67Ga Accumulation Research Articles

Subcellular distribution of gallium-67 in tumor and liver

Subcellular distribution of 67Ga was quantitatively determined to evaluate the role of the lysosome in accumulation of 67Ga in malignant tumor tissue and the liver using three different tumor models and the host liver. In Yoshida sarcoma and Ehrlich tumor, most of the radioactivity of 67Ga was localized in the supernatant fraction, and only a small amount of radioactivity was localized in the mitochondrial fraction, which contains lysosomes. In the liver, however, most of the radioactivity was concentrated in the mitochondrial fraction. The radioactivity of this fraction increased with time after the administration of 67Ga and reached approximately 50% of total radioactivity within 24 h. In the case of hepatoma AH 109A, radioactivity of the mitochondrial fraction increased with time after administration, and about 30%, of total radioactivity was concentrated in this fraction after 24 h. It is concluded that lysosome does not play a major role in the tumor concentration of 67Ga, although it may play an important role in the liver concentration of 67Ga. In the case of hepatoma AH109A, it is presumed that lysosome plays a considerably important role in the tumor concentration of 67Ga, hepatoma AH 109A possessing some residual features of the liver.

Uptake of 67Ga in the heart of rats treated with isoproterenol.

Gallium-67 citrate (67Ga) accumulation and various enzyme activities during the repair of rat heart with infarct-like lesions induced by isoproterenol (ISP) treatment were measured for 10 days after treatment. Serum creatine phosphokinase (CPK) and glutamic oxalacetic transaminase (GOT) activities were increased immediately after ISP treatment, reaching maximum levels of activity of 545 +/- 64 U/ml and 542 +/- 94 KU/ml, respectively, within 12 h. Uptake of 67Ga in the rat heart was elevated 12 h after ISP treatment, reaching a maximum on day 1 (0.473 +/- 0.015% dose/g heart). This pattern was essentially similar to the pattern of uronic acid content in the 1.2 M NaCl fraction, which contained mainly heparan sulfate (HS). The activity of glucose-6-phosphate dehydrogenase (G-6-PDH), a marker enzyme for fibrogenesis of damaged tissues, was also elevated 12 h after the ISP treatment, reaching a maximum of approximately 2.47 times that of the control heart on day 1. On the other hand, there were no significant changes in the 67Ga uptake and uronic acid content in any of the fractions of the liver and kidneys. These findings suggested that HS might be an acceptor for 67Ga accumulation during the repair of rat heart with infarct-like lesions, in accord with our previous results on CCl4-damaged rat liver.

In Vivo Distribution of Carrier Protein/67Ga-Complexes

The uptake of 67Ga as citrate, chloride and complexed by carrier-proteins (lactoferrin and transferrin) has been studied in tumor- and inflammatory lesion-bearing rats. Different uptake patterns are shown by tumors and lesions. 67Ga-transferrin complexes are taken up to the highest extent by tumors and inflammatory lesions. The comparative distribution studies using normal animals indicate a systemic increase of 67Ga uptake by tumor- and lesion-bearing animals which might be of importance in explaining the mechanism of 67Ga accumulation. The role of ionic environment changes and radioactivity concentration by isomorphous ionic replacement is discussed.

Leukocyte and 67Ga-citrate dynamics in experimental subcutaneous Streptococcus faecalis infections.

The dynamics of white blood cell (WBC) and 67Ga-citrate accumulation were studied in rabbits with subcutaneous polyethylene chambers. Uninfected chamber fluid (CF) contained less than 1,000 WBCs/mm3, most of which were mononuclear. After 67Ga injection, radioactivity increased slowly in uninfected fluid, peaked between 24 and 48 hours, and then gradually decreased. 67Ga scans showed no uptake in excess of background levels around the uninfected chambers. After injection of Streptococcus faecalis directly into the chambers, bacterial concentrations initially decreased, increased by 4-24 hours, and then decreased slightly. WBCs began to increase 4 hours after infection due to influx of polymorphonuclear leukocytes. 67Ga localized in infected chambers before the increase in WBCs. Use of the subcutaneous chamber model could help elucidate the mechanism(s) of 67Ga accumulation at sites of inflammation.

67Ga scintigraphy as an index of disease activity in pulmonary sarcoidosis.

Gallium-67 scintigraphy was performed in 38 patients with pulmonary sarcoidosis to assess its value as a supplement to the clinical, radiographical and functional investigations. In 32 (84%) of the 38 patients the scan was abnormal and showed 67Ga uptake in the pulmonary parenchyma and/or hilum. The incidence and severity of pulmonary symptoms correlated poorly with the localization and degree of 67Ga accumulation. During the clinical follow-up of untreated patients 67Ga scintigraphy showed regression earlier than chest radiography. Large doses of corticosteroids decreased the accumulation of 67Ga in the pulmonary parenchyma and hilum. The chest radiographical improvement was more gradual. The 67Ga scan can be used as an index of disease activity in the follow-up of patients with pulmonary sarcoidosis, whether or not they are treated with corticosteroids. Nevertheless, the results have to be considered together with other clinical data.

