Nephrotoxicity Evaluation of Indium Phosphide Quantum Dots with Different Surface Modifications in BALB/c Mice

InP QDs have shown a great potential as cadmium-free QDs alternatives in biomedical applications. It is essential to understand the biological fate and toxicity of InP QDs. In this study, we investigated the in vivo renal toxicity of InP/ZnS QDs terminated with different functional groups—hydroxyl (hQDs), amino (aQDs) and carboxyl (cQDs). After a single intravenous injection into BALB/c mice, blood biochemistry, QDs distribution, histopathology, inflammatory response, oxidative stress and apoptosis genes were evaluated at different predetermined times. The results showed fluorescent signals from QDs could be detected in kidneys during the observation period. No obvious changes were observed in histopathological detection or biochemistry parameters. Inflammatory response and oxidative stress were found in the renal tissues of mice exposed to the three kinds of QDs. A significant increase of KIM-1 expression was observed in hQDs and aQDs groups, suggesting hQDs and aQDs could cause renal involvement. Apoptosis-related genes (Bax, Caspase 3, 7 and 9) were up-regulated in hQDs and aQDs groups. The above results suggested InP/ZnS QDs with different surface chemical properties would cause different biological behaviors and molecular actions in vivo. The surface chemical properties of QDs should be fully considered in the design of InP/ZnS QDs for biomedical applications.

Shell-Free Copper Indium Sulfide Quantum Dots Induce Toxicity in Vitro and in Vivo

Semiconductor quantum dots (QDs) are attractive fluorescent contrast agents for in vivo imaging due to their superior photophysical properties, but traditional QDs comprise toxic materials such as cadmium or lead. Copper indium sulfide (CuInS₂, CIS) QDs have been posited as a nontoxic and potentially clinically translatable alternative; however, previous in vivo studies utilized particles with a passivating zinc sulfide (ZnS) shell, limiting direct evidence of the biocompatibility of the underlying CIS. For the first time, we assess the biodistribution and toxicity of unshelled CIS and partially zinc-alloyed CISZ QDs in a murine model. We show that bare CIS QDs breakdown quickly, inducing significant toxicity as seen in organ weight, blood chemistry, and histology. CISZ demonstrates significant, but lower, toxicity compared to bare CIS, while our measurements of core/shell CIS/ZnS are consistent with literature reports of general biocompatibility. In vitro cytotoxicity is dose-dependent on the amount of metal released due to particle degradation, linking degradation to toxicity. These results challenge the assumption that removing heavy metals necessarily reduces toxicity: indeed, we find comparable in vitro cytotoxicity between CIS and CdSe QDs, while CIS caused severe toxicity in vivo compared to CdSe. In addition to highlighting the complexity of nanotoxicity and the differences between the in vitro and in vivo outcomes, these unexpected results serve as a reminder of the importance of assessing the biocompatibility of core QDs absent the protective ZnS shell when making specific claims of compositional biocompatibility.

In Vivo Biotransformations of Indium Phosphide Quantum Dots Revealed by X-Ray Microspectroscopy

Many attempts have been made to synthesize cadmium-free quantum dots (QDs), using nontoxic materials, while preserving their unique optical properties. Despite impressive advances, gaps in knowledge of their intracellular fate, persistence, and excretion from the targeted cell or organism still exist, precluding clinical applications. In this study, we used a simple model organism (Hydra vulgaris) presenting a tissue grade of organization to determine the biodistribution of indium phosphide (InP)-based QDs by X-ray fluorescence imaging. By complementing elemental imaging with In L-edge X-ray absorption near edge structure, unique information on in situ chemical speciation was obtained. Unexpectedly, spectral profiles indicated the appearance of In-O species within the first hour post-treatment, suggesting a fast degradation of the InP QD core in vivo, induced mainly by carboxylate groups. Moreover, no significant difference in the behavior of bare core QDs and QDs capped with an inorganic Zn(Se,S) gradient shell was observed. The results paralleled those achieved by treating animals with an equivalent dose of indium salts, confirming the preferred bonding type of In³⁺ ions in Hydra tissues. In conclusion, by focusing on the chemical identity of indium along a 48 h long journey of QDs in Hydra, we describe a fast degradation process, in the absence of evident toxicity. These data pave the way to new paradigms to be considered in the biocompatibility assessment of QD-based biomedical applications, with greater emphasis on the dynamics of in vivo biotransformations, and suggest strategies to drive the design of future applied materials for nanotechnology-based diagnosis and therapeutics.

The toxicology of indium oxide

Indium oxide (In₂O₃) is a technologically important semiconductor essentially used, doped with tin oxide, to form indium tin oxide (ITO). It is poorly soluble in all so far tested physiologic media. After repeated inhalation, In₂O₃ particles accumulate in the lungs. Their mobilization can cause significant systemic exposure over long periods of time. An increasing number of cases of severe lung effects (characterized by pulmonary alveolar proteinosis, emphysema and/or interstitial fibrosis) in workers of the ITO industry warrants a review of the toxicological hazards also of In₂O₃. The database on acute and chronic toxicity/carcinogenicity/genotoxicity/reproductive toxicity as well skin/eye irritation and sensitization is very limited or even lacking. Short-term and subchronic inhalation studies in rats and mice revealed persistent alveolar proteinosis, inflammation and early indicators of fibrosis in the lungs down to concentrations of 1 mg/m³. Epidemiological and medical surveillance studies, serum/blood indium levels in workers as well as data on the exposure to airborne indium concentrations indicate a need for measures to reduce exposure at In₂O₃ workplaces.

H6phospa-trastuzumab: bifunctional methylenephosphonate-based chelator with 89Zr, 111In and 177Lu

The acyclic chelator H6phospa and the bifunctional derivative p-SCN-Bn-H6phospa have been synthesized using nosyl protection chemistry and evaluated with (89)Zr, (111)In, and (177)Lu. The p-SCN-Bn-H6phospa derivative was successfully conjugated to trastuzumab with isotopic dilution assays indicating 3.3 ± 0.1 chelates per antibody and in vitro cellular binding assays indicating an immunoreactivity value of 97.9 ± 2.6%. Radiolabeling of the H6phospa-trastuzumab immunoconjugate was achieved with (111)In in 70-90% yields at room temperature in 30 minutes, while (177)Lu under the same conditions produced more inconsistent yields of 40-80%. Stability experiments in human serum revealed the (111)In-phospa-trastuzumab complex to be 52.0 ± 5.3% intact after 5 days at 37 °C, while the (177)Lu-phospa-trastuzumab to be only 2.0 ± 0.3% intact. Small animal SPECT/CT imaging using mice bearing subcutaneous SKOV-3 ovarian cancer xenografts was performed, and it was found that (111)In-phospa-trastuzumab successfully identified and delineated small (~2 mm in diameter) tumors from surrounding tissues, despite visible uptake in the kidneys and bone due to moderate chelate instability. As predicted from stability assays in serum, the (177)Lu-phospa-trastuzumab conjugate served as a negative control and displayed no tumor uptake, with high uptake in bones indicating rapid and complete radiometal dissociation and suggesting a potential application of H6phospa in transient lanthanide chelation for bone-delivery. Radiolabeling with (89)Zr was attempted, but even with elevated temperatures of 37 °C, the maximum observed radiometal incorporation over 18 hours was 12%. It can be concluded from this work that H6phospa is not superior to the previously studied H4octapa for use with (111)In and (177)Lu, but improvements in (89)Zr radiolabeling were observed over H4octapa, suggesting H6phospa to be an excellent starting point for elaboration of (89)Zr-based radiopharmaceutical development. To our knowledge, H6phospa is the best desferrioxamine alternative for (89)Zr radiolabeling to be studied to date.

