Uptake of aluminum and gallium into tissues of the rat

Transport of aluminum and gallium from blood into rat tissues following continuous iv infusion of metals in different chemical forms has been investigated. Tissue uptake of aluminum and gallium was similar and highly dependent on the chemical species of the metals. Aluminum and gallium accumulated in liver and spleen when infused in the chloride form. Raised citrate markedly enhanced aluminum and gallium uptake into renal cortex and bone; in contrast with gallium-transferrin, citrate increased uptake of⁶⁷Ga into renal cortex and bone by 8- and 14-fold respectively. Uptake of⁶⁷Ga with citrate into renal cortex was around 3 times smaller than that of aluminum. The antitransferrin receptor antibody OX-26 enhanced⁶⁷Ga uptake from gallium citrate into all rat tissues.⁶⁷Ga from purified gallium-transferrin was also taken into all tissues in the presence of OX-26, the effect being greatest in renal cortex and bone. No influence of antibody on aluminum transport into rat tissues was, however, observed when aluminum was infused in the citrate form. Therefore, transport of aluminum and gallium into tissues is not similar under all conditions. Transport of each metal occurs into all tissues in the presence of antitransferrin receptor antibody. The potential for such transport is much greater in the case of gallium. Transport of aluminum and gallium citrate complexes appears important especially in the renal cortex and bone.     

Résultats atypiques et faux-négatifs de la scintigraphie au 67Ga et de la TEP-TDM au 18F-FDG chez une patiente avec sarcoïdose et cancer du sein bilateral

We describe the case of a patient with biopsy proven sinonasal sarcoidosis and a bilateral breast cancer that was unknown at the time of ⁶⁷Ga scintigraphy and ¹⁸F-FDG PET-CT. ⁶⁷Ga scintigraphy showed low sensibility in the assessement of sarcoidosis localizations. Conversely, multiple foci of intense ¹⁸F-FDG uptake were assessed suggesting the presence of active granulomatous disease in sinonasal region, rhinopharynx, skin and several peripheral lymphadenopathy, which were not previously detected by conventional evaluation. On the other hand, an atypical focal accumulation of ⁶⁷Ga uptake was showed in right breast parenchyma, proving to be a grade III infiltrating canalar carcinoma coexistent with pleomorphic type, without axillary metastastic lymphadenopathy. Surprisingly, no ¹⁸F-FDG uptake abnormalities were detected in the right breast in correspondence of ⁶⁷Ga pathological uptake. The whole of these results is discussed according to histological nature of the lesions and the data of the literature.     

Studies on 67Ga uptake by mouse granuloma tissues

In connection with the uptake of ⁶⁷Ga into the inflammatory tissues, such as granuloma tissues produced with turpentine oil, the influence of Fe³⁺ on the uptake of ⁶⁷Ga into mouse granuloma and normal tissues and on the uptake of ¹²⁵I-labeled transferrin and ⁵⁹Fe were investigated. Fe³⁺ decreased the uptake of ⁶⁷Ga into the liver and spleen, but had no influence on the uptake of ⁶⁷Ga into the granuloma tissues. The uptake patterns of ¹²⁵I-labeled transferrin and ⁵⁹Fe in the granuloma tissues were not consistent with that of ⁶⁷Ga at all. These results show that the uptake of ⁶⁷Ga into the granuloma tissues occurs in a free, transferrin-unbound form, but into the liver and spleen in a transferrin-bound form.     

Design of Ga–DOTA-based bifunctional radiopharmaceuticals: Two functional moieties can be conjugated to radiogallium–DOTA without reducing the complex stability

From the X-ray crystal structures of Ga–DOTA chelates, we were able to deduce that two free carboxylate groups of the radiogallium–DOTA complex may be utilized for coupling to functional moieties that recognize molecular targets for in vivo imaging without reducing the radiogallium-complex stability. Thus, we designed 2,2′-[4,10-bis(2-{[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,7-diyl]diacetic acid (DOTA-MN2) (7), employing a metronidazole moiety as the recognition site of hypoxic lesions, based on the drug design concept of bifunctional radiopharmaceuticals. Coupling of DOTA-bis(tert-butyl)ester 5 with 1-(2-aminoethyl)-2-methyl-5-nitroimidazole dihydrochloride, followed by deprotection, afforded the required 7 (DOTA-MN2). ⁶⁷Ga-labeling was carried out by reaction of DOTA-MN2 with ⁶⁷Ga-citrate. When ⁶⁷Ga–DOTA-MN2 was incubated in phosphate-buffered saline or mouse plasma, no measurable decomposition occurred over a 24-h period. In biodistribution experiments in NFSa tumor-bearing mice, ⁶⁷Ga–DOTA-MN2 displayed not only a significant tumor uptake, but also rapid blood clearance and low accumulations in nontarget tissues, resulting in high target-to-nontarget ratios of radioactivity. These results indicate the potential benefits of the drug design of ⁶⁷Ga–DOTA-MN2. The present findings provide helpful information for the development of radiogallium-labeled radiopharmaceuticals for SPECT and PET studies.     

