CLINICALSCIENCES

DIAGNOS11C NUCLEAR MEDICINE

SalivaryGlandAccumulationofMeta-[13'l]lodobenzylguanidine

M.Nakajo,B.Shapiro,J.C. Sisson,D.P.Swanson,andW.H.Beierwaltes

Universityof Michigan,AnnArbor,Michigan

intenseuptakeof m-[1311]iodobenzylguanidine(1-131MIBG) hasbeen observed in the salivaryglandsof patientsundergoingscintigraphyfor the locationof sus pectedpheochromocytomas.Thisuptakeof radioactivitywas notdueto free 1-131 derived from the 1-131MIBG but rather to uptake of 1-131MIBG by sympathetic neuronalelementsinthe salivaryglands.Inkeepingwith this,administrationoftn cyclic antidepnessantsreversiblyblockedsalivaryuptake of 1-131MIBG.Further more, 1-131 MIBG uptake was markedly diminishedby the ipsilaterai salivary glandsin a patientwith Homer'ssyndrome,andwas bilaterallydiminishedina pa tient withsevereidiopathicsympatheticautonomicneuropathy.The salivarygland uptake of 1-131MIBGmay providea meansfor the studyof sympatheticinnerva tion of these organs,and thusfor the studyof generalizeddisordersof autonomic innervation.

J NucI Med 25: 2—6,1984

Meta- [I- 131]iodobenzylguanidine (I- I31 MIBG) is excretion mechanism of 1-131 MIBG accumulation in a radiolabeled analog of the adrenergic blocking agent the salivary glands. guanethidine (1). Its affinity for the adrenal medulla has made it useful in the detection of pheochromocytomas MATERIALS AND METHODS and adrenal medullary hyperplasia (2,3). In the canine Because the salivary glands are known to concentrate adrenal medulla 1-131 MIBG is sequestered mainly in I-I 31 ions, it was first necessary to exclude the possibility the chromaffin storage granules (4). In addition it ap that the observed salivary images were merely due to the pears that a major component of MIBG retained in uptake of free radioiodide present in the radiopharma myocardium is that sequestered within the norepi ceutical or liberated from it in vivo. To do so, the fol nephrine storage vesicles of the adrenergic nerves of the lowing experiments were performed. canine heart (5). 1-131 MIBG is thus believed to share Studies in man. I. As the salivary glands, thyroid, and uptake and storage mechanisms similar to those of nor stomach are all known to concentrate iodide (9) the epinephrine. frequency of visualization of these organs was evaluated We have frequently observed prominent visualization in the images of I51 patients referred for the location of of the salivary glands on the 1-131 MIBG head-chest possible pheochromocytomas (67 male; 84 female, ages images routinely obtained to detect extraadrenal and 6—73yr). metastatic pheochromocytomas (6). Accumulation of 2. Theinfluenceof thedoseof iodideadministered 1-131 MIBG in the salivary gland may be related to was noted on the frequency of visualization of salivary sympathetic innervation as this organ which, like the glands, thyroid, and stomach. Seventy-five patients had heart, is richly supplied by sympathetic nerves (7,8). received three drops of saturated solution of potassium This study was undertaken to elucidate the uptake and iodide per day (SSKI, I20 mg of iodide), 61had received Received Jan. 31, 1983; revision accepted July 21, 1983. Lugol's solution six drops per day (40 mg of iodide) to For reprints contact: Dr. B.Shapiro, Div.of Nuci. Med., University block thyroidal uptake of I- I31. Administration of io of Michigan Hospitals, Ann Arbor, MI 48109. dides was begun on the day before tracer injection and