Occupational exposure to indium: what does biomonitoring tell us?

BACKGROUND

The industrial uses of indium, a rare metal with no known physiological role in humans, have increased dramatically over the past 15 years. The results of animal toxicity studies showing pulmonary and systemic effects as well as some reports in workers have created a growing concern about the possible occurrence of toxic effects in exposed workers. Validated biomarkers to assess exposure to indium are not available.

OBJECTIVES

This work aimed at investigating the kinetics of indium in urine (In-U) and plasma (In-Pl) in workers manufacturing In ingots and mainly exposed to hardly water-soluble In compounds. All nine workers from the In department of a large metallurgical concern participated in the study as well as 5 retired workers and 20 controls.

METHODS

Personal breathing zone air was collected throughout the work shift on Monday and Friday. Blood and urine samples were collected, before and after the shift, on the same day as the air sampling and on preshift the next Monday after a non-working week-end. Moreover, rats were given either InCl(3) by intraperitoneal injection or In(2)O(3) by pharyngeal aspiration, In was followed in plasma during 120 days and measured in tissues 120 days after exposure.

RESULTS

Higher In-Pl and In-U concentrations were found in both current (range 0.32-12.61 μg/L plasma; 0.22-3.50 μg/g creat) and former (0.03-4.38 μg/L plasma; 0.02-0.69 μg/g creat) workers compared with controls (<0.03 μg/L plasma; <0.02 μg/g creat). Both biological parameters were highly correlated but no correlation was found between In-air (10-1030 μg/m(3)) and In-Pl or In-U. Normalizing In-U by the urinary creatinine concentration reduced the inter- (from 90% to 70%) and intra-individual variability (from 54% to 35%). In-Pl remained remarkably stable along the working week (inter- and intra-individual variability: 89% and 10%, respectively). Neither In-U nor In-Pl significantly increased during the day or the week. A week-end without occupational exposure was not sufficient to reach the background In-Pl and In-U levels measured in controls. The results of the experimental investigations confirmed the hypothesis that inhalation of hardly soluble In compounds may cause accumulation of In in the body leading to a prolonged "endogenous exposure" from both a lung depot of "insoluble" particles that are progressively absorbed and from a retention depot in other internal organs.

CONCLUSION

This study shows that in workers exposed to hardly soluble In compounds, In-U and In-Pl are very sensitive to detect exposure and mainly reflect long-term exposure. In-Pl levels are particularly stable for a given individual. In-U might be more influenced than In-Pl by recent exposure. Both parameters remained high years after withdrawal from exposure, indicating a possible endogenous exposure and a prolonged risk of pulmonary and systemic diseases even after work exposure has ceased.

[Intestinal and hepatic subcellular localization of aluminium and indium administered orally to rat]

Aluminium and indium are two elements used in industrial and medical fields. The purpose of this work was to study the subcellular localization of these elements, after their single and simultaneous oral administration to rats. 2h after the administration of these two elements, the small intestine and the liver were removed.Ultrastructural study showed the presence of electron dense deposits in the lysosomes of apical parts of duodenal enterocytes. When the minerals were administered simultaneously, deposits were observed in lysosomes of duodenal and jejunal enterocytes. No deposits were seen in the hepatic tissue of treated and control rats. Microanalysis identification showed that the deposits are constituted of aluminium, indium as well as phosphorus. Our results suggested that the elements are concentrated, in lysosomes, under the form of insoluble phosphate salts and it seemed that there are no specific lysosomes for the concentration of minerals since the two elements were concentrated in the same lysosome when they are administered simultaneously.

In vivo distribution and fractionation of indium in rats after subcutaneous and oral administration of [114mIn]InAs

Two in vivo experiments were carried out in this study. In the first experiment five rats were given two subcutaneous injections of [(114m)In]InAs. Major sites of accumulation were spleen, liver and kidney. The intracellular distribution of indium was examined by differential centrifugation. The cytoplasmic fraction contained most of the indium activity followed by the mitochondrial fraction. Both outcomes are in close agreement with the results obtained in previous studies. Chromatographic separations on a preparative size exclusion column were carried out. It was shown that indium was mostly bound to high molecular mass compounds in serum and in the cytoplasmic fraction of spleen, liver and kidney. In a second experiment five rats were given four oral doses of [(114m)In]InAs over a short period. Prior to this experiment the in vitro solubility of cold InAs in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) was determined using graphite furnace atomic absorption spectroscopy. In the case of the SGF only 1.3% of an InAs suspension dissolved after 48 hours incubation at 37 degrees C. InAs was not soluble in SIF. Uptake of InAs after oral administration was minimal (<1%). Due to incomplete removal of traces of [(114m)In]InAs from the gastrointestinal tract, it was impossible to calculate accurately the in vivo distribution over the different organs. As the uptake and consequently the activity in the organs were very low, no further chromatographic separations could be carried out. Considering this very low uptake, it can be concluded that InAs will not accumulate in the body after oral exposure.

Pattern of111in-chloride bone marrow scintigraphy in myelodysplastic syndrome; comparison with clinical characteristics

111In-chloride bone marrow scintigraphy (bone marrow scintigraphy) was performed in patients with myelodysplastic syndrome (MDS), tracer accumulation was classified into patterns, and the relationship between the accumulation patterns and prognostic factors was investigated to assess the usefulness of bone marrow scintigraphy. The subjects were 14 patients diagnosed with MDS. Accumulation of the bone marrow scintigraphy tracer was classified according to the degree of accumulation in the axial bone marrow and peripheral expansion. International Prognostic Scoring System (IPSS), which are frequently used for prognostic evaluation of MDS, and conversion to leukemia were investigated in prognostic factors. We also investigated the relationship between enlargement of the liver and spleen and the prognostic factors. The accumulation patterns were as follows: pattern I, The normal accumulation pattern (2 cases); pattern II, the expanded accumulation pattern (6 cases); pattern III, low accumulation pattern (5 cases); and pattern IV, heterogeneous accumulation pattern (1 case). The relationships between the two prognostic factors and accumulation patterns were investigated, and the prognosis was found to be significantly poorer in the patients with the low accumulation pattern than the expanded accumulation pattern. Enlargement of the liver and spleen was not significantly correlated with the prognostic factors.

