Gut: first published as 10.1136/gut.7.6.706 on 1 December 1966. Downloaded from

Gut, 1966, 7, 706

International symposium on pigments

An international symposium on bile pigments was 100 ml. In normal human adults (blood bank doners) the held at the Royal Free Hospital, London, on 11 and serum glucuronide concentrations ranged from 12 July 1966. 5 to 25 ,g. per 100 ml. Male donors had significantly higher serum levels than females. ORIGIN OF BILE PIGMENTS B. NOIR (Buenos Aires) presented chromatographic evi- L G. ISRAELS (Winnipeg) produced evidence that the dence which showed that 10 to 15 % of the conjugated bile early labelled fraction of bilirubin which could be demon- pigments was present as bilirubin sulphate. strated using isotopically labelled glycine was composed of two components, one related to erythropoiesis and the E. TALAFANT (Czechoslovakia) studied the nature of other apparently unrelated to erythropoiesis and probably ether-extractable bilirubin in obstructive caused of hepatic origin. by carcinoma. He postulated that this was a complex of bilirubin glucuronide with an unknown lipid substance. S. SCHWARTZ (Minneapolis) emphasized that the early labelled bilirubin fraction probably had many compon- J. D. OSTROW (Cleveland) examined the yellow pigments ents each with its own turnover rate and that this made in bile of the Gunn rat and showed that they could not be quantitation ofeach component all the more difficult. identified with the yellow pigments formed from the photooxidative breakdown of bilirubin. S. H. ROBINSON (Boston) described a new experimental technique for studying the early labelled component of M. JIRSA (Prague) described the isolation from faeces of bilirubin in the ligated of the Gunn rat. Using infants a new which was different from sterco- 14C bilirubin he measured the total miscible bilirubin bilin, i-urobilin, and d-urobilin. pool. In addition, the rate of bile pigment formation following the administration of 2-14C glycine was esti- T. K. WITH (Swendborg) drew attention to the deficien- mated. This allowed precise assessment of bilirubin and cies in our knowledge of what pigments were responsible for the brown haem production. The early labelled peak accounted for colour of normal faeces. Most textbooks http://gut.bmj.com/ 15% of all labelled pigment. Experiments with isolated attributed this to but this is colourless. perfused rat liver showed that the liver was a major The other known bile pigments were unlikely to be re- source of the early labelled pigment. sponsible because they were either colourless or orange. After considerable discussion it became apparent that H. N. NAKAJIMA (Tokyo) described studies of an enzyme no one in the audience knew what pigment was respons- system which could be responsible for the breakdown of ible. haemoglobin to bilirubin.

BILE PIGMENT TRANSPORT on September 23, 2021 by guest. Protected copyright. L. POWELL (London) said that the hyperbilirubinaemia in and obstructive jaundice was aggravated R. SCHMID (Chicago) discussed the physiological im- in most cases by a shortened red cell survival. The cause portance of the binding of bilirubin by albumin. The of this was unknown but studies in rats suggested the tightness of this bond determined the amount of bili- bilirubin glucuronide appeared to play a role whereas rubin which entered the cell. Systemic acidosis and unconjugated bilirubin did not. organic anions, such as salicylate and thyroxine, which compete with bilirubin for the binding sites on albumin, NATURE OF BILE PIGMENTS increased the unbound fraction of bilirubin in the plasma without altering the total body pool of bilirubin. Thus the R. LESTER (Boston) said that the reason why bilirubin factors responsible for bilirubin encephalopathy in the required conjugation before excretion was probably re- newborn were high levels of unconjugated bilirubin, low lated to its steric configuration. Studies with radioactive plasma albumin levels, and the metabolic acidosis which labelled pigments showed that mesobilirubinogen was commonly exists. rapidly excreted without conjugation whereas mesobili- rubin, an intermediate compound resembling bilirubin in G. GRODSKY (San Francisco) had studied bilirubin up- having unsaturated A and C bonds, required conjugation take by the hepatic cell using tritium-labelled bilirubin. before excretion. These studies showed that bilirubin was taken up and concentrated as the free pigment in the rat and that this R. BRODERSEN (Copenhagen) described a radioisotope was not a rate limited process. Bilirubin in the liver was method which would detect concentrations of bilirubin chiefly in the cell sap and was associated with a mac- diglucuronide in the serum in concentrations of 1 ,ug. per romolecule immunologically distinct from albumin. 706 Gut: first published as 10.1136/gut.7.6.706 on 1 December 1966. Downloaded from

International symposium on bile pigments 707 L. M. GARTNER (New York) reported studies ofhormonal of 14C bilirubin and that renal excretion of bilirubin was regulation of the hepatic excretion of bilirubin. There was the main route of its disposal. an hepatic excretory defect in hypophysectomized rats and this was primarily if not entirely due to decreased J. de GROOTE (Louvain) had studied the renal clearance thyroid activity. of conjugated bilirubin in 31 patients with jaundice. The bilirubin clearance was increased in obstructive jaundice A. WHITE (Leeds) studied the distribution of the as compared with parenchymatous jaundice. He postu- glucuronyl transferase of bilirubin and paranitrophenol lated that this might have been due to raised plasma levels in the cell membrane. She concluded that there was no of bile salts which increase the dializability of bilirubin. In glucuronyl transferase activity in the cytoplasmic contrast E. E. OWEN (Florida) could find no significant membrane of the microsomes although this was present difference in renal clearance of conjugated bilirubin in in both rough and smooth . patients with different types of jaundice. He suggested that glomerular filtration was the main mechanism of P. BERTHELOT (Paris) discussed experiments which renal excretion of bile pigments. showed that unconjugated bilirubin could be excreted in small amounts in rat bile. M. ALI (London) presented evidence, from studies using dialysis, infusion ofsubstances which alter protein binding of conjugated bilirubin, and renal tubular inhibitors, that S. SCHENKER (Dallas) showed that there was a bidi- glomerular filteration was the main mechanism for bili- rectional transfer of unconjugated bilirubin via the rubin excretion in the rat. placenta and that this was the primary route of disposal of foetal bilirubin in the monkey. M. FULOP (New York) discussed the possible signific- ance of conjugated bile acids in the renal excretion of bille F. IBER (Baltimore) proposed a model for studying the pigments. He suggested that bile acids acted by displacing kinetics of excretion of 14C-labelled bilirubin in animals the conjugated bilirubin from albumin, thus increasing the with the bile duct ligated. His analysis of the data obtained amount of pigment available for excretion by glomerular in the dog one month after common bile duct ligation filtration. indicated that there was an equilibrium between the production and disposition of bilirubin and that the M. MILNE (London) showed that the urinary excretion disposition occured mainly in the with about 10% of in man was pH dependent. Increased in the stool. urinary urobilinogen was associated with increased pro- duction, increased absorption (as with delayed intestinal

B. H. BILLING (London) analysed the plasma disappear- transit), with hepatobiliary disease, and with heavy http://gut.bmj.com/ ance curves of conjugated and unconjugated 14C bilirubin alkalinization of the urine. All these factors probably in rats with the bile duct ligated. She showed that there played a part in causing the marked diurnal variation in was no inhibition of hepatic uptake or conjugation urinary urobilinogen excretion. on September 23, 2021 by guest. Protected copyright.