2 THE JOURNAL OF NUCLEAR MEDICINE CLINICAL SCIENCES DIAGNOSTIC NUCLEAR MEDICINE continued for at least 4 days afterwards. The remaining Salivary gland concentration. The subjects were nine 15 patientsreceivednoiodides,eitherinadvertentlyor patients with no evidence of salivary gland disorders who because of previous thyroidectomy. The images were were referred for I- 131 MIBG imaging (three male, six obtained at 4 hr in some cases and at 24 and/or 48 hr female, ages 26—66yr). All subjects received SSKI as after the intravenous injection 0.5 mCi of I- I31 MIBG described above. After obtaining informed consent, blood per I .7 m2 (2). Visualization of the salivary glands samples and unstimulated mixed saliva were collected (parotid) and thyroid were evaluated on the posterior at 15 mm, and at 1, 4, 24, and 48 hr following the injec head/chest images. In selected cases, additional anterior tion of the diagnostic dose of I- 131 M IBG. Plasma and and lateral images of the head and neck were obtained saliva samples were counted in an auto-gamma counter, for detailed delineation of all the salivary glands. The with corrections for radioactive decay, background, and region of the stomach was examined on anterior and counter efficiency. Saliva-to-plasma I- I31 ratios were posterior abdominal images. calculated. Studies in the dog. As the dog parotid gland is able to Chemical forms of the radioactivity in saliva. The concentrate iodides and the submandibular gland is not subject was a 61-yr-old white man with metastatic (10,1 1), this animal provides an opportunity to deter pheochromocytoma, who was referred for I-I31 MIBG mine whether salivary gland activity is due to the uptake therapy to his malignant lesions (12). The unstimulated of free 1-131 ions by acinar tissue or 1-131 MIBG by mixed saliva was collected I hr after completion of an i.v. neuronal elements. To do this, tissue distribution studies infusion (over 90 mm) of 100 mCi I-I 31 MIBG. After were performed on three female mongrel dogs (2 1—27 collection of the unstimulated saliva, a collection was also kg) that were injected with 200 @Ciof I- 131 MIBG in made following stimulation of the salivary glands by travenously. No iodides were administered and animals sugarless chewing gum. The chemical form of the ra were killed by intravenous sodium pentobarbital 2 hr dioactivity in the both unstimulated and stimulated sa after tracer injection. Duplicate tissue samples of sub liva was determined using thin-layer chromatography mandibular and parotid gland were weighed and counted (silica gel G support, acetate/ethanol ( 1:I) Rf I- 131 in an auto-gamma counter, with corrections for radio MIBG = 0. 1, Rf I- 13 1 iodide = 0.6) following the dilu active decay, background, and counter efficiency. The tion of the saliva samples. tissue concentration was expressed as % kg dose/g. RESULTS To further elucidate the mechanism of 1-131 MIBG uptake, a detailed retrospective examination was made Table 1 shows the frequency of visualization of the of the group of patients (seven) in whom the salivary salivary glands, thyroid, and stomach observed on 1-131 glands were not visualized. This included four patients MIBG scintigrams. The salivary glands are visualized taking tricyclic medications, one with in 92% to 100%of patients, whereas gastric uptake was profound sympathetic autonomic neuropathy, and one never observed despite the fact that both organs share case of unilateral decreased I-i 31 MIBG uptake in the similar mechanisms for the uptake of iodide. The thyroid ipsilateral salivary glands of a woman with Homer's gland was seen in all instances where iodide treatment syndrome. was omitted, and in no more than 7% where iodides were Additional studies were performed to determine administered. The presence or absence of pheochromo whether the radioactivity visualized in the salivary glands cytoma did not appear to affect visualization of any of at scintigraphy was excreted in the saliva and, if so, in these organs. Figure 1 shows the salivary glands in the what chemical form. presence of SSKI administration.

TABLE1. VISUALIZATIONRATE(PERCENT)OF ThE SALIVARYGLANDS,ThYROIDS,AND STOMACH on 1-131MIBGIMAGES Thyroid blocking agents (dose/day) solutionsS Lugol's (120mgof I)(40 mgof I)Omitted Organs 4 hrKI hr24hr48 hr4 hr24 hr 48 hr 4 hr 24 hr 48

Salivarygland 100 100 92 — 100 100 — 100 92

Thyroid 0 0 1 — 3 7 — 100' 100' Stomach 0 0 0 0 0 0 0 0 0 Numberof patients 1(1)t 34(5) 76(9) 5(2) 36(12) 44(15) 1 9 13(1)