Preclinical characterisation of 111In-DTPA-trastuzumab

Trastuzumab (Herceptin) is a recombinant humanised IgG1 monoclonal antibody against the human epidermal growth factor receptor 2 (HER2), used for metastatic breast cancer treatment. Radiolabelled trastuzumab may have several future applications for diagnostic use. The aim of the present study was to develop clinical grade (111)Indium ((111)In) radiolabelled trastuzumab, to evaluate the stability and immunoreactivity of the tracer and to perform a biodistribution study in human tumour-bearing mice. Trastuzumab was radiolabelled with (111)In using DTPA as a chelator. (111)In-DTPA-trastuzumab (labelling yield 92.3+/-2.3%, radiochemical purity 97.0+/-1.5%) is stable in PBS when stored at 4 degrees C for more than 14 days. The immunoreactive fraction determined by cell-binding assays, using the HER2-overexpressing human ovarian SK-OV-3 tumour cell line, was 0.87+/-0.06. Biodistribution and tumour targeting were studied in HER2 receptor-positive and -negative tumour-bearing athymic mice. The HER2-positive tumour showed (9.77+/-1.14% injected dose per gram (ID g(-1))) substantial uptake of the labelled antibody already after 5 h. The difference in uptake between HER2-positive versus -negative tumours was even more pronounced 3 days after injection (16.30+/-0.64% ID g(-1)), and was visualised by radioimmunoscintigraphy. Liver, spleen and kidney showed marked tracer uptake. In summary, trastuzumab can be efficiently radiolabelled with (111)In with high labelling yields and high stability. (111)In-DTPA-trastuzumab selectively binds to the human HER2 receptor both in vitro and in vivo in animals. Therefore, (111)In-DTPA-trastuzumab appears suitable for clinical use.

Radiolabeled alpha-melanocyte-stimulating hormone analogs for receptor-mediated targeting of melanoma: from tritium to indium

Following the first synthesis of tritiated alpha-melanocyte-stimulating hormone (alpha-MSH, alpha-melanotropin) in 1974 by Medzihradszky et al., several alpha-MSH analogs were designed containing between 2 and 12 tritium atoms, the latter of which displayed a specific radioactivity of 12.21 GBq/micromol (330 Ci/mmol). Similarly, radioiodinated alpha-MSH analogs of high purity, full biological activity and a specific radioactivity of approximately 140 GBq/micromol were obtained. Although tritiated and radioiodinated alpha-MSH became indispensable tools as tracer molecules for numerous in vitro and in vivo studies, above all for receptor identification and characterization as well as for structure-activity studies, they did not fulfill the criteria required for therapeutic in vivo targeting of metastatic melanoma. Therefore, we recently developed alpha-MSH analogs containing the universal metal chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) in different positions of the molecule. As DOTA can equally well incorporate diagnostic (e.g. (111)In, (67,68)Ga) and therapeutic (e.g. (90)Y, (67)Cu) radionuclides, DOTA-MSH compounds may serve for both melanoma scintigraphy and therapy. The analog DOTA-[betaAla(3), Nle(4), Asp(5), D-Phe(7), Lys(10)]-alpha-MSH(3-10) (DOTA-MSH(OCT)), which contains the metal chelator at its N-terminal end, displayed good in vitro MC1R affinity (IC(50) 9.21 nm). In vivo, [(111)In]DOTA-MSH(OCT) exhibited a favorable biodistribution profile after injection in B16-F1 tumor-bearing mice. The radiopeptide was rapidly cleared from blood through the kidneys and, most importantly, accumulated preferentially in the melanoma lesions. Lung and liver melanoma metastases could be clearly imaged on tissue section autoradiographs 4 h after injection of [(111)In]DOTA-MSH(OCT). A comparative study of [(111)In]DOTA-MSH(OCT) with [(111)In]DOTA-[Nle(4), D-Phe(7)]-alpha-MSH ([(111)In]DOTA-NDP-MSH) demonstrated the superiority of the DOTA-MSH(OCT) peptide, particularly with respect to the amount of radioactivity taken up by non-malignant organs, including bone, the most radiosensitive tissue. These results demonstrate that [(111)In]DOTA-MSH(OCT) specifically targets melanoma metastases and represents a lead compound for the development of therapeutic DOTA-MSH analogs.

Uptake, localization, and dosimetry of 111in and 201tl in human testes

This study concerns the testicular uptake and dosimetry of Auger electron-emitting radionuclides that are used during routine diagnostic nuclear medicine procedures. To consider the possible effects of these radionuclides on spermatogenic cells, a study has been undertaken to obtain in vivo data for quantification of (111)In chloride and (201)Tl chloride uptake into the human testis after intravenous administration. Values have been determined for uptake into the testis as a whole and to the seminiferous tubules where the germ cells are located.

METHODS

Data were obtained from patients with prostate cancer who opted for orchidectomy to effect hormone suppression. Patients were administered intravenously 1.5 MBq of either (111)In chloride or (201)Tl chloride at 24 or 48 h before orchidectomy. Upon removal, the testes were analyzed to assess uptake of radionuclide. Conventional dosimetry has been used to estimate testicular radiation doses using our values of percentage uptake.

RESULTS

Uptake of both (111)In chloride and (201)Tl chloride into the testes was seen at a level above that explained by simple homogeneous distribution of the radionuclide throughout the body; the testes as a whole demonstrated increased uptake by factors of 3.56 and 4.01 compared with nonspecific uptake for (111)In and (201)Tl, respectively, at 24 h after administration. Both radionuclides gained access to the seminiferous tubules.

CONCLUSION

The results obtained indicate that the values of testicular radiation doses quoted by the International Commission on Radiological Protection for (111)In might be too low by a factor of 4, whereas those for (201)Tl might be too high by a factor of 4. No data were obtained for uptake by individual germ cells within the testis and, therefore, no consideration of dosimetry at the cellular level was possible. However, it has been demonstrated that uptake of diagnostic Auger electron-emitting radionuclides by male germ cells within the testis is possible after intravenous administration.

Radioimmunotherapy of non-Hodgkin's lymphoma with 90Y-DOTA humanized anti-CD22 IgG (90Y-Epratuzumab): do tumor targeting and dosimetry predict therapeutic response?

