Comparison of the biliary excretion of the four isomers of bilirubin-IX in Wistar and homozygous Gunn rats.
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ABSTRACT:
SUBMITTER: Blanckaert N
PROVIDER: S-EPMC1164778 | biostudies-other | 1977 Apr
REPOSITORIES: biostudies-other
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Project description:The kinetics of biliary excretion of the main two photoproducts after injection into Gunn rats were examined. The photoproducts that are obtained from experiments in vitro consist of unknown pigment, photobilirubin IXa and a small amount of (ZZ)-bilirubin IXa. It was confirmed previously that the first two photoproducts are identical with the main two photoproducts obtained in vivo. In experiments on four animals, the average of total biliary recoveries of unknown pigment was 81.4%, and that of photobilirubin IXa in the bile estimated by the Sigma-minus method was 29.8 min and that for unknown pigment was 4.3 min. The rate of thermal reversion of photobilirubin IXa to (ZZ)-bilirubin IXa in the bile at 37 degrees C was very rapid, i.e. its half-life was 6.2 min.
| S-EPMC1163216 | biostudies-other
Project description:On cycled exposure of Gunn rats to total darkness and low and high illumination, biliary excretion rates of (EZ)- and (ZE)-bilirubin and (EZ)-cyclobilirubin increased up to approx. 10-fold from the mean basal values of 1.2 and 0.2 microgram/h to the mean maximum values of 25.2 and 4.2 micrograms/h respectively, and at the same time those of (EE)-bilirubin and (EE)-cyclobilirubin also increased, but at very much lower rates than those of the first-mentioned two. During the low illumination only (EZ)- and (ZE)-bilirubin and (EZ)-cyclobilirubin appeared in the urine; during the high illumination (EE)-bilirubin and (EE)-cyclobilirubin also appeared, showing a similar excretion pattern to that observed in the bile, but the total urinary excretion rates were lower than the total biliary excretion rates. The serum bilirubin concentrations fell gradually to lower values, accompanied by an increment in (EZ)- and (ZE)-bilirubin, but (EZ)-cyclobilirubin was not detected. It is concluded that during phototherapy the predominant pathway for the removal of bilirubin from the body in the Gunn rat is by biliary excretion of the geometric photoisomers (EZ)- and (ZE)-bilirubin, derived from Z----E isomerization, and the structural photoisomer (EZ)-cyclobilirubin, formed from intramolecular endo-vinyl cyclization.
| S-EPMC1144101 | biostudies-other
Project description:1. The biliary excretion of [(14)C]trimophonium iodide [tri[(14)C]methyl(3-hydroxyphenyl)ammonium iodide] was studied in normal Wistar animals and in jaundiced homozygous Gunn rats. 2. In normal Wistar rats small amounts of radioactivity (approx. 3% of the dose in 4h) were excreted in bile as two glucuronide conjugates, i.e. [(14)C]trimophonium glucuronide [tri[(14)C]methyl-(3-oxyphenyl)ammonium glucuronide] (85%) and 3-di[(14)C]methylaminophenyl glucuronide (10-15%). Only minor amounts of the unchanged drug were detected in bile. 3. In the homozygous jaundiced Gunn rat large amounts of radioactivity (26% of the dose in 4h) were eliminated in bile as [(14)C]trimophonium glucuronide alone. The quantitative excretion of this metabolite in Gunn rat bile was about ten times that in normal animals. 4. It is proposed that the biochemical lesion in the homozygous Gunn rat may indirectly affect the biliary transport of exogenous glucuronides across the canalicular membrane.
| S-EPMC1179451 | biostudies-other
Project description:Gunn rats lack bilirubin UDP-glycosyltransferases, but diazo-negative derivatives of bilirubin have been described in their bile. In order to investigate this alternative disposal of bilirubin, crude bile samples from Gunn and Wistar rats were directly analysed by h.p.l.c. Besides bilirubin (in Gunn rats) or its glycosides (in Wistar rats), two major compounds were detected. A yellow one corresponded to the previously documented vitamin B-2 and was equally prominent in Gunn rats or Wistar-rat bile. The other compound was colourless, but on standing in contact with air it was spontaneously oxidized to a pinkish-yellow pigment. It was far more prominent in Gunn-rat bile. Analysis of bile obtained after intravenous injection of [14C]bilirubin to Gunn rats demonstrated that this compound was highly labelled. Freezing and thawing of the bile resulted in the formation of a series of diazo-negative derivatives, demonstrating that the original compound was quite labile. Spectral (adsorption and fluorescent) and chromatographic (h.p.l.c., t.l.c. and paper chromatography) analysis of the oxidized form of the labelled compound allowed its identification as urobilin-i. The colourless compound secreted in bile was urobilinogen-i. Administration of neomycin and bacitracin to Gunn rats or gut resection suppressed the biliary excretion of urobilinogen and thus confirmed its intestinal origin. Urobilinogen seems thus to represent the major bilirubin derivative present in Gunn-rat bile. Its breakdown products might represent the so-far-unidentified diazo-negative polar bilirubin derivatives. Since only a small amount of bilirubin is present in Gunn-rat bile, the urobilinogen formed in the intestinal lumen seems to be derived from bilirubin reaching the gut via routes other than the biliary one.