The mechanism of 67Ga uptake in animal and human tumours.

The subcellular distribution of 67Ga has been studied by differential centrifugation in 3 transplantable mouse tumours, 3 transplantable rat tumours, 1 dog tumour, 3 human tumour xenografts and 2 human tumours in situ at various times after injection of the citrate complex. From 24 h post injection of nuclide was located predominantly in lysosomal structures in all the tumours studied. Studies in two murine tumours showed marked differences in the rate of lysosomal accumulation of 67Ga. In the ADJ/PC6 plasmacytoma lysosomal uptake of 67Ga had reached a plateau within 15 min while in the S180 tumour lysosomal accumulation of the nuclide occurred over the first 24 h. Normal mouse liver showed a similar pattern to this latter tumour. It is postulated that these variations in the rate of lysosomal accumulation of 67Ga reflect differences in the permeability of the lysosomal membrane. While large amounts of 67Ga were found in the crude nuclear fraction of some tumours this was attributed to unbroken cells as studies with purified nuclei from 7 different tumours indicated that between 2 and 14% of the total tumour 67Ga was associated with the nuclei.

Subtraction scintigraphy with 67Ga-citrate and 99mTc-colloid in the diagnosis of intrahepatic masses.

Subtraction scintigraphy of the liver with 67Ga-citrate and 99mTc-colloid (99mTc-phytate) was performed by subtracting the image of the latter from the image of the former in 34 patients who were suspected of having intrahepatic masses, especially hepatoma. The computer used was Scintipac 1200 (32 KW memories and 2.4MBX2 disk memories). Both images were taken in a digital form (128 X 128 elements). After normalizing both images, 4 different factors (0.6, 0.8, 1.0, and 1.2) were applied to the 99mTc image before the subtraction from the 67Ga image. We found that this technique was very useful for the detection of abnormal 67Ga accumulation in the liver.

The mechanism of the localization of 67gallium citrate in experimental abscesses.

67Ga accumulation in turpentine-induced abscesses, from 5 h to 20 days old, in the rat has been investigated, and the results indicate that this is dependent on polymorphonuclear leukocyte (PMN) infiltration of the inflamed site. 67Ga concentration 24 h after injection correlates well with the activities of the lysosomal enzymes, aryl sulphatase and beta-glucuronidase, P less than 0.001, and with the DNA content of the tissue. There is no direct relationship with the rate of DNA synthesis. The mechanism of lysosomal incorporation into PMNs is consistent with the factors involved in 67Ga uptake into tumours and normal tissues.

67Ga Scanning in the Evaluation of Esophageal Carcinoma

Eighty-nine patients with histologically proved esophageal carcinoma were scanned with 67Ga to screen for extramural tumor extension and lymph-node involvement. Radiation dose and reduction of uptake were correlated. 67Ga accumulation indicated extramural extension with a sensitivity of 67% and a specificity of 93%. Marked uptake in an extraprimary site in the mediastinum or upper abdomen indicated lymph-node involvement with a sensitivity of 27% and a specificity of 100%. Irradiation with more than 20 Gy (2,000 rad) reduced uptake (P less than 0.05). 67Ga scanning appears to be useful in the evaluation of esophageal carcinoma.

Studies of Gallium Accumulation in Inflammatory Lesions

The kinetics of 67Ga accumulation in experimental inflammatory exudates were studied. In six rabbits with S. aureus induced abscesses, serial samples of exudate and blood were obtained at 1, 2, 4, 24 and 48 hrs after intravenous injection of 67Ga. The accumulation of 67Ga in the inflammatory exudate was slow with an accumulation half-time of 5.5 hrs. The concentration of 67Ga in the abscesses approached that of blood 48 hrs after injection. Analysis of the distribution of 67Ga in the inflammatory exudate revealed that the portion of 67Ga in the cellular fraction (1,600 xg pellet) correlated best with the number of non-viable polymorphonuclear leukocytes (PMN) (r = 0.81). Its correlation with total number of PMN and bacteria was r = 0.69 and r = 0.35, respectively. Autoradiographic studies confirmed that the majority of 67Ga in the cellular fraction of the exudate was associated with non-viable PMN's.

