In~. J. N.ucJ. Med. S.iQ~. Vol. 12. No.5. pp. 357-362. 1985Printed m Great Britain. All rights reserved

0047-0740/85 53.00 +0.00Copyright © 1985 Pergamon Press Ltd

Species of 67Ga-binding AcidMucopolysaccharide in Liver

ATSUSHI ANDO· and ITSUKO ANDO

The School of Allied Medical Professions Kanazawa Un iversity 5 11 80 K d, • ' .. - t 0 atsuno,Kanazawa CIty 920, Japan

(Received 25 July 1985)

It was determine~ fro,m '!leasuring neutral saccharide in the structure that the principal 67Ga-bindin acidmu~opolysacchaTlde m hver was keratan sulfate and/or keratan polysulfate, On the other hand, r. wasclarified from the results of mucopolysaceharase treatment that the main 67G bi di idI haride i I' , a- in 109 aCI muco -po ysacc an e In rver was not either one of keratan sulfate heparan sulfate heparin ch d iti I'A B d C Ba d h . ' " on rot In su late

, an . se on t e present results. It was deduced that the main 67Ga b' di idpolysaccharide in liver was keratan polysulfate, - m 109 aCI muco-

Materials and Methods

Concerning the species of 67Ga-binding acid muco­polysaccharides, we(4,6) deduced that 67Ga was boundto .acid mucopolysaccharide (e.g. keratan sulfate)which contained no uronic acid. Furthermore, wel l3)

reported that this acid mucopolysaccharide is keratanpolysulfate. The present paper describes the details of67Ga-binding acid mucopolysaccharide species inliver.

Materials

Normal male Wistar rats weighing 153-186 g.Carrier-free 67Ga-citrate (100--200 #lCi/mL) was

prepared from 67Ga-citrate (Daiichi RadioisotopeLaboratories Ltd, Japan) and 0.08 M sodium citratesolution. Carrier-free sodium sulfate-t'S solution, pH6.0-8 .0 (1 mL containing 900 #lCi) , was preparedfrom H2SOc

3sS in 0.05 M HCI solution (JapanAtomic Energy Research Institute, Japan) and 0.1 NNaOH solution to the osmotic pressure at which thissolution can be injected intravenously into the ani­mals.

Pronase E (protease from Streptomyces griseus,Kaken Chemical Co., Japan).

The following ten biochemical materials werepurchased from Seikagaku Kogyo Co. Ltd, Japan:chondroitinase ABC (from Proteus vulgaris), hepa­ritinase (from Flavobacterium heparium), Keratanase(from Pseudomonas), heparinase (from Flavobacte­riumheparium), chondroitin sulfate A, Na-salt (fromwhale cartilage), chondroitin sulfate B, Na-salt (frompig skin), chondroitin sulfate C, Na-salt (from sharkcartilage), heparan sulfate, Na-salt (from bovine kid-ney), heparin, Na-salt (from pig intestine), keratansulfate, Na-salt (from bovine cornea).

357

• Author for correspondence,

Introduction

It was concluded by us'" that the chemical bondsof 67Ga, I II In and '6~b (the elements of group III inthe periodic table) were not of the chelate ring typeto the thiol radicals, but that all were ionic bonds tothe sulfonic groups, the phosphoryl radicals and thecarboxyl radicals in the body, and that binding ofthese elements to body constituents was performedby an ion-exchange reaction to some of the aboveradicals, except the thiol radical. Furthermore, we(21presumed that 67Ga, Il1 ln and 169Yb were bound toacid mucopolysaccharides, because the concentrationof these nuclides was predominant in connectivetissue (especially inflammatory tissues) rather thanin viable tumor tissues, regardless of the time afteradministration, and because connective tissue (es­pecially infla~matory tissues) contained largeamounts of acid mucopolysaccharides which hadmany sulfonic groups and carboxyl radicals in theirstructures. Ando'" originally determined that 67Ga

