Gut 1996; 38: 864-869

Assessing the site of increased intestinalpermeability in coeliac and inflammatory boweldisease

K Teahon, S Somasundaram, T Smith, I Menzies, I Bjarnason

AbstractBackground-The precise site of intesti-nal permeability changes in patients withcoeliac and inflammatory bowel disease isunknown.Aims-To design a non-invasive techniquefor the localisation ofaltered gastrointesti-nal permeability to slchromium labelledEDTA (51CrEDTA). The method dependson comparing and defining concentration/time profiles in serum of a series ofsimultaneously ingested indicators witha well defined absorption site (3-0-methyl-D-glucose (jejunal indicator), 57cobaltlabelled vitamin B12 (ileal indicator), andsulphasalazine (caecal-colonic indicator))in relation to simultaneously ingested51CrEDTA.Subjects-Five normal controls, sixpatients with untreated coeliac disease,five with Crohn's ileitis, and five withpan-ulcerative colitis underwent study,which entailed the simultaneous ingestionofthe above four test substances followed,during the next 24 hours, by timed serialcollection of urine and serum for markeranalysis.Results-Urinary excretion of 51CrEDTAwas significantly increased in all patientgroups. Analysis of serum appearancesand profiles of the markers suggested thatthe increased intestinal permeation of51CrEDTA took place in the diseasedjejunum in patients with coeliac disease,predominantly in the ileum in Crohn'sdisease and in the colon in the patientswith pan-ulcerative colitis.Conclusion-A new non-invasive tech-nique has been assessed that permits thelocalisation of the site of permeabilitychanges with the gastrointestinal tract.(Gut 1996; 38: 864-869)

Keywords: intestinal permeability, intestinal function,coeliac disease, inflammatory bowel disease, Crohn'sdisease, ulcerative colitis.

Non-invasive tests of intestinal permeabilityare widely used to screen for small intestinaldisease and assess the importance of theintestinal barrier function in the aetiology andpathogenesis of intestinal and systemicdisease.1 2 Choice of test procedure for assess-ing intestinal permeability depends on clinicaland experimental circumstances. In generalthere is good agreement between resultsobtained with the five hour differential urinary

excretion of lactulose/L-rhamnose (or lactu-lose/mannitol) and the 24 hour urinaryexcretion of 51chromium labelled EDTA(51CrEDTA).2-4 After ingestion the uptake oftest sugars, which are subjected to rapid bac-terial degradation after reaching the caecum,being largely from the small intestine is notaffected by colonic pathology. In the case of51CrEDTA given by itself, distinction betweensmall intestine and colonic contributions to the24 hour urinary excretion is uncertain.

In an attempt to discriminate betweenchanges in small intestinal and colonic per-meability Jenkins et al 5 administered lactulose,L-rhamnose, and 51CrEDTA together andmeasured timed excretions of these markers inurine. The ratio of urinary lactulose/L-rham-nose during the first five hours provided anindex of small intestinal permeability, and thetotal 24 hour urinary excretion of 51CrEDTA,less that of lactulose (as % of doses) servedas an index of colonic permeability.5 Theresults showed that the colon was likely to bethe site of increased intestinal permeation of51CrEDTA in patients with active pan-ulcerative colitis,5 and others have foundsimilar changes after abdominal radiation.6Nevertheless the technique does not permit theadditional differentiation between an upperand lower small intestinal site of altered intesti-nal permeability that is possible using the tech-nique we now report, based on serumconcentration/time profiles after ingestionof 51CrEDTA together with 3-0-methyl-D-glucose, 57Cobalt labelled vitamin B12(57CoVitBI2), and sulphasalazine, which serveas indicators of absorption site.

Methods

Basis of test procedureThe principle of the test was to compare theserum concentration/time profiles of threeabsorption indicators, selected because each isspecifically absorbed from a defined regionwithin the intestinal tract, with that of simul-taneously ingested 51CrEDTA, which should,in theory, permit assessment of the mainintestinal site of 51CrEDTA permeation. Theindicators used were 3-0-methyl-D-glucose,absorbed from the jejunum by an active carriermediated transport system shared with D-glucose and D-galactose,7 vitamin B12, specifi-cally absorbed as a complex with intrinsicfactor by carriers in the ileum,8 and sulpha-salazine, which is metabolised by the azo-reductase of bacteria in the caecum and colon

Department of ClinicalPharmacology,Wolfson Unit,University ofNewcastle upon TyneK Teahon