A DOTA (1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid)-conjugated, (111)In- and (90)Y-labeled humanized antibody to CD22, epratuzumab, was studied in patients with non-Hodgkin's lymphoma (NHL) to assess biodistribution and tumor targeting, pharmacokinetics, dosimetry, and anti-antibody response. Of particular interest was to evaluate whether pretherapy targeting and tumor dosimetry could predict therapeutic responses.

METHODS

Patients received a pretherapy imaging study with (111)In-DOTA-epratuzumab IgG (0.75 mg/kg), followed about 1 wk later with (90)Y-DOTA-epratuzumab starting at a dose level of 0.185 GBq/m(2) (5 mCi/m(2)) in patients who had prior high-dose chemotherapy (group 2), and at 0.370 GBq/m(2) in patients who did not have a prior transplant (group 1), with escalation in 0.185-GBq/m(2) increments.

RESULTS

The effective blood half-life for (111)In-DOTA epratuzumab was 36.1 +/- 7.9 h (n = 25) compared with 35.2 +/- 7.0 h for (90)Y-DOTA-epratuzumab (n = 22). The whole-body half-life for (90)Y-DOTA-epratuzumab estimated from (111)In-DOTA-epratuzumab scintigraphy was 58.3 +/- 4.7 h (n = 20), with urine collection confirming the loss of between 2.2% and 15.9% of the injected activity over 3 d (n = 3). One-hundred sixteen of 165 CT-confirmed lesions were visualized with (111)In-DOTA-epratuzumab. Radiation-absorbed doses to liver, lungs, and kidneys averaged 0.55 +/- 0.13 (n = 17), 0.28 +/- 0.06 (n = 17), and 0.38 +/- 0.07 mGy/MBq (n = 10), respectively, with 0.14 +/- 0.02 and 0.23 +/- 0.04 mGy/MBq delivered to the whole-body and red marrow, respectively. Tumor doses (n = 14 lesions in 10 patients) ranged from 1.0 to as much as 83 mGy/MBq for a 0.5-g lesion (median, 7.15 mGy/MBq). Group 2 patients were more likely to experience significant hematologic toxicities, but doses of up to 0.370 GBq/m(2) of (90)Y-DOTA-epratuzumab were tolerated with standard support measures, whereas patients in group 1 tolerated doses of up to 0.740 GBq/m(2) with the potential for further escalation. Anti-tumor effects were seen in both indolent and aggressive NHL. The data also suggest that anti-tumor responses of potentially equal magnitude can occur irrespective of tumor targeting and tumor size. Hence, tumor response did not correlate with the radiation dose delivered or with the tumor being visualized by external imaging. An anti-antibody response to epratuzumab was detected by an enzyme-linked immunosorbent assay in only 2 of 16 patients.

CONCLUSION

These results suggest that (90)Y-DOTA-epratuzmab is a promising agent for the treatment of NHL and warrants further study. There was evidence suggesting that in this system, factors other than tumor radiation dose and targeting may be involved in the success of radioimmunotherapy.

(153)Sm(3+) and (111)In(3+) DTPA derivatives with high hepatic specificity: in vivo and in vitro studies

Two DTPA derivatives, a mono-amide derivative containing an iodinated synthon, DTPA-IOPsp (L(1)) and the ligand DTPA(BOM)(3) (BOM=benzyloxymethyl) (L(2)), radiolabelled with (153)Sm(3+) and (111)In(3+), were studied as potential hepatospecific gamma scintigraphic agents. In vivo studies with Wistar rats show that the main excretory pathway for all the chelates studied is the hepatobiliary system. The complexes of L(2) show even greater hepatobiliary specificity than L(1), perhaps as a consequence of longer blood circulation times due to their strong affinity towards HSA. The (153)Sm(3+) chelates are also more hepatospecific than the corresponding (111)In(3+) chelates. The La(3+) and In(3+) chelates of L(1) and L(2) show some structural and dynamic differences in aqueous solution, as studied by (1)H NMR spectroscopy. While only two nona-coordinated isomers were observed for the La(3+) complexes with both ligands, its number is much larger in the In(3+) complexes, with both octa- and hepta-coordinated species (with unbound side arms), as well as structural isomers for each coordination number.

Alpha-melanocyte-stimulating hormone peptide analogs labeled with technetium-99m and indium-111 for malignant melanoma targeting

BACKGROUND

Previous studies have shown that the compact structure of a rhenium-cyclized alpha--melanocyte-stimulating hormone peptide analog, [Cys3410,D-Phe7]alpha-MSH(3--13), or Re-CCMSH, significantly enhanced its in vivo tumor uptake and retention. In this study, the metal chelate 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) was coupled to the N-terminus of Re-CCMSH in order to develop a melanoma-targeting peptide that could be labeled with a wider variety of imaging and therapeutic radionuclides.

METHODS

Biodistribution properties of indium-111 ((111)In)--labeled DOTA-Re-CCMSH were compared with the non-DOTA-containing technetium-99m ((99m)Tc)--CCMSH in murine melanoma--bearing C57 mice to determine the effects of DOTA on tumor uptake and whole-body clearance. The tumor targeting capacity and clearance kinetics of (111)In-DOTA-Re-CCMSH were also compared with other related cyclic and linear (111)In-labeled DOTA-alpha-MSH complexes.

RESULTS

The in vivo distribution data showed that the conjugation of DOTA to Re-CCMSH did not reduce its initial tumor uptake kinetics but did enhance its tumor retention and renal clearance properties. The tumor uptake of (111)In-DOTA-Re-CCMSH was significantly higher than the other (111)In-DOTA--coupled cyclic or linear alpha-MSH analogs used in this study. Moreover, (111)In-DOTA-Re-CCMSH displayed lower radioactivity accumulation in normal tissues of interest than its non-Re-cyclized counterpart, (111)In-DOTA-CCMSH; the disulfide bond--cyclized (111)In-DOTA-CMSH; or the linear (111)In-DOTA-NDP.

CONCLUSIONS

Peptide cyclization via rhenium coordination significantly enhanced the tumor targeting and renal clearance properties of DOTA-Re-CCMSH, making it an excellent candidate for melanoma radiodetection and radiotherapy.