Uptake of Gallium-67 in Colonic and Rectal Tumours

The uptake of ⁶⁷Ga in biopsy specimens of normal and abnormal tissue was measured in 20 cases of colonic and rectal disease and the ratio between the ⁶⁷Ga uptake in these diseases and in the normal colon or rectum was determined. Uptake of the isotope was high in most of the 14 primary malignant tumours, being highest in poorly differentiated tumours. This uptake was found to be concentrated at the active tumour edge. Uptake of the isotope was generally low in non-malignant lesions.     

Triaza-based amphiphilic chelators: Synthetic route, in vitro characterization and in vivo studies of their Ga(III) and Al(III) chelates

Radiogallium chelates are important for diagnostic imaging in nuclear medicine (PET (positron emission tomography) and γ-scintigraphy). Micelles are adequate colloidal vehicles for the delivery of therapeutic and diagnostic agents to organs and tissues. In this paper we describe the synthesis and in vitro and in vivo studies of a series of micelles-forming Ga(III) chelates targeted for the liver. The amphiphilic ligands are based on NOTA (NOTA = 1,4,7-triazacyclonoane-N,N′N″-triacetic acid) and bear a α-alkyl chain in one of the pendant acetate arms (the size of the chain changes from four to fourteen carbon atoms). A multinuclear NMR study (¹H, ¹³C, ²⁷Al and ⁷¹Ga) gave some insights into the structure and dynamics of the metal chelates in solution, consistent with their rigidity and octahedral or pseudo-octahedral geometry. The critical micellar concentration of the chelates was determined using a fluorescence method and ²⁷Al NMR spectroscopy (Al(III) was used as a surrogate of Ga(III)), both showing similar results and suggesting that the chelates of NOTAC6 form pre-micellar aggregates. The logP (octanol-water) determination showed enhancement of the lipophilic character of the Ga(III) chelates with the increase of the number of carbons in the α-alkyl chain. Biodistribution and γ-scintigraphic studies of the ⁶⁷Ga(III) labeled chelates were performed on Wistar rats, showing higher liver uptake for [⁶⁷Ga](NOTAC8) in comparison to [⁶⁷Ga](NOTAC6), consistent with a longer α-alkyl chain and a higher lipophilicity. After 24 h both chelates were completely cleared off from the tissues and organs with no deposition in the bones and liver/spleen. [⁶⁷Ga](NOTAC8) showed high kinetic stability in blood serum.     

Development and characterization of a 68Ga-labeled A20FMDV2 peptide probe for the PET imaging of αvβ6 integrin-positive pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is known to be one of the most lethal cancers. Since the majority of patients are diagnosed at an advanced stage, development of a detection method for PDAC at an earlier stage of disease progression is strongly desirable. Integrin α_Vβ6 is a promising target for early PDAC detection because its expression increases during precancerous changes. The present study aimed to develop an imaging probe for positron emission tomography (PET) which targets α_Vβ6 integrin-positive PDAC. We selected A20FMDV2 peptide, which binds specifically to αvβ6 integrin, as a probe scaffold, and ⁶⁸Ga as a radioisotope. A20FMDV2 peptide has not been previously labeled with ⁶⁸Ga. A cysteine residue was introduced to the N-terminus of the probe at a site-specific conjugation of maleimide-NOTA (mal-NOTA) chelate. Different numbers of glycine residues were also introduced between cysteine and the A20FMDV2 sequence as a spacer in order to reduce the steric hindrance of the mal-NOTA on the binding probe to αVβ6 integrin. In vitro, the competitive binding assay revealed that probes containing a 6-glycine linker ([^natGa]CG6 and [^natGa]Ac-CG6) showed high affinity to αVβ6 integrin. Both probes could be labeled by ^67/68Ga with high radiochemical yield (>50%) and purity (>98%). On biodistribution analysis, [⁶⁷Ga]Ac-CG6 showed higher tumor accumulation, faster blood clearance, and lower accumulation in the surrounding organs of pancreas than did [⁶⁷Ga]CG6. The α_Vβ6 integrin-positive xenografts were clearly visualized by PET imaging with [⁶⁸Ga]Ac-CG6. The intratumoral distribution of [⁶⁸Ga]Ac-CG6 coincided with the α_Vβ6 integrin-positive regions detected by immunohistochemistry. Thus, [⁶⁸Ga]Ac-CG6 is a useful peptide probe for the imaging of α_Vβ6 integrin in PDAC.     