Department of ClinicalBiochemistry, King'sCollege School ofMedicine andDentistry, LondonS SomasundaramT SmithI MenziesI Bjamason

Correspondence to:Dr K Teahon, Departmentof Gastroenterology,Nottingham City Hospital,Hucknell Road, NottinghamNG5 1PB.Accepted for publication7 December 1995

864

Site of increased intestinal permeability

to yield 5-aminosalicylic acid and sulphapyri-dine.9 The first appearance of 3-0-methyl-D-glucose, 57CoVitBl2 and sulphapyridine inserum should therefore indicate the arrival ofthe 'head' of the test solution after oral admini-stration in the jejunum, ileum, and caecum,respectively, provided that the rate of mucosaluptake is similar for each of the indicators.9The subsequent serum concentrations/timeprofiles are determined by the same factorsthat influence the pharmacokinetic profile ofan ingested drug, namely the site and relativeefficiency of mucosal uptake, the rate ofintestinal transit, metabolic degradation (forsulphapyridine), volume of systemic distribu-tion and rate of clearance. Because of thenature of the test most of these factors applyequally to all the test substances. However, asrenal function is an important determinator ofthe permeation profiles glomerular filtrationrates were assessed during each test.

SubjectsFive healthy volunteers acted as controls (fourmales, one female, mean age 37 years, range22-58). Six symptomatic, newly diagnosedpatients with coeliac disease (four males, twofemales, mean age 42 years, range 32-56), fivepatients with Crohn's ileitis of activity indexover 15010 (four males, one female, mean age29 years, range 20-42), and five patients (allmales, mean age 44 years, range 26-59) withactive pan-ulcerative colitis as defined byTruelove et al 1 were studied.

All the patients with inflammatory boweldisease had sufficiently severe disease activityto warrant hospital admission. Three werereceiving 5-aminosalicylic acid. The studieswere carried out before treatment was changedand no patient was receiving corticosteroids orimmunosuppressants. Disease location inpatients with inflammatory bowel disease hadbeen established but was confirmed bycolonoscopy, radiology or 1 indium leucocytescintigrams, or all three, within a week of thesestudies.The reliability of 'first appearance in serum'

to indicate arrival at a particular level in theintestine requires that mucosal uptake of themarkers used is not unduly delayed and takesplace at a similar rate. The rates of mucosalpermeation for 57CoVitBI2 and sulphapyridinehave been assessed previously.8 9 12 To assessthe relative mucosal permeation rates of 3-0-methyl-D-glucose and 51CrEDTA in the sameintestine four patients (males, mean age 38years, range 32-40) with the irritable bowelsyndrome, undergoing routine gastroduo-denoscopy, had a test solution containing 3-0-methyl-D-glucose (2.5 g) and 51CrEDTA (1mCi) in 50 ml water instilled directly into theduodenum. Serum samples taken before, andat five minute intervals for a period of 30minutes after instillation, were assayed forthese markers.No subject had recently had alcohol (within

seven days), non-steroidal anti-inflammatorydrugs or other drugs (within six months)known to affect intestinal integrity.2

These studies were approved by the Harrowand Camberwell Health Authority EthicalCommittees and all subjects gave informedconsent.

ProcedureAll subjects were admitted to a metabolicresearch ward for the study. They fasted from12 hours before the test until the study wascomplete. Throughout the studies they laysupine except for toilet purposes. At 7 am onthe day of the test subjects received an intra-muscular injection of cyanocobalamine (1 mgin 1 ml, Glaxo, UK) to saturate vitamin B12receptors and hence to facilitate the detectionof 57CoVitBI2 in serum. An indwelling intra-venous cannula was placed into the ante-cubital veins of both arms, one being used forintravenous injection and fluid replacement(started at 11 am; 3 litres of glucose-salinewith 60 meq potassium given over 18 hours)and the other for obtaining blood samples foranalyses.At 7.45 am subjects swallowed two capsules

containing human intrinsic factor (AmershamInternational, Amersham, Buckinghamshire,UK and Frost Laboratories, Quebec, Canada)with 20 ml of water. At exactly 8 am patientsreceived 10 ml of sterile saline intravenouslycontaining 100 ,uCi 99mtechnetium diethylene-triaminopenta acetate (99mTcDTPA) (3.7MBq, Amersham International) over a periodof 10 seconds while drinking the 100 ml testsolution (within one minute), which con-tained: 3-0-methyl-D-Glucose (2.5 g, Sigma,Poole, Dorset, UK), 57CoVitB12 (5 ,uCi, 19kBq, Amersham International), sulphasalazine(2.0 g, Syrup, Pharmacia, Milton Keynes,UK), 51CrEDTA (1 mCi, 37 MBq, AmershamInternational).Ten ml of blood was obtained before the

test, at five minute intervals for the first 30minutes, at one hour, hourly until 8 pm andtwo hourly until completion of the test at 8 amthe next morning. A complete 24 hour urinarycollection was made.The radiation dose received during the test

is less than 1.5 mSieverts.