| S-EPMC1131409 | biostudies-other
Project description:Circulating bilirubin is associated with reduced serum cholesterol concentrations in humans and in hyperbilirubinaemic Gunn rats. However, mechanisms contributing to hypocholesterolaemia remain unknown. Therefore, this study aimed to investigate cholesterol synthesis, transport and excretion in mutant Gunn rats. Adult Gunn and control rats were assessed for daily faecal sterol excretion using metabolic cages, and water was supplemented with [1-13 C]-acetate to determine cholesterol synthesis. Bile was collected to measure biliary lipid secretion. Serum and liver were collected for biochemical analysis and for gene/protein expression using RT-qPCR and western blot, respectively. Additionally, serum was collected and analysed from juvenile rats. A significant interaction of sex, age and phenotype on circulating lipids was found with adult female Gunn rats reporting significantly lower cholesterol and phospholipids. Female Gunn rats also demonstrated elevated cholesterol synthesis, greater biliary lipid secretion and increased total faecal cholesterol and bile acid excretion. Furthermore, they possessed increased hepatic low-density lipoprotein (LDL) receptor and SREBP2 expression. In contrast, there were no changes to sterol metabolism in adult male Gunn rats. This is the first study to demonstrate elevated faecal sterol excretion in female hyperbilirubinaemic Gunn rats. Increased sterol excretion creates a negative intestinal sterol balance that is compensated for by increased cholesterol synthesis and LDL receptor expression. Therefore, reduced circulating cholesterol is potentially caused by increased hepatic uptake via the LDL receptor. Future studies are required to further evaluate the sexual dimorphism of this response and whether similar findings occur in females with benign unconjugated hyperbilirubinaemia (Gilbert's syndrome). KEY POINTS: Female adult hyperbilirubinaemic (Gunn) rats demonstrated lower circulating cholesterol, corroborating human studies that report a negative association between bilirubin and cholesterol concentrations. Furthermore, female Gunn rats had elevated sterol excretion creating a negative intestinal sterol balance that was compensated for by elevated cholesterol synthesis and increased hepatic low-density lipoprotein (LDL) receptor expression. Therefore, elevated LDL receptor expression potentially leads to reduced circulating cholesterol levels in female Gunn rats providing an explanation for the hypocholesterolaemia observed in humans with elevated bilirubin levels. This study also reports a novel interaction of sex with the hyperbilirubinaemic phenotype on sterol metabolism because changes were only reported in females and not in male Gunn rats. Future studies are required to further evaluate the sexual dimorphism of this response and whether similar findings occur in females with benign unconjugated hyperbilirubinaemia (Gilbert's syndrome).
| S-EPMC9310728 | biostudies-literature
Project description:1. Reconstitution of purified bilirubin UDP-glucuronyltransferase from Wistar-rat liver into Gunn-rat liver microsomes provides a better environment than phosphatidylcholine liposomes, such that the final specific activity of the Wistar-rat liver enzyme was increased up to 85 units/mg of protein. 2. Gunn- and Wistar-rat liver microsomes were equally effective for reconstitution of the purified enzyme. 3. The transferase activity does not appear to be fully expressed in the more rigid environment of foetal Wistar-rat liver microsomes. 4. These reconstitution experiments reveal a final specific activity for the purified bilirubin UDP-glucuronyltransferase consistent with the capacity of the whole rat liver to glucuronidate bilirubin and indicate that the absence of this enzyme activity in Gunn-rat liver microsomes is not due to an abnormal microenvironment.
| S-EPMC1163694 | biostudies-other
Project description:Bilinoid pigments in bile of homozygous Gunn rats (jj) were analysed either after formation of dipyrrolic ethyl anthranilate azo derivatives or as the unmodified parent tetrapyrroles. 1. T.l.c. of the azo derivatives revealed seven major unconjugated components which were structurally characterized by chemical tests, spectrophotometry and mass spectrometry. In addition, two minor components were identified as azodipyrrole (A+B)-glucoside and azodipyrrole (A+B)-beta-d-glucuronide. 2. Extraction and t.l.c. of the tetrapyrrolic pigments showed 13 major yellow diazo-positive bands. Four of them, accounting for 59% of total diazo-positive material, were identified as unconjugated bilirubin-IXalpha, -IXbeta, -IXgamma and -IXdelta. A fifth band (16%) was characterized as a mixture of two isomeric monohydroxyl derivatives and another band (8%) as a dihydroxyl derivative of bilirubin-IXalpha. 3. Although unconjugated bilirubin-IXalpha constitutes one-third of total diazo-positive material in bile of our strain of Gunn rats, the daily amount excreted represented only about 3-4% of daily bilirubin production. 4. Phototherapy caused a 2.2-fold increase in the biliary output of diazo-positive bilinoids, but did not affect markedly their composition. However, an additional diazo-negative pigment, accounting for one-third of total yellow colour, was observed but was not identified. Mass-spectral data on two dipyrrolic azopigments have been deposited as Supplementary Publication SUP 50076 (3 pages) with the British Library Lending Division, Boston Spa, Wetherby, W. Yorkshire LS23 7BQ, U.K., from whom copies may be obtained on the terms given in Biochem. J. (1977) 161, 1.