Distribution of 67Ga-citrate in Tumor Tissues and Various Organs—Macroautoradiographic and Scintigraphic Studies—

Localization of 67Ga in various tissues was demonstrated by whole-body autoradiography of tumor-bearing mice in order to obtain comprehensive information which would aid in making more accurate interpretations of clinical scintigrams. The macroautoradiograms (ARG's) showed the most intense accumulation of 67Ga in the reticuloendothelial tissues, the wall of the intestinal tract and tumor tissues. 67Ga nonspecifically accumulated in the abdominal region and was apparently excreted mostly from the kidneys and from the mucosa of the intestinal tract. In the reticuloendothelial system such as bone marrow, liver and lymph nodes were sometimes difficult to distinguish from the lung tumor. In the 67Ga-scintigram the high uptake of 67Ga was seen in these organs. Tumor in the lung could be readily detected as the alveolar structure is occupied with a considerable amount of air and has much lower activity per unit volume in the normal lung tissue. Thus the application of 67Ga in autoradiography in experimental animals provided useful information which should assist in analyzation of routine 67Ga-scintigrams in patients with neoplastic diseases.

Augmented skeletal accumulation of Ga-67: A variant in children

Augmented skeletal accumulation of Ga-67: A variant in children

Bony Lesions in Systemic Mastocytosis

Bone, bone marrow and gallium citrate Ga 67 scans were performed on a patient with systemic mastocytosis and bony involvement to evaluate their diagnostic value in such patients. The bone scan revealed increased tracer concentration in the involved areas. These abnormalities were less prominent than those on the roentgenograms, suggesting that only a part of the roentgenographic abnormalities were associated with reactive bone formation. Bone scanning may be less sensitive than roentgenograms to detect the full extent of the bony lesions of systemic mastocytosis. The bone marrow scan revealed a normal central marrow with peripheral marrow expansion. Possibly, the central marrow infiltration by mast cells was sufficient to interfere with its hemopoietic function to a degree that made it necessary to reactivate peripheral marrow tissue. There was no significant 67Ga accumulation in the bony lesions of systemic mastocytosis.

67Ga lung scan. An aid in the differential diagnosis of pulmonary embolism and pneumonitis.

Twenty-three patients patients with clinical signs of pulmonary embolic disease and lung infiltrates were studied to determine the value of gallium citrate Ga 67 lung scan in differentiating embolic from inflammatory lung disease. In 11 patients without angiographically proved embolism, only seven had corresponding ventilation-perfusion defects compatible with inflammatory disease. In seven of these 11 patients, the gallium 67 concentration indicated inflammatory disease. In the 12 patients with angiographically proved embolic disease, six had corresponding ventilation-perfusion defects compatible with inflammatory disease. None had an accumulation of 67Ga in the area of pulmonary infiltrate. Thus, ventilation-perfusion lung scans are of limited value when lung infiltrates are present. In contrast, the accumulation of 67Ga in the lung indicates an inflammatory process. Gallium imaging can help select those patients with lung infiltrates who need angiography.

Study of Subcellular Distribution of 67Ga in Tumor and Liver

Subcellular distribution of 67Ga was quantitatively determined to evaluate the role of lysosome in accumulation of 67Ga in malignant tumor tissue and liver. The following animals and transplanted tumors were used: rats implanted with Yoshida sarcoma and hepatoma AH109A; mice implanted with Ehrlich tumor. 67Ga-citrate were injected to the rats intravenously and to the mice intraperitoneally. Ten minutes to 48 hours after the administration of 67Ga-citrate, the animal were sacrificed, and the tumor tissues and liver were excised. Subcellular fractionation of tumor tissues and livers were carried out according to the method of Hogeboom and Schneider. Radioactivity of each fraction was counted by a well type scintillation counter, and protein of each fraction was measured according to Lowry's method. In Yoshida sarcoma and Ehrlich tumor, most of the radioactivity was localized in the supernatant fraction, and small amount of radioactivity was localized in the mitochodrial fraction (lysosome contains in this fraction). But in the liver, most of the radioactivity was concentrated in the mitochondrial fraction and the radioactivity of this fraction was increased with the passage of time after administration. Twenty-four hours later, about 50% of total radioactivity was accumulated in this fraction. In the case of hepatoma AH109A, radioactivity of mitochondrial fraction was increased with the passage of time after administration, and about 30% of total activity was concentrated in this fraction at 24 hours after administration. From these results it is concluded that lysosome doses not play an important role in the tumor concentration of 67Ga and lysosome plays an important role in the liver concentration of 67Ga. In the case of hepatoma AH109A it is presumed that lysosome plays considerably important role in the tumor concentration of 67Ga, hepatoma AH109A having some nature of liver.

On the mechanism of accumulation of 67Ga by tumors.