Marker analysesTo ensure precision the 99mTcDTPA,57CoVitBI2, and 51CrEDTA doses for inges-tion were all weighed. The blood samples wereallowed to clot, spun down, and the serumcollected. Exactly 1-0 ml of each serum sampleand 5 ml of urine was counted along withstandards on a LKB 1280 or 1282 gamma-counter along with appropriate standards. The99mTc was counted on the day of the test. Oneweek later, when all 99mTc activity haddecayed, the samples and standards werecounted for 57Co and 51Cr, appropriatecrossover corrections being made.To calculate glomerular filtration rates the

99mTc disappearance data in serum was plotted(% dose/litre) on a logarithmic scale and thelinear part of the slope extrapolated to the yaxis. The intercept value divided into 100%

865

Teahon, Somasundaram, Smith, Menzies, Bjarnason

Time offirst appearance of test markers in serum and glomenularfiltration rates

Patient numbers

Normal controls Coeliac disease Crohn's disease Ulcerative colitis

1 2 3 4 5 1 2 3 4 5 6 1 2 3 4 5 1 2 3 4 5

3-0-m-D-glucose 20 10 15 10 5 10 30 10 5 60 20 5 10 10 10 10 5 15 10 10 1051CrEDTA 30 60 60 60 25 5 30 20 5 60 10 10 15 10 60 15 60 60 10 15 2057CoVitB12 240 300 300 180 300 120 240 360 180 300 180 300 240 120 240 300 300 240 180 240 360Sulphapyridine 180 180 240 300 300 180 240 360 300 420 240 180 240 120 240 420 360 240 240 120 300GFR (mllmin) 121 135 112 113 123 131 105 108 97 110 119 127 111 101 116 134 102 118 94 115 129

and multiplied by 1000 ml gives the extracellu-lar volume distribution of99mTcDTPA (in ml).This is then multiplied by X, which is the slopeof the linear part of the 99mTcDTPA disap-pearance plot, and this gives the glomerularfiltration rate (mllmin).13Serum 3-0-methyl-D-glucose was measured

by thin layer chromatography and densitome-try as previously described14 and sulphapyri-dine by high pressure liquid chromatographywith ultraviolet detection'5 both of which havesatisfactory accuracy and precision, coeffi-cients of variation ranges being 3-5-8% and4-1 1%, respectively.

StatisticsStatistical significance between patient groupswas assessed by Wilcoxon's rank sum test.

ResultsThe rest was well tolerated by all except onenormal subject who had severe nausea andvomiting, starting six hours after start of thetest and coinciding with the rise in the serumsulphapyridine value.

Appearance of markers in serum and renalfunctionDetectable values of both 3-0-methyl-D-glucose and 51CrEDTA appeared in serum atthe same time after instillation into the duo-denum, at five minutes in three patients withirritable bowel syndrome, and at 10 minutes inthe fourth.

o 3-0-Methyl-D-glucose

* Sulphapyridine, Vitamin B12

* 51CrEDTA

In the main study serum creatinine wasnormal in all subjects. The Table shows thatglomerular filtration rates varies from 94ml/min to 138 ml/min, which is within thereported normal physiological range for theseage groups, and there were no significant dif-ference between the study groups.The Table shows the time of first appear-

ance of 3-0-methyl-D-glucose, 51CrEDTA,57CoVitB12 and sulphapyridine in serum afteroral administration. While there is some vari-ation between different people in the time offirst appearance of each marker, there was nosignificant (p>0.3) difference between patientgroups except for the appearance of51CrEDTA. Appearances of 3-0-methyl-D-glucose precedes that of 51CrEDTA in boththe normal and ulcerative colitis groups(p<005), but no significant difference wasfound in the time of appearance of these twomarkers in the serum of patients with coeliacand ileal Crohn's disease.The appearance of 57CoVitB12 preceded

that of sulphapyridine in eight subjects, but inseven subjects these markers appeared at thesame time, and in the remaining six the 'caecal'marker preceded the 'ileal' marker. The gastricto caecal transit time was usually in the rangeof three to six hours and did not differ signifi-cantly between the groups.

