Allopurinol Metabolism in a Patient

Ann Rheum Dis: first published as 10.1136/ard.42.6.684 on 1 December 1983. Downloaded from Annals ofthe Rheumatic Diseases, 1983, 42, 684-686 Allopurinol metabolism in a patient with xanthine oxidase deficiency HISASHI YAMANAKA, KUSUKI NISHIOKA, TAKEHIKO SUZUKI,* AND KEIICHI KOHNO* From the Rheumatology Department, Clinical Research Centre, Tokyo Women's Medical College, 2-4-1, NS BLD, Nishishinjuku, Shinjukuku, Tokyo, Japan SUMMARY A patient with complete deficiency of xanthine oxidise would not be expected to oxidase allopurinol to oxipurinol if allopurinol did not have any alternative metabolic pathway. 400 mg of allopurinol was administered to a patient with xanthine oxidase deficiency, and plasma allopurinol, oxipurinol, hypoxanthine, and xanthine levels were determined serially by the use of high-perfornman9e liquid chromatography (HPLC). Plasma oxipurinol as well as allopurinol was increased after the administration of allopurinol, and oxipurinol reached a maximum level of 13 1 ,u.g/ml at 6 hours after the administration. This was the same pattern as that of normal controls. This result demonstrated the existence of some other oxidising enzyme of allopurinol than xanthine oxidase. Allopurinol (4-hydroxypyrazolo[3,4-d]pyrimidine) free diet. Creatinine clearance was 73 3 m/min, and is known as a potent inhibitor of xanthine oxidase no calculus was found in her urinary tract by abdomi- copyright. (EC 1.2.3.2). In addition allopurinol itself is nal plain x-ray film and drip infusion pyelography. metabolised in vivo by xanthine oxidase to oxipurinol The xanthine oxidase activity of the duodenal (4,6-dihydroxypyrazolo[ 3,4-d]pyrimidine, which mucosa, which was obtained by gastrofibroscopy, also inhibits xanthine oxidase. A patient with com- was determined by the following procedures. The plete deficiency of xanthine oxidase would not be tissue specimens, weighing 5 to 10 mg, were expected to oxidise allopurinol to oxipurinol in vivo, homogenised in sodium pyrophosphate buffer solu- if allopurinol did not have any alternative metabolic tion (pH 8*0, 0-067 M) and centrifuged at 10 OOOg pathway. In this paper, we report the conversion of for 40 minutes. The supematants were concentrated http://ard.bmj.com/ allopurinol to oxipurinol in a patient with deficiency and then reacted with a reaction mixture (pH 8.0) of xanthine oxidase and discuss the poss'ible containing 0 5 mM of hypoxanthine at 37°C for 30 metabolic pathway. minutes, and the uric acid product was determined by the use of a spectrophotometer at 292 nm. Protein Materials and methods concentrations were determined by the method of Lowry et al.3 was found in this The patient' was a 54-year-old female. She had been No activity of xanthine oxidase on September 24, 2021 by guest. Protected suffering from Graves's disease since she was 36 patient compared with that of a normal control, which years old and had received methimazole continuous- was 15*4 nmo/hour/mg protein. She was diagnosed ly, but there was no history of haematuria, abdominal as having complete deficiency of xanthine oxidase. colicky pain, urinary calculi, or administration of 400 mg of allopurinol was administered orally in allopurinol. Her parents were consanguineous and one dose to this patient. At the same time 150 mg of her sister had chronic thyroiditis. At the age of 49 allopurinol was administered to 2 healthy men whose hypouricaemia was revealed by chance. Her serum serum uric acid levels were within normal limits as the uric acid level was only 0 4 mg/dl (0-02 mmolI). On controls. Plasma samples of this patient and controls the other hand her urinary excretion of oxypurine, were obtained serially by heparinised venous punc- determined by the method of J0rgensen and ture until 25 hours after the administration of Poulsen,2 was as high as 320 mg/day on a purine- allopurinol. Plasma allopurinol, oxipurinol, hypoxanthine and Accepted for publication 7 January 1983. xanthine were determined by the following methods. *Products Formulation Research Laboratory, Tanabe Seiyaku, Osaka, Japan. Allopurinol was commercially obtained from Tanabe Correspondence to Dr K. Nishioka. Seiyaku (Oaska, Japan). Oxipurinol was supplied 684 Ann Rheum Dis: first published as 10.1136/ard.42.6.684 on 1 December 1983. Downloaded from Allopurinol metabolism in a patient with xanthine oxidase deficiency 685 from the same company. Xanthine was obtained Patient with xanthine oxidase deficiency from Sigma (St Louis, Missouri, USA), and hypoxan- ),g/ml I I thine from Kohjin (Tokyo, Japan). Chelex-100 resin 12 Allopur inol / I (200-400 mesh) was obtained from Bio-Rad 400mg Laboratories (Richmond, California, USA). All I 10 'Jl I other chemicals were of analytical reagent grade I commercially available. I * _Oxipurinol P,6 Plasma concentrations of allopurinol, oxipurinol, 