There is strong experimental evidence indicating that a competitive binding of 67Ga3+ to Ca2+- and Mg2+-binding sites rather than a metabolic process is involved in the accumulation of this radioisotope. These observations suggest that in tumors, as well as in other inflammatory and infectious processes, the most important role in 67Ga accumulation is played by a higher availability of those binding sites than in normal tissue.

Gallium Citrate Ga 67 Accumulation In Pseudomembranous Colitis

THE TENDENCY for gallium citrate Ga 67 to localize in inflammatory lesions can provide an extremely useful, noninvasive test in the septic patient.1-4As with any diagnostic test, associated conditions that can compromise the diagnostic value of67Ga scanning should be known. We recently had a patient with pseudomembranous colitis with a colonic accumulation of67Ga, which to our knowledge, has not been previously reported. Report of a Case A 71-year-old man was in good health until 24 hours prior to admission, when he first had abdominal pain and vomiting. There was no history of hematemesis, diarrhea, melena, or bright red blood originating from the rectum. On physical examination, the patient had a temperature of 38.5 C (101.3 F) and a distended abdomen with left lower quadrant rebound tenderness. Results of the rest of the examination were unremarkable. All laboratory values were within normal limits. An abdominal

Mechanism of 67Ga Accumulation in Normal Rat Liver Lysosomes

67Ga accumulates in various malignant tumors and parenchymatous tissues. It was found to be associated with the soluble fraction of lysosomes (11). The present work investigates the mechanism of 67Ga accumulation in normal liver cells. Lysosomes were isolated from rat liver after intravenous injection of carrier free 67Ga. The soluble lysosomal fraction was obtained by sonication followed by centrifugation at 105,000 xg for 2 hrs. Gel filtration on Sephadex G 25 superfine was carried out on the soluble lysosomal fraction in order to investigate the stability of the 67Ga-protein complex within the lysosomes under EDTA treatment. After treatment with 1 mM/l EDTA a considerable amount of the protein bound radioactivity was found to be liberated. In further experiments the 67Ga binding lysosomal proteins were fractionated by electrophoresis on 7% polyacrylamide gels (0.5 cm x 5.5 cm). After staining with Coomassie blue 18 separated protein bands were apparent. 67Ga distribution within the gels was assessed by direct counting of radioactivity in gel slices. A considerable amount of the intralysosomal protein bound radioactivity migrated with a relative mobility of 0.36 corresponding to a protein band of molecular weight 85,000--90,000. This peak corresponded to the peak of 67Ga-labelled purified transferrin in control gels. These data were confirmed by immunoelectrophoresis combined with autoradiography: within the soluble lysosomal fraction a slight transferrin line could be identified. We conclude that 67Ga which is transported in the blood by transferrin (23) and taken up by the hepatic cell through endocytosis (32) is accumulated in the lysosomes associated with transferrin and its degraded fragments.

Accumulation of gallium-67 in regions of acute myocardial infarction

The radionuclide gallium-67 has been shown to accumulate in a variety of inflammatory and neoplastic lesions, thereby permitting Identification of these abnormalities by radioisotope imaging. We have found that 67Ga also accumulates selectively in recently infarcted myocardium. Acute myocardial infarction was induced in dogs by ligation of the left anterior descending coronary artery, then 67Ga (3 to 4 mc) was injected intravenously. Hearts were removed 24 hours later, and isotope localization was evaluated by an Anger camera and by autoradiography. In five of eight dogs, 67Ga was found to accumulate preferentially in regions of visible infarction. Tissue creatine phosphokinase (CPK), measured in four of the five dogs, was greatly reduced and white blood cell infiltration was intense in the infarcted region. The infarcts of three dogs without preferential 67Ga uptake showed lesser degrees of CPK reduction and white blood cell infiltration. Localization of 67Ga in regions of acute myocardial infarction was also demonstrable by scanning intact, closed chest dogs. Hearts of two animals with transient (20 minutes) ischemia showed neither 67Ga accumulation nor decreased CPK. Thus, 67Ga localization discriminates infarcted from normal or only transiently ischemic myocardium. Unlike potassium and its analogs, 67Ga scanning does not depend on resolution of “cold” areas nor is it likely to introduce ambiguities due to flow limitation of isotope delivery. For these reasons 67Ga may prove particularly useful in the imaging of acute myocardial infarction in man.

67Ga-Citrate Accumulation by Staphylococcal Abscesses and by Tumors

SummaryThe in vivo uptake of 67Ga-citrate by staphylococcal abscesses in rats has been studied. The high accumulation of calcium and magnesium in the abscess and in the surrounding tissues appears to be responsible for the accumulation of 67Ga. The role of the mast cells in the inflammatory process which leads to a calcification (calciphylaxis) is discussed and related to their possible involvement in the case of tumor transplants.