169" •Il1ln and . I b were bound to the acid mucopoly-saccharides in two species of tumor tissues d~hrlichtumor and Yoshida sarcoma). It was also reported byAndo et aJ.l4-6) that a 67Ga-binding acid mucopoly­saccharide had been separated by cellulose acetateelectrophoresis from tumor and liver lysosome, andthat 67Ga-binding acid mucopolysaccharides in tumorand liver were very similar. It was also reported byusl7.8) that IlIln, 169Yb and 167Tm were bound to thesame acid mucopolysaccharide that 67Ga was boundto. Later, these results of ours were supported by thein vitro study of Kojima et al.,(9) and by reports thath~paran sulfate (a kind of acid mucopolysaccharide)mtght be an acceptor for 67Ga accumulation.oG-12)

358 A TSUSHI ANDO and ITSUKO ANDO

Sephadex G-50 (particle size 50-150 II), G-l00(particle size 40-120 P. Pharmacia Fine ChemicalsAB, Sweden).

Dowell. I-X2 (Cl type, anion-exchange resin, TheDow Chemical Co.• U.S.A.)

Incubation time with Pronase E

One of the rats from above group was injectedintravenously with 67Ga-citrate (0.4 mL) and waskilled 24 h later. The liver was excised and rinsed in0.9% NaCI solution. All manipulations describedbelow were conducted at 4°C. The liver was homo­genized with 10vol of 0.15 M KCI containing0.01 M Tris buffer, pH 7.6 in a Potter-Elvehjem typehomogenizer. The homogenates were centrifuged for15min at 400g and the sediments were discarded.The mitochondrial fraction (Iysosomes were con­tained in this fraction) was collected from thehomogenates by centrifuging at 5000g for 15min.This mitochondrial fraction (from I g of liver) wassuspended homogeneously in 2.8 mL of the abovebuffer solution. The suspension was divided into7 mL-aliquots. The fivesuspensions (7 mL each) wereadjusted to pH 7.8-8.2 with 0.1 M NaOH and wereincubated with 60 mg of pronase E at 37°C.

After digestion of 12h, one of the reaction mix­tures was centrifuged at 3000 rpm (1500g) for20 min, and the sediments were discarded. Five milli­Iitres of the supernatant was applied to a column ofSephadex G-IOO (1.2 x 75cm) that had been equili­brated with 0.15 M NaCI containing 0.1 M aceticacid-sodium acetate buffer, pH 5.0. The radioactivitywas eluted with 120mL of the same buffer. The flowrate was 0.3 mL/min. Three millilitre fractions werecollected to measure radioactivity, uronic acids, pro­teins and sialic acids. During cont inuous incubation,pH (7.8-8.2) adjustment and the addition of 30 mgpronase E were carried out to each of the other fourreaction mixtures every 24 h. Each was eluted in tumevery 24 h by the same procedure described above.Radioactivity of 67Ga, proteins. uronic acids andsialic acids in the eluates were measured by methodsdescribed below.

Neutral saccharide in acid mucopolysaccharide

The reaction mixture, which was incubated for 60 hby the above described procedure, was applied to acolumn of Sephadex G-50 (1.2 x 65 em) that hadbeen equilibrated with 0.15 M NaCI containing 0.1 Macetic acid-sodium acetate buffer, pH 5.0. The radio­activity was eluted with 120mL of the same buffer.The flow rate was 0.4 mL/min. Three millilitre frac­tions were collected to measure radioactivity, uronicacids, and proteins.

The void volume was divided into two equal parts.One was eluted through a Sephadex G-I 00 column bythe same procedure described above. The other wastreated with 10% trichloroacetic acid solution (TCA),and proteins were precipitated by centrifugation at3000rpm for 10min. The supernatant was eluted

through a Sephadex G-IOO column by the sameprocedure described above. Radioactivity of 670a,neutral saccharides. proteins and uronic acids in theeluates were measured by the methods describedbelow.

Digestion with mucopolysaccharase

Chondroitinase ABC treatment. In the case of therat treated with 67Ga-citrate, the eluates (fractionnumbers 18-20) of the second peak from the Sep,hadex G·IOO column (Fig. I), to which the pronaseE treated sample of liver had been applied, were putinto the flask and digested with mucopolysaccharaseby the methods described below. Namely. the ob­tained eluate was divided into two equal parts. Mix­tures of chondroitin sulfate A, Band C (2 mg) wasadded to each, and both solutions were adjusted topH 8.4 with 0.1 N NaOH. Chondroitinase ABC(0.83 U/0.4 mL of 0.1% bovine serum albumin solu­tion) was added to one solution, and 0.4 mL of thisalbumin solution was added to the other. Bothsolutions were incubated for 60 min at 37°C. Afterdigestion, both reaction mixtures (5 mL aliquots)were applied separately to a column of SephadexG-50 (1.2 x 65 em), and were eluted by the sameprocedure described above. Radioactivity of 670a anduronic acids were measured.