4 Percent in the patients with thyroids (n 3 at 24 hr. 4 at 48 hr). t ( ) = number harboring pheochromocytomas.

Volume 25, Number I 3 NAKAJO. SHAPIRO, SISSON. SWANSON, BEIERWALTES

gland images were obtained (Fig. 2). There was in ad dition a fourth patient who had taken hydro chloride 600 mg/day up to the time of I- 131 MIBG in @@-•t jection. This drug is a with action r. similar to hydrochloride; it had a similar effect on the salivary glands, reducing visualization to a bare minimum. One patient had evidence for severe autonomic neu ropathy. His plasma concentrations were @ F.'.- extremely unusual in that on several occasions they demonstrated very low recumbent (NE) associated with normal epinephrine (E): NE 39, 24, and 15 pg/mI; E 80, 86, 50 pg/mI. There was no significant increase in norepinephrine on standing. These values suggested a severe adrenergic autonomic neuropathy. FIG. 1. Posterior head-chest image of patient taking SSKI,at 24 Figure 3 shows the posterior head-chest image of this hr after -131 MIBG.Salivaryglandsshowclearly,butnotthyroid. patient, in whom no radioactivity was seen in any salivary gland. The tissue distribution studies in dogs showed that the In the remaining three patients, the causes of non concentrations in the submandibular glands (which do visualization of the salivary glands could not be identi not concentrate iodide) were 0.502% kg dose/g ±0.059 fled. The salivary glands were seen faintly on the 24-hr (mean :1:s.c.m., n six glands) while those in the parotid images that were available in two of them. glands (which do concentrate iodide) were 0.475 ±0.124 Examination of the salivary gland intensity between (n six glands). 24-hr and 48-hr images was possible in 64 patients. The Thus it appears that the activity observed in the sali intensity appeared to decrease between 24 hr and 48 hr vary glands is not due to the concentration of free io in 53% of the cases, with no change in the rest. dide. The final case was that of a 72-yr-old white woman Seven patients showed no salivary gland visualization with a Homer's syndrome on the right side. She had at 48 hr after tracer injection. Of these, four were re episodes of headache, palpitations, and hypertension. She ceiving tricyclic antidepressant therapy. Three of these gave a history of thyroidectomy for goiter at age 40, with took imipramine hydrochloride, a tricyclic antidepres inadvertent sympathectomy leading to a complete sant known to inhibit the neuronal uptake of norepi right-sided Homer's syndrome. She was referred for nephrine and guanethidine (13). Two patients were I- I3 1 MIBG imaging because of a suspicion of pheo taking the drug at a dose of 75 mg/day at the time of I- chromocytoma. Anterior and lateral head images with 131 MIBG injection, while the third had been taking 40 I-I 31 MIBG were added to the routine images. After mg/day until 7 days before 1-131 MIBG injection. In obtaining the informed consent, salivary gland imaging two of the patients 1-131 MIBG scintigraphy was re peated at 3 and 3½wk following withdrawal of im ipramine hydrochloride, and this time clear salivary

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A B FIG.2. (A)Salivaryglandsareseenon48-hrposteriorhead-chest FIG.3. Posteriorhead-chestimageat 24 hr after 1-131MIBO,from 1-131MIBOimage, 3 wk after discontinuation of imipramine hy patient with idiopathic autonomic neuropathy.No radioactivity ap drochloride administration. (B) They had failed to show on 48-hr pears in salivaryglands;thyroidaccumulationis due to inadvertent posterior head-chest1-131MIBGimagetakenduringadministration omission of iodide administration. Four radioactive surface markers of drug(75 mg/day). are onshouldertipsandaxillae.

4 THE JOURNAL OF NUCLEAR MEDICINE CLINICAL SCIENCES DIAGNOSTIC NUCLEAR MEDICINE

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FIG. 4. Anteriorimagesof patientwith right-sided Homer's syndrome. Discrep ancyinrightsalivaryglandvisualizationis obviousbetween24-hr 1-131MIBG(A)and 20-mm 99@'TcO4 (B) images.

was performed 20 mm after intravenous injection of 5 not simple concentration of radioiodide. Although the mCi of Na 99m1c04, and the two sides were compared. dosage of iodide (40-130 mg/day) was sufficient to The concentration mechanism for pertechnetate in the block iodide uptake by the thyroid, such doses may not salivary glands is similar to that of iodide (14—16),and fully inhibit uptake by the salivary glands and stomach thus this experiment permitted the examination of the (16—19).However, only the salivary glands were visu uptake of 1-131 MIBG in neuronal elements and Tc-99m alized, and never the stomach despite the fact that both by glandular acini. organs can concentrate I-131 ions (or 99mTcO4—)by the Figure 4 contrasts the findings in the salivary glands same mechanism and with similar affinity (9,20). between I- I31 MIBG (A) and 99mTcO4—(B) imaging This discrepancy between salivary gland and gastric in this patient with right-sided Homer's syndrome. The visualization precludes a simple concentration of I- I31 difference in the salivary gland images is striking in the ion, and suggests a specific uptake of 1-131 MIBG. The two studies. The right-sided glands are not seen with tissue studies in dogs likewise show that I- 131 MIBG is MIBG, whereas they are a bit darker, ifanything, with equally concentrated in the submandibular and parotid pertechnetate, especially the parotid. glands, both being sympathetically innervated (/0,11), Excretion mechanisms. Table 2 shows radioactivity although only the parotid is able to concentrate io from I- I31 MIBG in plasma and saliva, and the saliva dide. to-plasma ratio with time. The mean radioactivity was The neuronal nature of the 1-131 MIBG uptake is highest at 15 mm, then declined in both plasma and sa further suggested by: liva. The saliva-to-plasma ratio was greater than 1.0 at I. The inhibition of such uptake by tricyclic antide all times. The greatest mean ratio was observed at 4 hr. pressants. 1-131 MIBG is a derivative of guanethidine, Chemical forms of the radioactivity were 98% free I-I 31 and shows structural similarities to norepinephrine (1,2). and 2% 1-131 MIBG in the unstimulated saliva, and 93% High concentrations of radioactivity from C-14 guan and 7%, respectively, in the saliva stimulated with ethidine have been found in the salivary glands of mice chewing gum. The activity excreted in the saliva repre on whole-body autoradiography (21 ). Antagonism of sented only a minute fraction of that in the salivary guanethidine by tricyclic has been well gland. documented (22—24).It inhibits the norepinephrine uptake mechanism in the peripheral adrenergic neuron DISCUSSION in man and thereby prevents uptake of guanethidine at The data summarized in Table I show that the its site ofaction (13). mechanism of salivary gland uptake of 1-131 MIBG is 2. Thelackof 1-131 MIBG uptakeby thesalivary

