kenapa gout seringnya di sinovial

Annals of the Rheumatic Diseases, 1981, 40, 70-74

Plasma and synovial fluid as solvents formonosodium urateROBERT W. DORNER, TERRY D. WEISS, ANDREW R. BALDASSARE,TERRY L. MOORE, AND JACK ZUCKNERFrom the Division ofRheumatology, Saint Louis University School ofMedicine, 1402 South Grand Boulevard,Saint Louis, Missouri 63104, USA

SUMMARY In-vitro differences in monosodium urate (MSU) crystal dissolution in paired plasmaand synovial fluid samples from patients with various arthritides were studied. Plasma was a signi-ficantly better solvent for MSU than synovial fluid (overall difference 6'3 mg/dl (0 37 mmol/l);significant at P

Plasma and synovial fluid as solvents for monosodium urate 71

method8 which employs a lyophilised hyalurinidase-buffer mixture to avoid sample dilution. However,sterile tubes were used and the hyaluronidaEe-buffersolution was sterilised by Millipore filtration prior tolyophilisation. Control tub.s containing onlyJyophilised buffer were prepared similarly. Hyalu-ronidase-treated and control samples were thensubjected to MSU solubility studies as describedabove. Preliminary experiments confirmed theefficacy of hyaluronidase treatment by viscosimetryas previously described.8To test the reproducibility of these procedures

aliquots of a plasma sample from a healthy volunteerand aliquots of a synovial fluid pool from patientswith large effusions were subjected to urate solu-bility determination on 5 separate occasions by theprocedures outlined above. The mean dissolvedurate in plasma was 8 *2 mg/dl (0*49 mmol/l)with a standard deviation of 0 43 (0 -026) or 50%.Corresponding values for synovial fluid were 7-8(0 46), 0 31 (0 002) or 4% respectively. Forcomparison the uricase method itself in our handsgives replications with a standard deviation of about3% around the mean. Presumably similar confidencelimits are applicable to the data obtained on theexperimental samples which were not available insufficient quantities to permit multiple determina-tions.

Results

The amounts of MSU dissolved in paired samples ofplasma and synovial fluid from 32 patients withvarious arthritides under standardised conditionsare shown graphically in Fig. 1. The data have beenseparated according to the primary diagnosis of thedonor of the samples. Under the heading 'Other'patients with inflammatory arthropathies other thanrheumatoid arthritis or gout were included. None ofthem had infectious arthritis. The data show thatplasma (left-hand column in each category) wasalmo3t always a better solvent for MSU than syno-vial fluid (right-hand column in each category).The mean differences as well as the statisticalsignificance limits by t test for paired samples, areshown in Table 1. All the mean differences werestatistically significant as usually defined at the95% confidence limit. Patients with gout showed alesser mean difference and a lower confldence limitthan the overall mean, while patients with osteo-arthritis showed the largest mean difference.An attempt was made to explain the solubility

differentials between plasma and synovial fluid onthe basis of differences in total protein content. Fig. 2is a scatter plot relating MSU solubility to totalprotein concentration of plasma and synovial fluid.

The correlation lines were obtained by least-squaresfitting of the experimental points. The correlationcoefficient for synovial fluid only was r=0-265(no significant correlation), that for plasma onlyr=0-056 (no significant correlation), and that for alldata combined r=0*364 (significant at the 0*01confidence level). The latter ob3ervation is notmeaningful in the absence of significant correlationsin the 2 subgroups.

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Fig. 1 Amounts ofMSU dissolved in paired samplesofplasma and synovial fluid under standardised invitro conditions. The data are separated according todiagnosis: RA= rheumatoid arthritis; OA =osteoarthritis; other= other inflammatory arthritides.In each disease category the left-hand column (a)represents plasma urate levels, the right-hand column(0) synovial fluid urate levels. Members ofa pair areconnected with a line. SI conversion: Urate mmol/l=mg/dl x 0-0595.

Table 1 Mean differences of the amount ofMSUdissolved in plasma and in synovial fluid (pairedsamples) from patients with various arthritidesNumber Diagnosis Mean Statisticalof difference significancespecimens (mg per di) (P less than12 Rheumatoid arthritis 7.1 0-017 Osteoarthritis 9-5 0-016 Gout 3.8 0-027 Other inflammatory

arthropathies 3 *9 0.0532 All patients combined 6-2 0-001SI conversion: Urate mmol/l=mg/dl x 0 0595.

