilirubin clearance, and ii) a more than twice increase of bilirubin turnover. These data indicate that FH is related to an increased bilirubin production (mainly intrahepatic). Furthermore, evidence arises from this study that the bilirubin tolerance test is a useful diagnostic test for Gilbert's syndrome.

Effects of corticosteroids on bilirubin metabolism in patients with Gilbert's syndrome

To elucidate the mechanism whereby corticosteroids decrease the serum bilirubin concentration, changes in bilirubin metabolism were studied in patients with Gilbert's syndrome using a bilirubin load test and/or nicotinic acid test before and after corticosteroid treatment. Steroid administration increased hepatic clearance and uptake of bilirubin; the transfer rate for biliary excretion was unaffected. These results suggest that the main effect was enhancement of hepatic uptake or storage of bilirubin, which may be an important mechanism whereby corticosteroids reduce serum bilirubin concentrations in various liver disorders.

[Gilbert's jaundice. Current clinico-nosographic physiopathological and therapeutical aspects. I. Recent findings in Gilbert's syndrome]

Gilbert's icterus is a term used to cover certain forms of free bilirubin hyperbilirubinaemia which occur without any clear signs of hyperhaemolysis and are thus based on a fundamental defect in bilirubin liver cell clearance. Speculatively, this defect may be considered as being located at the level of any one of the steps along the metabolic route of the pigment, between the vascular pole of the liver cell and the microsomes. The incidence of these forms is calculated at about 4-6% of the population, while study of its familial distribution would suggest its inclusion among genetically conditioned metabolic disturbances. Investigations of various groups of patients suggest heredity of poorly penetrating, incomplete expressivity dominant autosomic type. As for pathogenesis, analysis of the formation of glycuronide bilirubin on the part of liver microsomes has shown a frequent reduction in glycuronyltransferase activity in patients with Gilbert's icterus; on the other hand, separation of the two carrier proteins y and z, and kinetic studies with free radiobilirubin, suggest that in certain of these subjects there is an alteration in the liver cell's capacity to take up and hold bilirubin removed from the blood. On the basis of such data, Gilbert's icteruses have been traditionally subdivided into two types: the first, with slight bilirubinaemia, due to an uptaking defect, the second, with higher bilirubin, due to a reduction in glycuronide conjugation. From the morphological viewpoint, the optical microscope does not reveal any outstanding elements in the livers of Gilbert patients; some workers using the electronic microscope have insisted on the not infrequent presence of damage to the vascular pole of the liver cell, which would fall in with the hypothesis of a membrane pathology as the underlying factor in one type of Gilbert's icterus. Numerous granules with lysosome characteristics have also been seen at the biliary pole of the liver cell. Whether these are the cause of the disease or, as would appear more likely, they are only an epiphenomenon secondary to the accumulation of a non-metabolized product of the liver, is still under discussion. Theoretically, therefore, two groups can be distinguished for free bilirubin icteruses of hepatic pathogenesis and thus not only for Gilbert's icterus; those due to a membrane or y and z carrier pathology, and those with microsome pathology due to partial glycuronyltransferase deficiency. The most recent tendency is thus to unify under the common label of a glycuronyltransferase deficiency the type II of Gilbert's icterus and the Crigler-Najjar disease, even though gene transmission modalities differ. Some workers thus suggest two types of Crigler-Najjar disease: type I, the classical type, due to absolute glycuronyltransferase deficiency and type II due to a relative deficiency, taking in the II form of Gilbert's icterus...

Effect of dietary composition on the unconjugated hyperbilirubinaemia of Gilbert's syndrome

The influence of dietary composition on the unconjugated hyperbilirubinaemia of Gilbert's syndrome was studied in 29 patients. After a period on a normal diet (10 MJ) an intravenous infusion of 40% glucose (8-4 MJ) together with a 1-6 MJ oral diet for two days resulted in an increment in plasma bilirubin concentration of 127 +/- 18% (mean +/- SEM) above the basal level. Both the administration of intravenous Intralipid 20% and the return to a normal diet caused a prompt reversal of this glucose effect. An increment of 135 +/- 10% in plasma bilirubin concentration was obtained when a standard "fasting" diet (1-6 MJ) was given for two days. When the lipid content of this "fasting" diet was increased from 33% to 85%, the rise in plasma bilirubin was only 49 +/- 19%. A 10 MJ oral diet for three days, which contained most of its energy content as carbohydrate and only 0-6% as lipid, produced a 76 +/- 12% increase in plasma bilirubin concentration. When the lipid content of the diet was increased to 9% of the energy intake no significant change from the basal level was observed. These findings support the hypothesis that the hyperbilirubinaemia associated with both carbohydrate feeding and fasting is attributable, at least in part, to lipid withdrawal. Although a restricted dietary intake or the parenteral administration of lipid-free solutions has a marked effect on the hyperbilirubinaemia of patients with Gilbert's syndrome, normal daily variation in dietary composition is unlikely to cause a significant change. The influence of different feeding regimes on neonatal hyperbilirubinaemia requires investigation.

Caloric intake and unconjugated hyperbilirubinemia

Reduction in caloric intake was associated with a greater absolute rise in the serum bilirubin concentration in patients with Gilbert's syndrome and partial hepatic bilirubin uridine diphosphate glucuronyltransferase (UDPG-T) dysfunction compared to patients with hemolytic unconjugated hyperbilirubinemia and normal subjects. Two patients with overt hemolysis but an exaggerated response to caloric deprivation had reduced UDPG-T activities comparable to Gilbert's syndrome. The UDPG-T activities in the other patients with hemolytic jaundice were normal. The combination of fasting and novobiocin in 2 normal subjects produced a greater increase in bilirubin level than either fasting or novobiocin alone. These data suggest that theunderlying UDPG-T dysfunction, rather than the prefasting level of unconjugated hyperbilirubinemia, is responsible for the diet-induced hyperbilirubinemia in Gilbert's syndrome. The diet test appears to differentiate Gilbert's syndrome from hemolytic jaundice as well as from normal subjects, irrespective of the initial serum bilirubin concentration.