The effect of prenatal indium chloride exposure on chondrogenic ossification

Daily indium chloride doses of control (0) or 400 mg/kg were administered orally to pregnant Sprague-Dawley (SD) rats by gavage, on d 20 of gestation. Indium concentration was determined in the maternal and fetal blood, livers, kidneys, skulls, and femurs by atomic absorption spectrometry. Further groups of pregnant rats were treated with control (0) or 400 mg/kg indium chloride orally, during the whole gestation period. The fetuses were examined on d 21 of gestation, using histological and histochemical methods. Four hours after the administration indium concentration was found to be significant in the blood, liver, and kidneys of the dams. Twenty-four hours later it increased in the blood but not in the liver and kidney. Fetal indium concentrations were 40-50% of the maternal levels due to a barrier of the placenta. In the skull and the femur, indium was already detectable at 4 h after the administration, and by the end of 24 h, metal concentration was several times higher than that at 4 h, indicating accumulation. Furthermore, it was found that the birefringency of collagen detectable by picrosirius red staining in polarized light around the chondrocytes disappeared and became irregular. In the matrix of the epiphyseal cartilage, the regular, birefringent network demonstrable by Rivanol reaction became irregular and hardly recognizable. In the cytoplasm of the chondrocytes, the diffuse, evenly distributed positive Ricinus communis agglutinin reaction became irregular or disappeared. Similar but much weaker changes were observed with concanavalin A and wheat germ agglutinin stainings. It was concluded that the missing femur and micromelia diagnosed by alizarin staining is the consequence of a specific toxic effect of indium that inhibits chondrogenic ossification. No similar histochemical changes were observed in the bones of the skull developing by desmogenic ossification, despite the presence of indium. Data indicate that the mechanisms of the effects of indium causing retardation and/or malformation differ in the bones developing through desmogenic or chondrogenic ossification.

In vivo distribution and speciation of [114mIn]InCl3 in the Wistar rat

Five Wistar rats were given an intraperitoneal injection of [114mIn]InCl3 during four consecutive days. One hour after the last injection the rats were sacrificed. The in vivo distribution of 114mIn was studied in the blood and in different organs. Differential centrifugation was used to study the distribution in liver, kidney and spleen homogenate. Rat serum, packed cell lysate, urine and the cytosol of liver, kidney and spleen homogenate were examined by size exclusion fast protein liquid chromatography. The results showed that serum accounts for 90% of the indium activity in whole blood. Indium is preferentially accumulated within the liver, spleen and kidney, the highest amount of 114mIn being localised in the cytosolic fraction followed by the mitochondria. Size exclusion experiments showed that, in rat serum, indium is exclusively bound to transferrin. These results differed from earlier in vitro incubation experiments of human serum with 114mIn. It was not possible, from the experiments described herein, to conclude unequivocally whether indium is bound to haemoglobin of packed cell lysate or to another high molecular mass compound. Indium is associated with the high molecular mass fraction in liver, kidney and spleen cytosol; only in kidney are small amounts of 114mIn found in the low molecular mass fraction. The in vivo inhibitory effect of indium on the delta-aminolaevulinic acid dehydratase (ALAD) enzymatic activity in red blood cells and kidney tissue, well documented by other researchers, could not be attributed to direct binding of indium with this enzyme.

Progressive nuclear translocation of somatostatin analogs

Optimal cancer radiotherapy using Auger electron emitters requires selective localization of radionuclides in close proximity to tumor DNA.

METHODS

Intracellular trafficking of (125)I-Tyr1-somatostatin-14 somatotropin-release inhibiting factor (SRIF) and 2 of its analogs, (125)I-WOC 4a and (111)In-pentetreotide, was studied in human neuroblastoma cells.

RESULTS

After 24-h incubation, SRIF was degraded or recycled, whereas its protease-resistant analogs progressively accumulated in nuclear fractions. (111)In-pentetreotide binding to DNA increased over time in somatostatin receptor-positive cells but not in somatostatin receptor-negative cells.

CONCLUSION

These in vitro studies show that prolonged exposure to radiolabeled SRIF analogs significantly increases their cellular internalization, nuclear translocation, and DNA binding. Clinically, infusion of radiolabeled somatostatin analogs may enhance tumor uptake and retention and provide more effective in situ radiotherapy.

Embryotoxic and teratogenic effects of indium chloride in rats and rabbits

Daily indium chloride doses of control (0), 50, 100, 200, or 400 mg/kg were administered orally to Sprague-Dawley rats by gavage, on d 6-15 of gestation, and daily metal doses of control (0), 50, 100, or 200 mg/kg were administered to New Zealand rabbits on d 6-20 of gestation. Further groups of pregnant rats were treated with control (0) or 400 mg/kg indium chloride orally on one of d 8, 9, 10, 11, 12, 13, 14, or 15 of gestation. The dams and fetuses were examined on d 21 (rats) and 30 (rabbits) of gestation, using standard teratological methods. Indium concentration was determined in the maternal and fetal blood, as well as in the amniotic fluid, by atomic absorption spectrometry. Indium was found to cross the placenta and appeared in fetal blood in proportion to the metal concentration of the maternal blood. In the amniotic fluid, indium concentrations remained below the detection limit. In rats, indium chloride produced dose-dependent maternal toxic effects, with a dose of 400 mg/kg inducing embryotoxicity (embryolethality) and teratogenicity. Doses of 200 and 100 mg/kg were embryotoxic (retarding) and teratogenic, causing skeletal and visceral anomalies in addition to external anomalies (rudimentary or missing tail, syndactylia, clubfoot, exencephalia) in rats. In rabbits, 200 mg/kg indium chloride was lethal for the dams and the embryos (some of the animals died, and the number of abortions and full resorptions increased). This dose was found to be teratogenic (caused gross renal anomalies) and increased the frequency of fetuses with skeletal retardation. In rats, the effects of indium chloride causing fetal retardation was found to be independent of exposure time. The teratogenic effects were the highest on d 11 and 12 of gestation, when indium chloride caused gross external malformations. Data suggest that the teratogenic effects of indium chloride can be attributed primarily to a direct cytotoxic action of indium resulting from placental transfer, but the effect is not a selective one, as it appears only in the presence of maternal toxic effects.

Localization of indium-111 in human malignant tumor xenografts and control by chelators

The kinetics of soluble indium-111 ((111)In) in human malignant tumor xenografts and cells was investigated in combination with chelators. Firstly, without chelator, the kinetics of (111)In-chloride was investigated in vitro and in vivo using four human malignant neuroblastoma SK-N-MC, pulmonary papillary adenocarcinoma NCI-H441, pulmonary squamous cell carcinoma PC 9, and colon adenocarcinoma LS 180 cells and xenografts. (111)In was incorporated into tumor cells in vitro to a maximum level during a 60-min incubation. A maximum level of radioactivity was demonstrated in vivo in four human malignant tumors xenografted into nude mice at 24 h postinjection of (111)In-chloride. Secondly, the effect of edetate calcium disodium (CaNa2EDTA) on radioactivity in (111)In-labeled tumors xenografts and cells was studied in vitro and in vivo. CaNa2EDTA significantly reduced (111)In-activity from the labeled tumor xenografts, whereas it had no affect on the radioactivity in the labeled cells. Thirdly, the effect of CaNa2EDTA on radioactivity in human malignant tumors xenografted into nude mice injected with (111)In-chloride was investigated. In one group of mice CaNa2EDTA administered intraperitoneally at 1, 22, 34, 46, 58, and 70 h after injection of (111)In-chloride (postadministration), the localization of (111)In at the tumors was significantly decreased at 72 h compared with the control in all four tumor types. In the other group of mice, CaNa2EDTA administered intraperitoneally at 12 and 1 h before injection of (111)In-chloride and 1, 22, 34, 46, 58, and 70 h postinjection (pre- and postadministration), the radioactivity of tumors was also significantly decreased at 72 h, and the reduction was greater than that with use of postadministration. In a comparative study, CaNa3DTPA had a more powerful effect than CaNa2EDTA. In conclusion, (111)In-activity in tumors consists of intracellular and extracellular components, and the extracellular (111)In may be cleared by chelators. Pre- and postadministration of CaNa3DTPA could remove (111)In-nonspecific localization in tumors when (111)In is released from the radiolabeled agents.