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72 Dorner, Weiss, Baldassare, Moore, Zuckner

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Fig. 2 Relation of MSU solubi,ity to total proteinconcentration. The graph represents a scatter plotrelating the quantity ofMSU dissolved in plasma (e)or synovial fluid (0) under standardised in-vitroconditions to the total protein concentration of thesolvent. The correlation lines were obtained by least-squares fitting. PL-plasma; SF-synovial fluid, PL +SF= all data combined. SI conversion: Urate mmol/l=mg/dl x 0 0595; protein g/l=g/dl x JO.

The amounts of MSU dissolved in hyaluronidase-treated and control synovial fluids from patientswith various arthritides are shown graphically inFig. 3. Again the data have been separated accordingto diagnosis. They show that in most cases hyalu-ronidase-treated synovial fluid is a better solventfor MSU than buffered control fluid. The mean

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Fig. 3 Amounts ofMSU dissolved in hyaluronidase-treated and control synovial fluids. The data areseparated according to diagnosis (see legend to Fig. 1).In each disease category the left-hand column (0)represents urate levels of synovialfluid treated withbuffer only (37VC), 4 hr), the right-hand column (CH)those after hyaluronidase treatment under the sameconditions, prior to MSU solubility studies understandardised conditions. Corresponding hyaluronidase-treated and control sanmples are connected with a line.SI conversion: Urate mmol/l=mg/dl x 0 0595.

differences, as well as their statistical significanceby t test for paired samples are shown in Table 2.The overall mean difference for all patients wassignificant at the 99% confidence limit. Significantdifferences were also found for the patients withrheumatoid arthritis and those with gout, while thedifference for patients with other inflammatoryarthritides was not significant. The number ofosteoarthritis patients included was too small topermit meaningful statistical analysis.

Table 2 Mean differences of the amounts ofMSUdissolved in hyaluronidase-treated and control synovialfluid (paired samples) from patients with variousarthritidesNumber Diagnosis Mean Statisticalof difference significancespecimens (mg per dl) (P less than)7 Rheumatoid arthritis 4.2 0.0112 Gout 1.9 0.052 Osteoarthritis 48 -7 Other inflammatory

arthropathies 2-0 not significant28 All patients combined 2.2 0.01

SI conversion: Urate mmol/1= mg/dl x 0*0595.


Plasma and synovial fluid as solvents for monosodium urate 73DiscussionMSU crystals found in synovial fluid and otherconnective tissues of patients with gout form animportant aspect of all accounts of pathogenesis ofthe acute gouty attack.'-4 However, why MSUshould be selectively deposited in these tissues isnot fully understood. Explanations involving the pHdifferential between plasma and the synovial fluidin an involved joint have been discredited.49Temperature differentials between joint spaces andthe systemic circulation exist10 and have beenconsidered as a possible cause of MSU crystaldeposition." Urate-binding proteins'2 13 and pro-tein-polysaccharidesl415 have been described, buttheir significance is not clear.We have undertaken to study in vitro the ability

of plasma and synovial fluid, obtained simul-taneously from patients with various arthritides,to dissolve microcrystalline MSU. Our data showthat plasma is a better solvent for MSU than syno-vial fluid. The differential may be sufficient to explaincrystallisation of MSU in synovial fluid at uratelevels which do not exceed the solubility in plasma.It can be estimated from published data2 '0 thatthis differential is greater by a factor of 3 than thesolubility differential due only to temperaturedifferences between joints and blood. Both factorsmay be of importance. Once local supersaturationexists, the phenomenon of nucleationl6 is of greatimportance in the actual crystallisation process.Normal synovial fluid has frequently been likened

to an ultrafiltrate of plasma. Grossly, there are 2principal differences between the 2 fluids.'7 (i)Synovial fluid has less than half as much totalprotein as plasma; (ii) synovial fluid contains about03y% hyaluronate while plasma contains no morethan traces. We explored the possibility that thesolubility differences ofMSU in plasma and synovialfluid might be related to these gross compositionaldifferences.A good case can be made for the influence of

protein concentration on urate solubility, sinceKlinenberg and his associates2 have already shownthat increasing concentrations of albumin enhanceurate solubility proportionately. Our attempts atcorrelating MSU solubility with total proteinconcentration in plasma and synovial fluid showeda tendency toward increased solubility at higherprotein concentration, but the correlation did notreach statistical significance.The influence of high molecular weight hyalu-

ronate has been explored by comparing hyalu-ronidase-treated and control samples of synovialfluid. Hyaluronidase treatment was found toenhance the ability ofsynovial fluid to dissolve MSU.