TABLE2. RADiOACTIVITY(1O@X cpm/l,mean±s.e.m.)FROM1-131MIBGINPLASMAANDSALIVA,AND SALIVA-TO-PLASMARATIO injection15mm Time after 1-131MIBG 1 hr 4hr 24hr 48hr Plasma 11.9± 1.3(9)' 6.5±0.8(9) 4.4±0.6(9) 2.5±0.5(7) 1.8 ±0.3(8) Saliva 72.4 ±10.5(9) 55.2 ±7.0(9) 53.3 ±8.2(9) 20.8 ±2.7(9) 10.8 ±2.9(8) Saliva/Plasma ratio 6.9± 1.3(9) 9.6±1.6(9) 13.1 ±2.1(9) 10.8 ±2.7(7) 5.9±1.6(8)

. ( ) = No. of patients.

Volume 25, Number I 5 NAKAJO. SHAPIRO, SISSON, SWANSON, BEIERWALTES glands of a patient suffering from severe autonomic analog. J Nuci Med 22:22-3 1, I981 neuropathy. 6. NAKAJOM, SHAPIROB,Co@@J,etal: Thenormaland 3. The ipsilateral decrease in I- 13 1 MIBG uptake by abnormal distribution of the adrenomedullary imagingagent ‘31l-metaiodobenzylguanidine (‘311-MIBG)in man: Evalu the salivary glands of a patient with specific adrenergic ation by scintigraphy. J. Nucl Med 24:672-682, 1983 sympathetic denervation of these glands due to surgically 7. WHITBY LG, AXELRODJ, WEIL-MALHERBEH: The fate induced Homer's syndrome. of H3-norepinephrine in animals. J Pharmacol Exp Ther Although the secretion of saliva is primarily governed 132:193—201,1961 by parasympathetic innervation of the salivary glands, 8. IVERSEN LL, GLOWINSKI J, AXELROD J: The physiolog ical disposition and metabolism of norepinephrine in immu these organs receive a rich sympathetic innervation and nosympatbectomized animals. J Pharmaco! Exp Ther 151: are sites of norepinephrine uptake (25). The sympathetic 273—284,1966 nervous system serves to modulate the composition of 9. MYANTNB,CORBETTBD,HONOURAJ,etal: Distribu saliva secreted (26). The clearance of I-131 MIBG from tion of radioiodine in man. Clin Sd 9:405—419,1950 the plasma was very rapid and the saliva-to-plasma ratio 10. BURGEN ASV, SEEMAN P: The secretion of iodide in saliva. Can J Biochem Physiol 35:481-489, 1957 of radioactivity was always greater than 1.0 from 15 mm 11. COHEN B, MYANT NB: Concentration of salivary iodide: to 48 hr after 1-131 MIBG injection. The majority of A comparative study. J Physiol 145:595—610,1959 radioactivity in the saliva was in the form of free I-i 31 12. SISs0N JC, SHAPIRO B, BEIERWALTES WH, et al: ion. Stimulation by chewing caused a slight increase in Treatment of malignant pheochromocytomas with a new ra I- 13 1 MIBG in the saliva. This excretion of radioactivity diopharmaceutical. C/in Res 31:547A, 1983 (abst) 13. MICHELL JR, CAVANAUGH JH, ARIAS L, et al: Guan represents only a small fraction of that in the gland. ethidine and related agents. III. Antagonism by drugs which The source of both the free I- 131and I- 131 MIBG is inhibit the norepinephrine pump in man. J Clin Invest 49: probably the sympathetic neurons of the salivary glands, 1596-1604,1970 although some direct concentration of the radiophar 14. ALEXANDER WD, HORDEN RM, MASON DK, et al: maceutical by acinar cells may occur. However, the Comparison ofthe concentrating ability of the human salivary glands for bromine, iodine and technetium. Archs Oral Biol 1-131 MIBG seen in images of the salivary glands ap 11:1205—1207,1966 pears to be principally the neuronal component. 