Heparitinase treatment. The eluates (fraction num­bers 18-20 of Fig. 1) were put into the flask anddivided into two equal parts. Heparan sulfate (I mg)and 3.3mM calcium acetate solution (1.5 mL) wereadded to each, and both solutions were adjusted topH 7.0 with 0.1 N NaOH. Heparitinase (10 U;O.4mLdistilled water) was added to one solution and dis­tilled water (0.4 mL) was added to the other. Bothsolutions were incubated for 60 min at 43°C. Afterdigestion, both reaction mixtures were treated by thesame procedure described for chondroitinase ABC.

lIeparinase treatment. The eluates (fraction num­bers 18-20 of Fig. 1) were put into the flask anddivided into two equal parts. Heparin sodium(1.5 mg) and 3.3 mM calcium acetate solution(1.5 mL) were added to each, and both solutions wereadjusted to pH 7.0 with 0.1 N NaOH. Heparinase(20 U/0.4 mL distilled water) was added to one solu­tion and distilled water (0.4 mL) was added to theother. Both solutions were incubated for 60 min at35°C. After digestion, both reaction mixtures weretreated by the same procedure described for chon­droitinase ABC.

Keratanase treatment. The eluates (fraction num­bers 18-20 of Fig. I) were put into the flask anddivided into two equal parts. Keratan sulfate (1.5 mg)was added to each, and both solutions were adjustedto pH 7.4 with 0.1 N NaOH. Keratanase (6 U/0.6 mLof distilled water) was added to one solution anddistilled water (0.6 mL) was added to the other. Bothsolutions were incubated for 60 min at 37°C. Afterdigestion, both reaction mixtures were eluted bythe same procedure described for chondroitinase

"Ga-binding acid mucopolysaccharide in liver 359

Fig. 1. Sephadex 0-100 chromatography profiles of liverdigested with pronase E at 37°C for 36 h.

ABC. Rad ioactivity and neutral saccharides weremeasured.

Results

Incubation time with pronase E

On centrifugation after digestion with pronase E,40-60% of 61Ga rema ined in the supernatant. FigureI indicates the gel filtration of the supernatant whichwas incubated with pronase E for 36 h. As previouslyreported by US,(6) the first peak (fraction numbers9-13) of 61Ga was eluted in the void volume, thesecond peak (fraction numbers 17-21) was elutedwith the substances with molecular weights of about10,000, and the third peak (fraction numbers 27-34)was eluted with low molecular weight substances. Thefirst, second, and third peaks in the eluates from theSephadex G-IOO column contained 2.9-4.3%,18.4-21.1% and 37.1-51.8% of the applied 61Ga,

respectively. The relation between the incubationtime and the elution rates(%) of61Ga in each peak areshown in Table I. As shown in this Table, the elutionrates for the first peak decreased with the lapse ofincubation time, but those for the second peaksincreased with time and reached approximately 25%of the total radioactivity within 60 h. Based on thedata presented here, it was deduced that 61Ga-bindingacid mucopolysaccharide in the second peak plays themost important role as the 61Ga-binding substance inliver.

•uc:

"'"~..'"et

15 20 25 30 35Fraction number

• n Ga aCIIYlty

:

_ 35S aCIIYlly

& Orcinol mtlhod j...ll\a Lowry'l melhod

C Thiabarb llurlc aCId

1\ ,/~j- \---." i · \\~ I'~- ppro..a.~~r\~

" • \ P \~

# \ \ ~\ ~

~

~u

"S!..."ll:

Separation with anion-exchange resin

Homogenation and digestion. The above rat wasinjected intravenously with sodium sulfate-s'S solu­tion (0.4 ml.) and the liver was excised 24 h afteradministration. The liver was treated by the samemethod, as that used for the rat to which 61Ga-citrate

had been administered. Radioactivity of 3SS in theeluates was also measured. In the case of the rattreated with sodium sulfate-PS, the eluates of thesecond peak (fraction numbers 18-20 of Fig. I)obtained by Sephadex G·IOO filtration were appliedto a Dowex I-X2 column (1.2 x 35 em), The radio­activities of 3SS were fractionated by stepwise elutionwith 100mL of 0.5, 1.25, 1.5, 2.0, 3.0, 4.0 and 5.0 MNaCI solution. Eluate samples were collected in afraction collector and assayed for 3SS by the methoddescribed below.