Since the patient populations used in comparingplasma versus synovial fluid and hyaluronidase-treated versus control synovial fluids were not thesame, it is not possible to decide unequivocallywhether the presence of highly polymerised hyalu-ronate in synovial fluid is sufficient to account forthe differential in MSU solubility between plasmaand synovial fluid. It appears that only about halfthe plasma versus synovial fluid differential can beexplained by the effect of hyaluronate. The possi-bility that low molecular weight fragments ofhyaluronate might have an effect on urate solubilityhas not been excluded. The data presented are hardto reconcile with the work of Katz,15 who found aurate-solubilising proteoglycan which is destroyedby hyaluronidase in synovial fluid. Our data arecompatible with Laurent's18 excluded space concept,but the observed solubility differential is greaterthan what one might have predicted on the basis ofLaurent's data.

Since MSU solubility is specifically a problem inpatients with gout, it was of interest to compare theresults obtained on samples from gouty patientswith those from patients with other forms of arth-ritis. One might have expected the solubility dif-ferential between plasma and synovial fluid to beparticularly large in patients with gout. This was notfound to be true. The mean solubility differentialfor gouty patients was lower than that found in mostother diseases. Similarly, the solubility change afterhyaluronidase digestion was smaller than average; infact 2 of the 3 synovial fluids in which hyaluronidasetreatment did not enhance MSU solubility were frompatients with gout. The significance of these findingsis not clear at present.

We thank Mrs Claudia Barnes Cuca for the carefullyexecuted technical work.

References' Seegmiller J E. The acute attack in gouty arthritis.

Arthritis Rheum 1965; 8: 714-23.2 Klinenberg J R, Bluestone R, Schlosstein L, Waisman J,Whitehouse M W. Urate deposition disease. How is itregulated and how can it be modified? Ann Intern Med1973; 78: 99-111.

s McCarty J D, Kozin F. (1975). An overview of cellularand molecular mechanisms in crystal-induced inflam-mation. Arthritis Rheum 1975; 18: 757-64.

4 Spilberg 1. Current concepts of the mechanism of acuteinflammation in gouty arthritis. Arthritis Rheum 1975; 18:219-34.

5 McCarty D J, Faires J S. A comparison of the durationof local anti-inflammatory effect of several adreno-corticosteroid esters-a bioassay technique. Curr TherRes 1963; 5: 284-90.

6 Praetorius E, Poulson H. Enzymatic determination ofuric acid. ScandJ Clin Lab Invest 1953; 5: 273-80.

7 Lowry 0 H, Rosebrough N S, Farr A L, Randall R J.


74 Dorner, Weiss, Baldassare, Moore, ZucknerProtein measurement with the Folin phenol reagent.J Biol Chem 1951; 193: 265-75.

8 Dorner R W, Gantner G E, Uddin J, Zuckner J. The useof ultrasound in synovial fluid analysis. Arthritis Rheum1965; 8: 368-75.

9Wilcox W R, Khalaf A, Weinberger A, Kippen I,Klinenberg J R. Solubility of uric acid and monosodiumurate. Med Biol Eng 1972; 10: 522-31.

10Horvath S M, Hollander J L. Intra-articular temperatureas a measure of joint reaction. J Clin Invest 1949; 28:469-773.Loeb J H. The influence of temperature on the solubilityof monosodium urate. Arthritis Rheum 1972; 15: 189-92.

12 Alvsaker J 0. Uric acid in human plasma. IV Investi-gations of the interaction between urate and macro-molecular fractions from healthy individuals and patients

with diseases associated with hyperuricemia. Scand JClin Lab Invest 1965; 17: 476-82.

13 Alvsaker J 0. Uric acid in human plasma. V. Isolationand identification of plasma proteins interacting withurate. Scand J Clin Lab Invest 1966; 18: 227-39.

14 Katz W A, Schubert M. The interaction of monosodiumurate with connective tissue components. J Clin Invest1970; 49: 1783-9.

15 Katz W A. Deposition of urate crystals in gout. ArthritisRheum 1975; 18: 751-6.

18 Wilcox W R, Khalaf A A. Nucleation of monosodiumurate crystals. Ann Rheum Dis 1975; 34: 332-9.

17 Hamerman D, Rosenberg L C, Schubert M. Diarthrodialjoints revisited. J Bone Joint Surg 1970;- 52A: 725-74.18 Laurent T C. Solubility of sodium urate in presence of

chondroitin-4-sulfate. Nature 1964; 202: 1334.


solvents for monosodium urate.Plasma and synovial fluid as

and J ZucknerR W Dorner, T D Weiss, A R Baldassare, T L Moore

doi: 10.1136/ard.40.1.701981 40: 70-74 Ann Rheum Dis

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kenapa gout seringnya di sinovial

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