Direct labeling of macroaggregated albumin with indium-111-chloride using acetate buffer

Indium-111-labeled macroaggregated albumin (MAA) would be suitable for combined pulmonary perfusion and ventilation scan using a 99mTc ventilation agent.

METHODS

MAA suspended in 0.1 M sodium acetate buffer, pH 5.8, was incubated with 111In-chloride for 30 min at room temperature. An in vitro study of the obtained 111In-MAA was performed for labeling efficiency and stability in human normal serum. The 111In-MAA was intravenously injected into normal mice, and the biodistribution was studied at 15 and 180 min postinjection. A gamma camera image was obtained at 15 min after injection.

RESULTS

MAA was directly and stably labeled with 111In-chloride, and the labeling efficiency of the preparation was more than 96%. More than 90% of the administered 111In-MAA was caught in the murine lung. The scintigraphy with 111In-MAA showed a clearly visualized murine lung.

CONCLUSION

Indium-111-MAA can be conveniently prepared by direct labeling at room temperature. It provides an alternative perfusion tracer for combined perfusion-ventilation imaging.

Scintigraphic evaluation of four dogs with protein-losing enteropathy using 111indium-labeled transferrin

The purpose of this study was to determine the clinical utility of 111In-labeled transferrin (111In-TF) scintigraphy for evaluating dogs suspected of having protein-losing enteropathies. Four dogs were injected intravenously with autologous 111In-TF after 30 min incubation (at 37 degrees C) of 18.5 MBq (0.5 mCi) 111InCl3 with one ml of autologous plasma. Serial right lateral, left lateral and dorsal images were obtained 2, 4, and 24 hours post 111In-TF administration. Images were subjectively evaluated for the presence or absence of 111In-TF within the gastrointestinal tract. The results of total protein, albumin and globulin levels and results from gastrointestinal biopsies were recorded. In one dog, a follow-up scintigraphic study was done six months after initial evaluation and initiation of treatment for plasmocytic-lymphocytic enteritis. Gastrointestinal activity was noted by two hours in two dogs, while all four dogs had gastrointestinal activity on the 24 hour images. The mean (+/-std dev) plasma protein, albumin and globulin levels were 3.5 (+/-0.9), 1.7 (+/-1) and 1.8 (+/-0.3) respectively at the time of initial presentation. In the one dog that was evaluated after therapy, faint visualization of radioactivity within the colon was noted on the 24 hour image. Based on this study, 111In-TF appears to be a viable scintigraphic method for evaluating dogs with suspected protein-losing enteropathies. Potential limitations of this radiopharmaceutical include cost and prolonged isolation of the animal prior to release to the client due to the long physical half-life (T1/2 = 2.82 days).

Toxicity of a low level of indium phosphide (InP) in rats after intratracheal instillation

To clarify the instillation toxicity of low level of indium phosphide (InP), 0, 1.2, 6.0 and 62.0 micrograms/kg body weight of InP particles were instilled intratracheally in male Fischer 344 rats, and the effects of InP were examined on the following day (day 1) and on the 8th day (day 8) after instillation. Indium was measured but not detected in the serum, liver, kidney, spleen, thymus and brain. Dose-related mild elevation of superoxide dismutase (SOD) activity and lactate dehydrogenase (LDH) activity in bronchoalveolar lavage fluid (BALF) were found on day 1 without increases of inflammatory cells and total protein (TP) in BALF, which suggested the response of neutrophils and alveolar macrophages to instilled InP, and/or the manifestation of a very early stage of inflammation. Only in the 62.0 micrograms/kg-instilled group on day 8, were neutrophils, lymphocytes, TP, LDH, total phospholipid and total cholesterol in BALF increased, and desquamation of alveolar epithelial cells and amorphous exudate in alveolar lumen observed by histopathological examination. These results suggested that InP caused pulmonary inflammation and epithelial cell damage up to 8 days following instillation dose of 62.0 micrograms/kg, but that its effect was considered irrelevant at instillation doses of 6.0 micrograms/kg or below in rat.

Uptake of indium-111-labeled platelets and indium-111 oxine by murine kidneys after total-body irradiation

Radiation nephropathy is a well-known late manifestation of renal irradiation in human beings and experimental animals. Its pathogenesis is unclear, but vascular injury may play a role. Endothelial cells have been demonstrated to manifest a variety of abnormalities within hours of exposure to radiation. In the present experiments mice were exposed to lethal doses of whole-body radiation, and the distribution of 111In-labeled platelets was evaluated during the first week after irradiation. The purpose was to determine if early abnormalities of endothelial cells would be manifested by altered sequestration of platelets in kidneys and other organs. It was found that the indium accumulated in the kidneys of irradiated mice to a greater extent than in nonirradiated mice, supporting the possibility of early vascular injury. In control experiments, administration of 111In-oxine was also followed by excessive accumulation of radioactivity in kidneys of irradiated mice, but the pattern of accumulation differed from that seen after injection of radiolabeled platelets. Renal hyperemia was not demonstrable with 51Cr-labeled red cells, renal vascular permeability was not detected with 125I-labeled albumin, and the pattern of renal uptake of plasma proteins labeled with 59Fe or 111In did not coincide with that seen from 111In administered as labeled platelets or oxine. Renal uptake of 111In-oxine was not associated with alterations in urinary or fecal excretion or an increase in total-body retention of the radioisotope. The findings are consistent with the notion that renal vascular injury at the time of irradiation results in accumulation of platelets or platelet constituents during the first week after total-body irradiation of mice.