Measurement

Radioactivity of 61Ga in the eluates was measuredby a well-type scintillation counter (Aloka, JOC-70t)and that of 3SS was measured by a liquid scintillationcounter (Aloka, LSC-673). Protein was determinedby the method of Lowry et al.( 4

) Uronic acids (uronicacids are contained in acid mucopolysaccharides withthe exception of a few species) were measured by theorcinol reaction,'!" Sialic acids (sialic acids are con­tained in the carbohydrate chain of glycoprotein)were assayed by the thiobarbituric acid method,'!"Neutral saccharides (neutral saccharides are con­tained in keratan sulfate and keratan polysulfate)were assayed by the anthrone method.v"

Neutral saccharide in acid mucopolysaccharide

Figure 2 shows the Sephadex G-IOO chromato­graphy profiles of samples treated and untreated withTCA . In the case of the untreated samples, the 67Gapeak (fraction number 19) was ident ical with thepeaks for the neutral saccharide (anthrone method)and proteins (Lowry's method). By TCA treatment,most of the protein was eliminated, and 67Ga wasreleased from the acid mucopolysaccharide andeluted with the low molecular weight substances. Butthe neutral saccharide was eluted in the same frac­tions as those seen for the case of the sample un­treated with TCA .

From these results, it is obvious that 67Ga is boundto the acid mucopolysaccharide which contains neu­tral saccharide in large quantities, and that 67Ga isreleased from the acid mucopolysaccharide by acidi­fying with TCA. Since the sulfated acid mucopoly­saccharides in mammalian tissues which contain neu-

Table I. Relationship between irlcubation time and elution rates(%) of "Ga in each peak of Sephadex G·IOOchromatography. Two

experiments were carried out for each incubation time

Incubation time First peak Second peak Third peak(h) (%) (%) (%)

12 11.5 17.3 48.19.8 20.7 45.6

36 2.9 18.4 51.84.3 21.1 37.1

60 2.5 25.1 45.41.6 25.5 45.9

84 0.4 26.4 63.82.2 25.7 52.1

108 0.3 26.2 63.70.3 25.3 67.3

360 ArsUSHI Axoo and trsexo Axoo

Treated wIth TCA

o lowry', methodNaC!

O.SM J.2SM I.SM 2.0M 3.0M 4.0M S.OM

0.3"1. 37.2% 11.9% 25.5% 5.6% 1.5% 2.0%

Table 2. Elution rates (%) of lSS (sulfated acid muco­polysaccharides) on anion-exchange resin (Dowex I-X2)

columns

it is clear that the 67Ga-binding acid mucopoly­saccharide is an acid mucopolysaccharide other thanheparan sulfate, heparin, and chondroitin sulfate ABand C. '

eeeo...0c:

353025201510

• lI7Ga actlYity

.. Anthrone mtlhad

Fig. 2. Sephadex 0·100 chromatography profiles of thesamples treated and untreated with TeA.

Not treated with TCA

•-'\h~\·.1

If ..\"~I \.'I: \\~ ~~ ...\Q.Q4.a' ~

•ueZis...0c:

Separation with anion-exchange resin

The elution rates of sulfated acid rnucopojy,saccharides-PS on anion-exchange resin columns areshown in Table 2. Of lIS-activities applied to theanion-exchange resin column, 0.3, 37.2, 11.9, 25.5,5.6, 1.5 and 2.0% were eluted with 0.5, 1.25, 1.5, 2.03.0, 4.0 and 5.0 M NaCI, respectively . It was con~c1uded from the cited references'P'!" that 3$S-activitieseluted with 1.25, 1.5, 2.0, 3.0, 4.0 and 5.0 M NaCIindicated heparan sulfate , chondroitin sulfate (orkeratan sulfate), heparin (or keratan sulfate), keratansulfate (or keratan polysulfate) and keratan poly­sulfate.

tral saccharide as a substitute for uronic acid arekeratan sulfate and keratan polysulfate, it is deducedfrom these results that the 67Ga-binding acid muco­polysaccharide is keratan sulfate and/or keratanpolysulfate.