| S-EPMC1164779 | biostudies-other
Project description:The bilrubin-IXalpha conjugates in bile and the activities of bilirubin-IX alpha--UDP-glycosyltransferases in liver and kidney were determined for ten species of mammals and for the chicken. 1. In the mammalian species, bilirubin-IX alpha glucuronide was the predominant bile pigment. Excretion of neutral glycosides was unimportant, except in the cat, the mouse, the rabbit and the dog, where glucose and xylose represented 12--41% of total conjugating groups bound to bilirubin-IX alpha. In chicken bile, glucoside and glucuronide conjugates were of equal importance. They probably represent only a small fraction of the total bile pigment. 2. The transferase activities in liver showed pronounced species variation. This was also apparent with regard to activation by digitonin, pH optimum and relative activities of transferases acting on either UDP-glucuronic acid or neutral UDP-sugars. 3. Man, the dog, the cat and the rat excrete bilirubin-IX alpha largely as diconjugated derivatives. In general, diconjugated bilirubin-IX alpha could also be synthesized in vitro with liver homogenate, bilirubin-IX alpha and UDP-sugar. In contrast, for the other species examined, bilirubin pigments consisted predominantly of monoconjugated bilirubin-IX alpha. Synthesis in vitro with UDP-glucuronic acid, UDP-glucose or UDP-xylose as the sugar donor led exclusively to the formation of monoconjugated bilirubin-IX alpha. 4. The transferase activities in the kidney were restricted to the cortex and were important only for the rat and the dog. No activity at all could be detected for several species, including man. 5. Comparison of the transferase activities in liver with reported values of the maximal rate of excretion in bile suggests a close linkage between conjugation and biliary secretion of bilirubin-IX alpha.
| S-EPMC1164854 | biostudies-other
Project description:Bilirubin neurotoxicity has been studied for decades and has been shown to affect various mechanisms via significant modulation of gene expression. This suggests that vital regulatory mechanisms of gene expression, such as epigenetic mechanisms, could play a role in bilirubin neurotoxicity. Histone acetylation has recently received attention in the CNS due to its role in gene modulation for numerous biological processes, such as synaptic plasticity, learning, memory, development and differentiation. Aberrant epigenetic regulation of gene expression in psychiatric and neurodegenerative disorders has also been described. In this work, we followed the levels of histone 3 lysine 14 acetylation (H3K14Ac) in the cerebellum (Cll) of the developing (2, 9, 17 days after the birth) and adult Gunn rat, the natural model for neonatal hyperbilirubinemia and kernicterus. We observed an age-specific alteration of the H3K14Ac in the hyperbilirubinemic animals. The GeneOntology analysis of the H3K14Ac linked chromatin revealed that almost 45% of H3K14Ac ChiP-Seq TSS-promoter genes were involved in CNS development including maturation and differentiation, morphogenesis, dendritogenesis, and migration. These data suggest that the hallmark Cll hypoplasia in the Gunn rat occurs also via epigenetically controlled mechanisms during the maturation of this brain structure, unraveling a novel aspect of the bilirubin-induced neurotoxicity.
| S-EPMC6135864 | biostudies-literature
Project description:1. The biliary excretion of injected [(14)C]aniline, [(14)C]benzoic acid, 4-amino-hippuric acid and 4-acetamidohippuric acid in six or eight species of animal (rat, dog, hen, cat, rabbit, guinea pig, rhesus monkey and sheep) was studied. 2. These compounds, with molecular weights in the range 93-236, are poorly excreted in the bile in all the species examined and, in effect, there is little significant species difference in the extent of their biliary excretion. 3. Compounds of higher molecular weight (355-495) were also studied, namely succinylsulphathiazole, [(14)C]stilboestrol glucuronide, sulphadimethoxine N(1)-glucuronide and phenolphthalein glucuronide. 4. With these compounds a clear species difference in the extent of biliary excretion was found, the rat, dog and hen being good excretors, the rabbit, guinea pig and monkey poor excretors, and the cat and sheep taking an intermediary position. 5. There was a general trend for biliary excretion to be higher in all species when the compounds were of higher molecular weight. 6. These results are discussed in their relation to species differences in drug metabolism.
| S-EPMC1198453 | biostudies-other