New hydroxybenzyl and hydroxypyridylmethyl substituted triazacyclononane ligands for use with gallium(III) and indium(III)

The 67Ga(III) and/or 111In(III) complexes of four new hexadentate ligands have been prepared and evaluated in vitro and in vivo. These substituted triazacyclononane ligands bind the metal ion through three tertiary ring nitrogens and three oxygens from pendant phenolic or hydroxypyridyl arms. The hydroxypyridyl moieties increase the aqueous solubility of the metal complexes while retaining a lipophilic character. As indicated by their large positive partition coefficients, the phenolic ligands proved to be significantly more lipophilic than the hydroxypyridyl ligands. Biodistribution in Sprague-Dawley rats indicated that the more lipophilic phenolic complexes cleared the body primarily through the liver, while the less lipophilic hydroxypyridyl complexes cleared rapidly, primarily through the kidney. To differentiate the clearance characteristics of these radiolabeled compounds, radiochemical purity of selected complexes in vivo was measured. The complexes were evaluated for overall charge in vitro and in vivo, in plasma samples. In addition, plasma and urine were analyzed for possible metabolites. With one exception, each complex was unmetabolized in vivo. All complexes and metabolites formed were neutral in vitro and in vivo. Extended stability in serum of selected radiometal complexes has been measured. Each complex measured was stable to exchange with transferrin, up to 72 h, as expected from the large stability constants of the complexes. The clearance characteristics of the hydroxypyridyl and phenolic ligands, however, were markedly different. The rapid hepatic clearance of the phenolic ligands indicates potential as bifunctional chelates for Ga(III) or In(III).

The reproductive and developmental toxicity of indium in the Swiss mouse

Indium is increasingly used in a variety of industries, and while there are few studies of its developmental toxicity, ther are no reports of its potential reproductive toxicity. These studies were undertaken to investigate the possible reproductive toxicity of indium and to determine the relative vulnerability of males and females. We used, initially, a 21-day combined developmental/reproductive toxicity protocol. Oral exposures to InCl3 ( < or = 250 mg/kg) were without effect on the male reproductive system or liver. A kidney effect was demonstrated in males by a decrease in urinary N-acetyl glucosaminidase. The ability of females to become pregnant was unaffected. However, fetal development was adversely affected, manifested as increased intrauterine deaths in the presence of reduced maternal weight gain. A developmental toxicity study identified no increase in fetal malformations, but verified the increased fetal deaths, in the absence of effects on adjusted maternal body weight. In vitro toxicity studies showed that the embryolethality was at least in part a result of direct toxicity to the conceptus, with effective doses in the low micromolar range. A limited disposition study showed that fetuses contained low micromolar concentrations of indium, more indium than maternal liver, and comparable to levels that were toxic in vitro. Although studies of greater exposure duration are required for risk assessment, these data indicate that fetal development is likely to be more affected by indium than female or male reproduction, with adverse effects occurring at low micromolar levels in vivo and at exposures that may or may not affect body weight.

Tissue distribution and elimination of indium in male Fischer 344 rats following oral and intratracheal administration of indium phosphide

The use of indium phosphide (InP) in the semiconductor industry has raised concerns about potential occupational exposure. The tissue distribution and elimination of indium were investigated in adult male Fischer 344 rats following either a single or 14 consecutive daily oral doses, or following an intratracheal instillation of InP (10 mg/kg). The concentrations of indium ions in blood, urine, feces, and tissues were quantified either using direct acid digestion followed by electrothermal atomic absorption spectrophotometry (ET-AAS) or using an extraction method with methyltricapryl ammonium ions to remove indium from the matrix followed by ET-AAS. Indium was poorly absorbed from the gastrointestinal tract in both single and multiple oral dose studies. Upon its absorption, indium was relatively evenly distributed among the major organs such as liver, kidney, lung, spleen, and testes. By 96 h after oral dose treatment, less than 0.11% of the dose of indium was recovered from tissues in the single- or multiple-dose experiment. At 96 h, retention of indium in the body was about 0.36% of the dose (except for lung) following intratracheal instillation of InP. Following oral dose administration, the majority of indium was recovered from the gastrointestinal tract and its contents. The high recovery of indium (73% of the dose) in the feces after intratracheal instillation presumably reflects mucociliary clearance and/or biliary excretion of indium. Urinary indium accounted only for 0.08-0.23% of the dose during a 240-h collection period in both single- and multiple-dose studies. It seems that fecal excretion serves as the major route for indium elimination, and this results from poor absorption. Because of the poor absorption of indium following multiple oral doses or intratracheal instillation of InP, it seems unlikely that indium will accumulate in the body following InP exposure.

Pulmonary toxicity to intratracheally administered indium trichloride in Fischer 344 rats

The use of indium by the semiconductor industry has risen sharply in recent years with the discovery that the electrical properties of compounds such as indium phosphide and indium arsenide are better than those of silicon. However, relatively little is known about its potential to induce lung damage. These studies examined the effect of indium trichloride (InCl3) on the lung. To examine the disposition and removal of InCl3 from the lung, groups of female Fischer 344 rats received a single intratracheal dose of 1.3 mg In/kg as InCl3 and were euthanized after 1, 2, 4, 7, 14, 28, and 56 days at which time lung samples were analyzed for metal content. Furthermore, the histology, hydroxyproline levels, and bronchoalveolar lavage (BAL) fluid cellularity of the lung were studied. In addition, the effect of 0.00016, 0.00325, 0.065, and 1.3 mg In/kg on inflammatory response and BAL fluid cellularity was compared. While a dose as low as 0.00325 mg In/kg was capable of initiating an influx of inflammatory cells, instillation of 1.3 mg In/kg resulted in an inflammatory response that was still evident 56 days later. After 28 days, the lung weight of the InCl3-treated animals was 2.5 times greater than that of the controls. The total cell number in the BAL fluid of the treated animals after 28 days was 32 times higher than that in the control rats. Sixty-seven percent of these cells were granulocytes. Compared to the controls, the hydroxyproline content of the lungs from the InCl3-treated animals were two-fold greater after 28 and 56 days. Furthermore, the levels of fibronectin and TNF alpha present in the BAL fluid of InCl3-treated rats increased sharply during the first 24 hr and remained elevated 56 days later. These data and the histological examination of the lung following InCl3 treatment suggest that InCl3 is capable of causing severe lung damage and the development of fibrosis.

[Evaluation of biodistribution and imaging of atherosclerotic lesions using 111In-labeled low-density lipoprotein]

111In-labeled low-density lipoprotein (LDL) was administered to Watanabe heritable hyperlipidemic rabbits (WHHL group) and control rabbits (control group) to evaluate its biodistribution and scintigraphic images by gamma-camera and radioactivity of each organ. With external imaging, the heart, liver, kidney, bone and spleen of each rabbit were observed. By setting the region of interest, the liver/heart ratio of the WHHL group was significantly lower than that of the control group (p < 0.05), the plasma half life of LDL was longer and radioactivity in blood, heart and aorta was higher in the WHHL group. Each aorta was autoradiographed and significant accumulation of 111In-labeled-LDL was recognized in the aortic arch, bifurcation of intercostal and celiac artery in the WHHL group. By the use of labeled LDL with the combination of gamma-camera, it is capable of detecting the regulation of lipoprotein metabolism and imaging atherosclerotic lesions externally.