Permeation profilesThe summation permeation profiles (mean(SEM)) from the four different groups areshown in Figures 1-4.

Figure 1 shows the permeation profile forthe normal group. Peak levels of 51CrEDTA(less than 0046% of the dose/litre in eachcase) are achieved one to two hours (in onecase 51CrEDTA peaked at six hours) after theappearance of 3-0-methyl-D-glucose, butbefore the appearance of the 'ileal' and 'caecal'markers. Insignificant serum values of51CrEDTA were found between eight and 14hours after starting the test, and only onenormal subject had detectable values through-out the 24 hour period. The mean 24 hoururinary excretion of 51CrEDTA was 2.13(0 31)%, range 1*46 to 3.15%.

Figure 2 shows the permeation profile fromthe patients with untreated coeliac disease.Comparison with normal subject response(Fig 1) shows that there are no significant dif-ferences in the profiles (or serum peak values)of the 'jejunal', 'ileal', or 'caecal' markersexcept that the 3-0-methyl-D-glucose peak at120 minutes instead of 30 minutes.51CrEDTA appears earlier, and reaches a

10

0)

a)0)0cl

TimeFigure 1: Permeation profiles from normal subjects. Vertical axis shows the % dose/litre ofthe test substances in serum (on a logarithmic scale) over 24 hours after their simultaneousingestion.

866

Site of increased intestinal permeability8

0

0

1.0

ao

Time

Figure 2: Permeation profiles from patients with untreated coeliac disease. Symbols as inFigure 1.

(L)

a)

0

0

._

Time

Figure 3: Permeation profiles from patients with Crohn's ileitis. Symbols as in Figure 1.~~~~~~~~~~~;T0.01

0 2 4 6 8 10 12 14 16 18 20 22 24

Time

Figure 4: Permeation profiles from patients with pan-ukerative colitis. Symbols as inFigure 1.

significantly higher peak value than normal incoeliac disease (>0.08% dose/litre in eachcase, p<0.01) and at a similar time as 3-0-methyl-D-glucose (in five of six cases).However, as in normal subjects only one

patient had measurable serum 51CrEDTA at14 hours. The urinary excretion of 51CrEDTA(3.61 (0.10)%, range 3.29 to 4.02%) was

significantly greater than in normal subjects.Figure 3 shows the permeation profile from

the patients with Crohn's ileitis. There is an

early rise of 51CrEDTA (in two cases indistin-guishable from that seen in the patients withcoeliac disease), but a second increase ranging

from 0.06 to 0.21% dose/litre and coincidingwith the appearance of the 'ileal' and 'caecal'markers in the serum, was also evident in fourof five patients. Unlike the normal and coeliacdisease groups, significant levels of 51CrEDTAwere detected in serum of the Crohn's ileitisgroup throughout the test. The 24 hoururinary 51CrEDTA excretion, 5.32 (0.98)%,range 2-94 to 831%, was significantly greater(p<001) than in normal subjects.

Figure 4 shows the permeation profile frompatients with pan-ulcerative colitis. The earlypeak values of 51CrEDTA in serum at onehour did not differ significantly from thenormal group (one patient had increased earlyserum values of 51CrEDTA similar to that incoeliac disease). There was, however, a clearincrease in 51CrEDTA values two to fivehours after the appearance of the 'ileal' and'caecal' markers, which was evident in all thepatients. The 24 hour urinary 51CrEDTAexcretion, 5.97 (1.05)%, range 3.06 to 8.85%,was significantly greater than in normalsubjects (p<0.01).

Presenting the mean permeation profiles canbe slightly misleading because of the variationin transit times, etc. In particular the differencebetween individual cases of Crohn's diseaseand ulcerative colitis were sharper than Figures3 and 4 would imply. Figure 5 shows represen-tative traces from a patient with Crohn's ileitisand ulcerative colitis where the increase inserum values of 51CrEDTA clearly coincideswith the appearance of the 'ileal' and 'caecal'markers in Crohn's disease and comes distinc-tive later in ulcerative colitis.