8 hypoxanthine, and xanthine were determined by the I method of Suzuki et al. (paper in preparation) by a modified procedure of Brown and Bye.4 6. Chelex-10OCu++ resins were prepared according to the method of Brown et al.,4 packed into glass col- 4 umns (0 6 x 25 cm). and washed with water followed by 002 M carbonate buffer, pH 11 0. Aliquots (0.2 AAllopur inol ml) of plasma were applied to the columns. The col- 2 umns were washed with carbonate buffer, pH 11 0, followed by water, and eluted with 1 M ammonium 0 solution. The eluate was collected in a volumetric hours flask, which contained 0-2 ml of internal standard Normal controls (n=2) pg/ml solution (sodium salicylate), and filled up to 10 ml. Allopur inol The resultant mixture was lyophilised to dryness, and 4 150 mg the residue was then dissolved in 400 ,l of water. A 100 ,ul aliquot of the solution was injected into the 2;;~~~t~~~~~:~~~-52X p1urino high-performance liquid chromatography (HPLC) copyright. system. Chromatography was performed with a 0 39 0 Allopurinol x 30 cm 4Bondapak C18 reversed-phase column 0 2 4 6 8 24 and 0 01 M ammonium phosphate (pH 6.0) as the hours mobile phase. A detector wavelength of 254 nm was Fig. 1 Allopurinol and oxipurinol after the oral used. This method was suitable for analysing adminsistration ofallopurinol. oxypurines in the range of 0-05-20 ,ug in 0-2 ml of plasma. Recoveries of the 4 compounds of interest were 85-95%. Patient with xanthine oxidase deficiency Allopur inol http://ard.bmj.com/ Results pg/ml 3 The plasma allopurinol and oxipurinol of this patient and healthy controls are shown in Fig. 1. In the control group the concentration of plasma allopurinol 2, was highest at 2 hours after the oral administration of Xanthine \ allopurinol and then rapidly decreased. The concen- 1b on September 24, 2021 by guest. Protected tration of plasma oxipurinol was highest at 8 hours after administration of the allopurinol and then 0 decreased gradually. In the patient the maximum 0 2 4 6 8 24 plasma allopurinol level was observed at 14 hours hours after its administration, after which it rapidly Normal controls (n=2) decreased. Oxipurinol increased in the same pattern pg/ml Allopurinol as that of the controls, reaching the value of 13-1 2. 150 mg ,g/ml at 6 hours after administration, of the allo- I Xanthine purinol. Plasma hypoxanthine and xanthine concentrations are shown in Fig. 2. In the controls almost no signifi- ypoxanthine cant change was seen, but in the patient hypoxan- 0 2 4 6 8 24 thine was markedly decreased between 6 and 8 hours hours after the administration of allopurinol, simultan- Fig. 2 Hypoxanthine and xanthine after the oral eously with the peak level of plasma oxipurinol. administration ofallopurinol. Ann Rheum Dis: first published as 10.1136/ard.42.6.684 on 1 December 1983. Downloaded from 686 Yamanaka, Nishioka, Suzuki, Kohno Discussion allopurinol is oxidised by this other enzyme even in normal subjects In connection with the metabolism of allopurinol in Patients with xanthinuria may differ in their the patient with xanthinuria it was of interest to enzyme patterns. Further investigation by direct analyse whether or not some enzyme other than methods will be needed to clarify this. xanthine oxidase might be present. There have been previous reports on the urinary excretion of References allopurinol and oxipurinol when allopurinol was 1 Katsuki T, Shimizu T, Nishina T, Fujihira K, Nishioka K, administered to patients with xanthinuria, but the Ohsawa T. A case of asymptomatic xanthine oxidase deficiency. results conflicted greatly. Various authors5-8 Nippon Naika Gakkai Zasshi 1981; 70: 1263-6. 2 J0rgensen S, Poulsen H E. Enzymatic determination of hypox- reported that alopurinol was excreted unchanged anthine and xanthine in human plasma and urine. Acta Phar- and that oxipurinol was absent in the urine of their macol 1955; 11: 223-43. cases. Others"' observed the conversion of 3 Lowry 0 H, Rosebrough N J, Faff A L, Randall R J. Protein allopurinol to oxipurinol in the urine of their xanth- measurement with the folin phenol reagent. J Biol Chem 1951; 193: 265-75. inuric patients. In view of this finding some enzyme 4 Brown M, Bye A. The determination of allopurinol and that oxidises allopurinol even in the absence ofxanth- oxipurinol in human plasma and urine.J Chromotogr 1977; 142: ine oxidase might be present. Chalmers et al."0 sug- 195-202. gested inosinic acid dehydrogenase (EC 1. 2. 1. 14) as 5 Engelman K, Watts R W E, Klinenberg J R, Sjoerdsma A, Seegmiller J E. Clinical physiological and biochemical studies of this alternative enzyme, but later Nelson et al. 12 took a patient with xanthinuria and pheochromocytoma. Am J Med exception to this because allopurinol ribotide could 1964 37: 839-61. not be a substrate for this enzyme.

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