[Evaluation of renal uptake on 111InCl3 bone marrow scintigraphy in patients with aplastic anemia and myelodysplastic syndrome]

High renal uptake on bone marrow scan with indium-111 chloride is often shown in patients with bone marrow abnormality. We evaluated the renal uptake on bone marrow scan in 27 cases with aplastic anemia, 20 cases with myelodysplastic syndrome (MDS) and 10 cases with other diseases. The high renal uptake was observed in patients not only with aplastic anemia but also with MDS. The renal uptake correlated with blood transfusion units, unsaturated iron binding capacity (UIBC), blood pool imaging and bone marrow uptake. The renal uptake correlated with UIBC better than with the blood transfusion units. Following mechanism of the renal uptake is proposed that frequent blood transfusion makes low UIBC, and the low UIBC causes the failure to chelate indium with transferrin. The fast blood clearance of un-chelated indium via kidneys is followed. Hypoplastic bone marrow may also play an important role for the high renal uptake because all patients with the high renal uptake could not be explained by above mentioned mechanisms. Caution should be paid to the scans with the high renal uptake because both aplastic anemia and MDS patients show the high renal uptake.

Myocardial uptake of 111In monoclonal antimyosin Fab in detecting doxorubicin cardiotoxicity in rats. Morphological and hemodynamic findings

BACKGROUND

The therapeutic value of doxorubicin (DOX) is limited by its cardiotoxicity, which is dose dependent. To improve the detection of such myocardial damage, this study was designed to determine whether the 111In antimyosin antibody Fab could serve as a marker for cardiotoxicity in treated versus control rats on the basis of comparative morphological and hemodynamic findings.

METHODS AND RESULTS

DOX was administered by intravenous injection to rats at a dose of 3 mg.kg-1.week-1 for 5 weeks. Three weeks after the final injection, an intravenous dose of 111In antimyosin, 740 kBq (20 microCi), was administered, and tissue distribution of the radioisotope (percent kilogram dose per gram) was assessed in 48 hours. Myocardial uptake of radioactivity by both ventricles was more prominent in the DOX-treated rats than in control rats (p < 0.001). The heart-to-blood and heart-to-lung uptake ratios were markedly higher in the treated rats than in controls (p < 0.001). As the severity of the myocardial damage increased, there was a progressive increase in myocardial uptake. There was a strong correlation between the severity of myocardial damage and the ventricular end-diastolic pressure (r = 0.84 and r = 0.83 in the left and right ventricles, respectively). On microscopic immunoautoradiography of the DOX-treated heart, there was a specific immunolocalization of the radiotracer in the injured myocytes but no radioactivity in the control myocytes.

CONCLUSIONS

111In antimyosin antibody appears to be a useful immunoradiotracer in detecting cardiac damage induced by DOX administration and in assessing the severity of cardiotoxicity. These data reinforce the clinical observation that myocardial imaging using 111In antimyosin Fab is able to provide information to guide the course of patients receiving DOX treatment.

TMPHPG: a lipophilic derivative of EHPG for iron, gallium-68 and indium-111 hepatobiliary clearance

TMPHPG (N,N'-trimethylenebis[2-(2-hydroxy-3,5-dimethylphenyl)glycine]) is a derivative of the ligand EHPG (ethylenebis[2-(o-hydroxyphenyl)glycine]) but is more lipophilic and had been synthesized to increase hepatobiliary clearance. 59Fe(III), 68Ga(III) and 111In(III) complexes of this ligand have been investigated as potential imaging agents for MRI, PET and SPECT, respectively. Metal-dependent differences in blood and liver clearance in mature rats have been evaluated.

Accumulation and distribution of ions of group-IIIA elements in the tissues and eggs of the Japanese quail

Solutions of salts of the five Group-IIIA elements were given, intravenously, to mature Japanese quail. By 18 h, the accumulation maxima in the major tissues were: leg bones, 20% for Ga+3 (67Ga label) in estradiol-treated males; liver, 51% for Al+3 (26Al label) in control males; kidneys, 32% for In+3 (114mIn label) in estradiol-treated males; and growing oocytes plus ova, 37% for In. Accumulations of Tl+1 (202Tl label) were 6 times those for Ga or In in the brain and muscles, and .1 times in plasma. The cumulative maxima in egg components over 8 (B; Tl) or 10 (Al; Ga; In) days were B, 23% in albumen; Al, 38%, Ga 27%, In, 43% in yolks; Tl, 12% in shells. The accumulation of thallium in the eggshells markedly exceeded (P less than .001) the deposits of the other IIIA elements in shells, Al being the next highest at .54%.

111In (III) uptake by inflammatory and normal tissues

Tissue distributions of 111In (III) in the rats bearing granuloma, inflammatory tissue induced by turpentine oil, were compared with those of 67Ga. The results showed that indium-111 resembles 67Ga in the manner of uptake by inflammatory and normal soft tissues. The effect of cold-InCl3 on 111In (III) uptake showed that transferrin is not involved in the uptake of 111In (III) into inflammatory tissues but is involved in the uptake into liver and spleen.

Kinetics of indium-111 chloride in chronic myelogenous leukaemia

Indium-111 (111In) bound to transferrin incorporates transferrin receptors which emerge onto the cell membrane of leukaemic cells that have entered into the proliferative status. This study was undertaken to evaluate the kinetics of 111In chloride by counting blood cell radioactivity in five cases of chronic myelogenous leukaemia (CML). Leucocyte radioactivities reached a peak on the third to ninth day after 111In injection. In one case of mild leucocytosis in the early stage of the chronic phase, leucocyte activity was less than 14% of whole blood cell activity throughout the 14 day period. In two cases in the progressive stage of the chronic phase, and in two cases of blast crisis, 44 to 98% of whole blood cell activity at 48 h after 111In injection was occupied by the leucocyte fraction. Platelet radioactivities revealed maximum counts of only 0.1 to 0.4% of the injected dose on the sixth to tenth day. Accordingly, conventional marrow scintigraphy 48 h after 111In chloride injection seems to depict distribution of myelopoiesis rather than erythropoiesis in the progressive stage of the chronic phase and blast crisis in CML in addition to phagocytosis of 111In colloid by reticuloendothelial system.

111In-labelled baboon platelets: the influence of in vivo redistribution and contaminating 114mIn on the radiation dose

In five normal baboons, whole body 111In decreased slowly (t1/2 = 60 days) after the end of platelet lifespan. There was slight elution of radioactivity from the liver and spleen, the important sites of platelet sequestration. A fraction of this eluted radioactivity accumulated in the bone marrow, but also in other tissues. This redistribution did not have a significant effect on the measurement of in vivo platelet kinetics. It did however, diminish the total weighted radiation dose, especially that due to contaminating 114mIn.