Digestion with mucopolysaccharase

Figure 3 shows the profiles of the sample treatedwith keratanase and the untreated control. In the caseof the sample treated with this enzyme, 67Ga-bindingacid mucopolysaccharide (fraction numbers 9-15)was eluted almost quantitatively without digestionwith this enzyme, although keratan sulfate (anthronemethod) was completely digested by it. In the case ofthe untreated control, 67Ga-binding acid mucopoly­saccharide and keratan sulfate were eluted withoutdigestion as a matter of course.

From these results, it is obvious that the 67Ga_binding acid mucopolysaccharide is not keratan sul­fate. Furthermore, Fig. 3 shows profiles of the sam­ples treated with heparitinase, chondroitinase ABC,and heparinase, respectively, and the untreated con­trols. In the case of the samples treated with hepa­ritinase, chondroitinase ABC, and heparinase,67Ga-binding acid mucopolysaccharides (fractionnumbers 9-15) were eluted almost quantitativelywithout digestion with these enzymes, although thecorresponding acid mucopolysaccharides (orcinolmethod) were completely, or almost completely di­gested by them. In the case of the untreated controls,67Ga-binding acid mucopolysaccharide and addedacid mucopolysaccharides were eluted without di­gestion as a matter of course. From these results,

Discussion

Ando'" had first reported that 67Ga was bound tothe acid mucopolysaccharides in two species of tumortissues. It was also reported by Ando et a/.14

,6) that theprincipal 67Ga-binding acid mucopolysaccharide intumor and liver was the acid mucopolysaccharide(e.g. keratan sulfate) which contained no uronic acidin its structure. Recently we(ZO) showed that 67Ga Wasbound to the acid mucopolysaccharide (keratan SUl­fate, keratan polysulfate) containing no uronic acidin abscess, kidney, heart, lung and spleen. Sasaki etal.,/IO) Kojima et al., (II) and Hama et al. l ll ) supportedour results by the belief that 67Ga would be bound toacid mucopolysaccharide (heparan sulfate) in tumorand in several other tissues. But we think that the67Ga-binding acid mucopolysaccharide species in Softtissues is keratan polysulfate, based on the presentresults and on the cited references. In the case ofkeratan sulfate, the sulfate-to-hexosamine ratio isclose to 1.0, and oversulfated keratan sulfate (thesulfate-to-hexosamine ratio is above 1.0) is calIedkeratan polysulfate. Concerning digestion withmucopolysaccharase, it is known that keratan poly­sulfate is not digested with keratanase, althoughkeratan sulfate is digested with enzyme. Consideringthe results of the experiments on the neutral saCCha­ride which 67Ga-binding acid mucopolysaccharidecontains in its structure, it is concluded that this acidmucopolysaccharide is keratan sulfate and/or kera­tan polysulfate. On the other hand, it is obvious fromthe results of keratanase treatment that this acidmucopolysaccharide is not keratan sulfate. Based onthe data presented here, it is deduced that the

67Ga-binding acid mucopolysaccharide in liver 361

II>UCe.c...o...c«

302520

.~

j". \ "\ I ~\

l \'\ '~ ., ~

...1$

10 15 20 25 30

Control, not treoted with heporitinose

'\~I\·.TGa activit,

!\ 0 Orcinol mlthod

ft': \I \ 1\I I

;. \ .1/ " \

Sample treated with heparitinose

10 15 20 25 30

N\ :nGa atllvlt,

Anthronl mllhodI~

il\ \Jr b.~ \, ~ ...~,,-

10 15 20 25 30

Froction

Control. not treated with kerotanose

Sample treated with keratano5e

Sample treated with chondroitinase ABC Sample trealed with hepartnase

Control. not treatedwith chondroitinose ABC

II>UCe.c...o...c«

30

Control, not treoted with heparinase

I\th \ • 'TGo aCllvlt,

I I 0 Orcinol method

I

1/'\ \! "

30

30

25

25

l"l, \I \

! 'I ~I I

, Ij I

20

20

15

10

1\

I\i \

I..