DiscussionThis paper describes a new technique that wasdesigned to assess the site of permeabilitychanges within the gastrointestinal tract. Theresults suggest that the site of increased intesti-nal permeability in coeliac disease, Crohn'sdisease, and pan-ulcerative colitis is the dis-eased intestine itself. In the context of thisstudy there are, however, a number of factorsthat need to be considered when interpretingthe data. In particular the use of the time ofappearance of indicator substances in serumand the permeation profiles is determined by anumber of variables that could affect theresults. These variables include the site, rate,and amount of marker permeating across theintestine, gastric emptying, intestinal dilutionand transit times, metabolism in the case ofsulphapyridine, distribution volume, and renalfunction. However, because the test substanceswere given at the same time the influence ofsome of these factors apply equally to all thetest substances. Thus gastrointestinal dilutionaffects all the markers to a similar extent, andgastric emptying (time to appearance of 3-0-methyl-D-glucose) and small intestinal transittimes (time difference between 3-0-D-glucoseand sulphapyridine) can be calculated andwere not found to be significantly differentbetween the patient groups. Also the mode andrate of renal excretion is similar for all themarkers apart from sulphapyridine, which is

867

868 Teahon, Somasundaram, Smith, Menzies, Bjarnason

10 rA

0)

0.1

0.010 2 4 6 8 10 12 14 16 18 20 22 24

10 BB

.) 1

0)0-0 0.1

0.010 2 4 6 8 10 12 14 16 18 20 22 24

Time

Figure 5: Comparison ofprofilesfrom an individual patient with Crohn's ileitis (A) andulcerative colitis (B). The increase in serum values of51CrEDTA coincides with andfollows the appearance of 'ileal' and 'caecal' markers in Crohn's disease and ulcerativecolitis, respectively. Symbols as in Figure 1.

subjected to hepatic metabolism. It is therate of permeation across the intestine thatdetermines how accurately the 'first appear-ance' of the markers in serum represents the'head' of the test solution in each part of theintestine. There was no discrepancy betweenthe rate of appearance of 3-0-methyl-D-glucose and 51CrEDTA after duodenal instilla-tion in normal subjects and previous studieshave also shown that sulphapyridine appearswithin six minutes of caecal instillation.9 Ourresults, however, show an inconsistencybetween the time of appearance of the 'ileal'and 'caecal' markers in serum and in six casessulphapyridine appeared before the 'ileal'marker. These findings are consistent withreports of a 30-240 minute delay for theappearance of vitamin B12 after ileal instilla-tion,8 12 which is probably due to intra-cellular processing of the vitamin B12 intrinsicfactor complex.16 17 The 'first appearance' of57CoVitBI2 in serum is therefore likely to over-estimate the time it takes for the 'head' of thetest solution to reach the ileum.

In both normal subjects and patients withulcerative colitis there is a significant lag timebetween the serum detection of 3-0-methyl-D-glucose and 51CrEDTA whereas the appear-ance of both markers in the serum after directinstillation into the duodenum is both rapidand simultaneous. This might suggest that themain site of permeation of 51CrEDTA afteringestion is normally somewhat distal to that of3-0-methyl-D-glucose, but it might also bethat the uptake of 51CrEDTA on reaching theduodenum in the 'head' of the test solutiongives serum values that are initially below the

detection limits of the gamma counting.Reliable detection of 51CrEDTA in serummight therefore be delayed until the bulk of thetest solution had entered the jejunum.

In patients with untreated coeliac disease theappearance of 5 CrEDTA in serum coincidedwith and peaked at the same time as 3-0-methyl-D-glucose suggesting that there wasincreased intestinal permeability in the uppersmall intestine. These findings are consistentwith results of studies in coeliac disease, whichindicate increased in vitro permeation of vari-ous markers'8 19 and with freeze fracturestudies,20 which demonstrate decreased strandnumber and depth in the intercellular junc-tions. The results in Crohn's disease were notas clear cut. A similar pattern of increased per-meation of 5'CrEDTA coinciding with that of3-0-methyl-D-glucose was found in twopatients. One of these and the remainingthree patients had peak values of 51CrEDTAcoinciding with the appearance of the 'ileal'and 'caecal' markers. As this rise (seen in Fig5) in the serum values of 51CrEDTA occurredmuch earlier than in the patients with ulcera-tive colitis it seems likely that it representsincreased ileal permeability to 51CrEDTA.Increased 'jejunal' permeability in somepatients with Crohn's ileitis is consistent within vitro findings of increased permeability inapparently unaffected jejunal mucosa ofpatients with Crohn's disease. 19 The initialserum profiles of 5'CrEDTA in pan-ulcerativecolitis were indistinguishable from normalsubjects in four of five cases. The increase inserum 51CrEDTA in the four patientsoccurred somewhat later than in the patientswith Crohn's ileitis, occurring after the appear-ance of the 'ileal' and 'caecal' indicators. Thissuggests that the inflamed colonic mucosa isthe site of increased permeation of 51CrEDTAin ulcerative colitis as suggested by Jenkinset al.5 This is also in keeping with studies show-ing increased permeation of 51CrEDTA afterrectal administration in ulcerative colitis.2' 22Indeed, the permeation of 51CrEDTA cor-related significantly with histopathologicalassessment of disease activity in thesepatients.2'