15. HARDEN RMCG, HILDITCH TE, KENNEDY I, Ct al: Up Salivary gland imaging with radioiodinated MIBG take and scanning of the salivary glands in man using per may be useful in assessing disorders of the gland's sym [email protected]/in Sci 32:49—55,1967 pathetic innervation, and thus may be a “diagnostic 16. HARDEN RMcG, ALEXANDER WD, SHIMMINS J, et al: Quantitative aspects of the inhibitory effect ofthe iodide ion mirror―of a generalized adrenergic neuropathy such as on parotid salivary iodide and pertechnetate secretion in man. that of diabetes. J Lab ClinMed 71:92-100,1968 17. FERGUSON MH, NAIMARK A, HILDES JA: The interre ACKNOWLEDGMENTS lationshipbetweenthe parotidsecretionofthiocyanate, iodide, andchloride.Can J BiochemPhysiol35:333—337,1957 We thank Dr. T. Mangner and Holly Anderson-Davis for the 18. BROWN-GRANT K: Extrathyroidal iodide concentrating manufacture of I- 131 MIBG the Phoenix Memorial Laboratory for mechanisms. Phys Rev 41:189—213, 1961 the use of their radiochemistry facilities, and Ms. Joanne Boldt for 19. TAPLIN GV, JOHNSON DE, DORE EK, et al: Suspensions preparation of the manuscript. ofradioalbumin aggregates for photoscanning the liver, spleen, This work was supported by the followinggrants: DHEW #3M01 lung and other organs. J Nuci Med 5:259-275, 1964 RR00042-22 Sl CLR, NIH #R01 AM 21477, NIAMDD #5P60 20. HARDEN RM, ALEXANDER WD, SHIMMINS J, et al: AM 20575, NCI #09015, and the Nuclear MedicineResearchFund. Quantitative uptake measurements of @“Tcin salivary glands B.S. is the recipientof an NIH Clinical AssociatePhysicianAward (DHEW #3M01 RR00042-22S1CLR) and stomach and concentration of 99mTc,132!and 82Brin gastric juice and saliva. Strahientherapie Sonderbande 67: 77—87,1968 REFERENCES 21. FURST CJ: Studies on the distribution and excretion of a I. WIELAND DM, WU i-I, BROWN LE, et al: Radiolabeled metabolite of guanethidine in the rat. Br J Pharmacol Che adrenergic neuron-blocking agents: Adrenomedullary imaging mother32:57-64,1968 with [‘31lliodobenzylguanidine. J Nuci Med 21:349—353, 22. LEISHMANAWD, MATTHEWSHL, SMITHAJ: Antago 1980 nism of guanethidine by imipramine. Lancet 1:112, 1963 2. SISS0NJC, FRAGERMS, VALKTW, et al: Scintigraphic 23. MICHELL JR. ARIAS L, OATES JA: Antagonism of the localization of pheochromocytoma. N EnglJ Med 305:12-17, antihypertensive action ofguanethidine sulfate by I981 hydrochloride. JAMA 202:973-976, 1967 3. VALK TW, FRAGER MS. GROSS MD, et al: Spectrum of 24. MEYER JF, MCALLISTER CK, GOLDBERG LI: Insidious pheochromocytoma in multiple endocrine neoplasia. A scm and prolongedantagonism ofguanethidine by . tigraphic portrayal using ‘311-metaiodobenzylguanidine.Ann JAMA 213:1487-1488,1970 Intern Med 94:762—767,1981 25. LEE C-M, JAVITCH JA, SNYDER SH: Recognition sites for 4. W'IELANDDM,BROWNLE,TOBESMC,etal: Imagingthe norepinephrine uptake: Regulation by neurotransmitter. primate adrenal medulla with [1231]and [‘@‘I]metaiodo Science 220:626-629, 1983 benzylguanidine: Concise communication. J Nuci Med 22: 26. ABE K, YONEDA K, FUJITA R, et al: The effects of epi 358—364,1981 nephrine, norepinephrine and on the types of 5. WIELAND DM, BROWN LE, ROGERS WL, et al: Myocar proteins secreted by rat salivary glands. J Dent Res 59: dial imaging with a radioiodinated norepinephrine storage 1627-1634,1980

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