1\ . I1Go octlvlI,l' 0 OrCinol mllhod

! \I I

I '.J \

'. '

"'"­>­oCI

CI..<:J..

Fraction number

Fig. 3. Sephadex G-SO chromatography profiles of samples treated with mucopolysaccharase and theuntreated controls.

67Ga.binding acid mucopolysaccharide is keratanpolysulfate . Furthermore it is obvious that we musteliminate heparan sulfate. heparin. chondroitin sul­fate A, Band C from consideration as the main67Ga.binding acid mucopolysaccharide, based uponresults from heparitinase, heparinase, and chon­droitinase ABC treatment.

67Ga can be a trivalent cation in solution, andnaturally this cation can bind strongly to a cation­N.M.e. 12/5--e

exchange resin?" and heparin'" in solution, although67Ga is present as negatively charged complexes undercertain circumstances. Acid mucopolysaccharide is asoluble cation-exchange resin-like substance, and thesulfonic groups in the structure bind strongly topositively charged gallium complexes. Among acidmucopolysaccharides, keratan polysulfate binds posi­tively charged complexes more strongly than anyother acid mucopolysaccharide, because it is an over-

362 Arsusm ANOO and Irsoxo ANOO

sulfated acid mucopolysaccharide. As shown inTable 2, keratan polysulfate which is contained in theliver, is also confirmed by separation with anion­exchange resin. Among the acid mucopoly­saccharides in liver, the amount of keratan poly­sulfate is small, but it is presumed that keratanpolysulfate plays an important role in liver accumu­lation of 67Ga, because of its strongly negative charge.We have shown that the principal 67Ga-binding acidmucopolysaccharides in tumor, liver, spleen, lung,kidney, heart and abscess are very similar"~) Wethink that keratan polysulfate plays the most im­portant role concerning 670a accumulation in thesesoft tissues.

Acknowledgements-We wish to thank Drs K. Sakurai andK. Horie for their comments and suggestions and the MissesJ. Takebayashi and K. Yokohama for experimental assis­tance . This work was supported in part by a Grant-in-Aidfor Scientific Research and a Grant-in-Aid for CancerResearch from The Ministry of Education, Science andCulture.

References1. Ando A. et al. Radioisotopes 13, 161 (1974).2. Ando A. et al. Radioisotopes 26, 421 (1977).3. Ando A. Studies on the Tumor Affinity of 169rb, 167Tm,

"Go and IlIln. PhD Thesis pp. 82-99 (Kyushu Univer­sity, Japan. 1979). (In Japanese).

4. Ando A. tt 01. Radioisotopes 29, 250 (1980).5. Ando A. et al. Proc. 3rd World Congress of Nuclear

Medicine and Biology /l pp. 1772-1775, Paris (1982).6. Ando A. et at. Int. J. Nucl. Med. BioI. 10, 1 (1983).7. Ando A. et at. Eur. J. Nucl. Med. 7, 298 (1982).8. Ando A. et aI. Eur. J. Nucl. Med. 8, 440 (1983).9. Kojima S. tl aI. Jap, J. Nucl. Med. 19,67 (1982).

10. Sasaki T. tt al. Eur. J. Nucl. Med. 7, S45 (1982).II. Kojima S. et al. Eur. J. Nucl. Med. 8, 52 (1983).12. Hama Y. et al. Eur. J . Nucl. Med. 9, 51 (1984).13. Ando A. and Ando I. Abstracts ofTth Japanese Carho-

hydrate Symposium. pp. 96-97, Osaka (1984).14. Lowry O. H. et 01. J . BioI. Chem. 193,265 (1951).15. Brown A. H. Arch. Bioehem. 11,269 (1946).16. Aminoff D. Biochem. J. 81, 384 (1961).17. Trevelyan W. E. and Harrison J. S. Biochem. J. SO, 298

(1952).18. Schiller A. et aI. J. BioJ. Chem. 236, 983 (1961).19. Mathews M. B. and CifoneUi J. A. J. BioI. Chem. 240,

4140 (1965).20. Ando A. et al. Eur. J. Nucl. Med. 9, 300 (1984).21. Ando A. et al. Radioisotopes 13, 52 (1974).