In summary a new non-invasive techniquehas been assessed that permits the localisationof the site of altered permeability with the gas-trointestinal tract. The principle of the methodseems to be generally applicable to other testsubstances than permeability probes, but thereis a need to identify an equally site specific'ileal indicator' to that of vitamin B12, whichdoes not have the delayed rate of absorption.

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4 Maxton DG, Bjarnason I, Reynolds AP, Catt SD, Peters TJ,Menzies IS. Lactulose, 51 GrEDTA, L-rhamnose andpolyethylene glycol 400 as probe markers for 'in vivo'assessment of human intestinal permeability. Clin Sci1986; 71: 71-80.

Site of increased intestinal permeability 869

5 Jenkins AP, Nukajam WS, Menzies IS, Creamer B.Simultaneous administration of lactulose and 51 Cr-ethy-lenediaminetetraacetic acid. A test to distinguish colonicfrom small-intestinal permeability change. Scand JfGastroenterol 1992; 27: 769-73.

6 Qvist H, Somasundaram S, Macpherson A, Menzies IS,Giercksky K, Bjarnason I. The effect of pelvic irradiationon small and large intestinal absorption and permeabilityin man. Gastroenterology 1994; 106: A430.

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10 Best WR, Becktel JM, Singleton JW, Kern F. Developmentof a Crohn's disease activity index. Gastroenterology 1975;70: 439-44.

11 Truelove SC, Witts U. Cortisone in ulcerative colitis. Finalreport on a therapeutic trial. BMJ 1955; 2: 1041-8.

12 Doscherholmen A, Hagen PS. Delay of absorption of radio-labelled cyanocobalamine in the intestinal wall in the pres-ence of intrinsic factor. J Lab Clin Med 1959; 54: 434-9.

13 Chandler C, Garnett ES, Parsons V, Veall N. Glomerularrate measurement in man by the single injection methodusing 51CrEDTA. Clin Sci 1969; 37: 169-80.

14 Menzies IS, Mount JN, Wheeler MJ. Quantitative estima-tion of clinically important monosaccharides in plasma by

rapid thin layer chromatography. Ann Clin Biochem 1978;15: 65-76.

15 Chungi VS, Gurvinder SR, Shargel L. A simple and rapidliquid chromatographic method for the determination ofmajor metabolites of sulphasalazine in biologic fluids. 7Pharm Sci 1989; 78: 235-8.

16 Peters TJ, Hofbrand AV. Absorption of vitamin B 12 by theguinea pig. I subcellular localisation ofvitamin B12 in ilealenterocyte during absorption. Br J Haematol 1970; 19:369-82.

17 Jenkins WI, Empsow R, Jewel DP, Taylor KB. The subcel-lular localisation of vitamin B 12 during absorption inguinea pig ileum. Gut 1982; 22: 617-23.

18 Bjamason I, Peters TJ. In vitro determination of intestinalpermeability: demonstration of a persisting defect inpatients with coeliac disease. Gut 1984; 25: 145-50.

19 Dawson DJ, Lobley RW, Burrows PC, Notman JA,Mahon M, Holmes R. Changes in jejunal permeabilityand passive permeation of sugars in intestinal biopsies incoeliac disease and Crohn's disease. Clin Sci 1988; 74:427-31.

20 Madara JL, Trier JS. Structural abnormalities of jejunalepithelial cell membranes in coeliac sprue. Lab Invest1980; 43: 254-61.

21 Rask-Madsen J, Schwartz M. Absorption of 51CrEDTA inulcerative colitis following rectal instillation. Scand JGastroenterol 1979; 5: 361-8.

22 O'Morain C, Abelon AC, Chervli LR, Fleischner GM,Das KM.51CrEDTA a useful test in the assessment ofinflammatory bowel disease. J Lab Clin Med 1986; 108:430-5.