68Ga‐labeling of internalizing RGD (iRGD) peptide functionalized with DOTAGA and NODAGA chelators

The dual interaction with integrins and neuropilin‐1 receptor is the peculiar feature of iRGD peptide. Hence, in the present study, two iRGD peptide analogs were synthesized with DOTAGA and NODAGA as bifunctional chelator and aminohexanoic acid as a spacer for radiometalation with ⁶⁸GaCl₃. Negatively charged ⁶⁸Ga‐DOTAGA‐iRGD and neutral ⁶⁸Ga‐NODAGA‐iRGD radiotracers were investigated through in vitro cell uptake studies and in vivo biodistribution studies. Significant internalization of radiotracers in murine melanoma B16F10 cells was observed during in vitro studies. During in vivo studies, tumor uptake was higher for neutral ⁶⁸Ga‐NODAGA‐iRGD, but ⁶⁸Ga‐DOTAGA‐iRGD exhibited better tumor‐to‐blood ratio due to faster blood clearance. High kidney uptake of the two radiotracers was the limitation, which needs to be resolved through modification either in the peptide backbone or spacer/chelator.     

An Improved Method for in Vivo Tracing and Imaging of Liposomes Using a Gallium 67-Deferoxamine Complex

Abstract

We have developed a new method for tracing and imaging liposomes in vivo based on the encapsulation of a gallium 67-deferoxamine ⁶⁷Ga-DF) complex in the liposomal water phase. This method combines several advantages over other published methods: extremely high affinity of ⁶⁷Ga for DF, thus avoiding the problem of metal translocation to various plasma proteins; rapid renal clearance rate of⁶⁷Ga-DF complex, thus minimizing the background of radioactivity in non-liposome-associated form; and use of⁶⁷Ga, a readily available, short half-life gamma-emitter convenient for dosimetry and imaging, which can be efficiently loaded into preformed liposomes.     

Autoradiographic model experiments with 67Ga and 99mTc

Summary In order to evaluate the feasibility to localize correctly ⁶⁷Ga citrate and ^99mTc pertechnetate in tissues, the resolution of these radioactive compounds were measured in a model system using four different autoradiographic techniques, wet as well as dry.Wet autoradiographic techniques gave an almost complete loss of ⁶⁷Ga. In deparaffinized sections of fixed and paraffin-embedded tissue the remaining ⁶⁷Ga, which was probably bound to proteins, gave a resolution of 2.6 . ^99mTc was either completely lost in wet techniques or the procedure could not be performed at all because of the very short half life of ^99mTc.The resolution of ⁶⁷Ga in a dry autoradiographic technique (according to Stumpf) was 6.9 and the resolution of ^99mTc 22.6 .The technique in which frozen sections are thawed on dry film and consequently dryed, gave slightly better resolutions than the dry technique (according to Stumpf) with ⁶⁷Ga as well as ^99mTc.It is concluded that for the histological localization of ⁶⁷Ga and ^99mTc a dry technique is required. However, the use of a wet technique can be considered, provided a loss of the radioisotope is acceptable and the procedure is controlled by a dry technique.     

Biodistribution and tumor uptake of [67Ga]chlorogallium-tetraoctadecyloxy phthalocyanine and its sulfonation products in tumor bearing C3H mice

To evaluate the biodistribution and tumor uptake of chlorogallium tetraoctadecyloxy phthalocyanine, a potential new drug for the photodynamic therapy of cancer, we prepared the radioactive ⁶⁷Ga-labeled complex and its water soluble sulfonated derivative. The non-sulfonated dye was obtained by condensation of octadecyloxyphthalonitrile in the presence of a mixture of ⁶⁷Ga and ⁶⁹Ga chloride. The sulfonated derivative was obtained by treatment of the condensation product with oleum. As singlet molecular oxygen has been implicated in the photodynamic action of phthalocyanines (Pcs), the quantum yield of singlet oxygen (φ_Δ) was evaluated for chlorogallium tetraoctadecyloxy Pc, and also its zinc, aluminum and metal free analogues. After intraperitoneal administration of the non-sulfonated dye into RIF tumor bearing C3H mice, a very high ⁶⁷Ga-uptake was observed in the spleen, while tumor radioactivity remained low during the 3 day study. The in vivo stability of the ⁶⁷Ga-phthalocyanine complex was confirmed by comparing the distribution pattern with that of ⁶⁷Ga-citrate, which proved to be significantly different. Intravenous injection of the sulfonated dye resulted in an overall lowering of ⁶⁷Ga-uptake by most tissues, particularly in the spleen, while tumor radioactivities were slightly higher. These data suggest that amphiphilic photosensitizers, containing both polar sulfonate groups and long aliphatic substituents, exhibit the best distribution pattern for both imaging and photodynamic therapy of tumors.     

Bone morphogenetic protein-7 expression in human pyelonephritis

Bone morphogenetic protein 7 (BMP- 7) is a member of the transforming growth factor (TGF) beta superfamily and is involved in regeneration, repair, and development of specific tissues, for example kidney and skeleton. The experimental studies have shown its protective role against fibrotic processes. Tubulointerstitial changes are present in the pyelonephritic kidney which progresses to fibrosis. Renal fibrosis may lead to the loss of renal function. The aim of this study was to investigate BMP-7 expression in acute and chronic pyelonephritis in humans. Seven patients with acute pyelonephritis and 7 with chronic pyelonephritis were treated in Department of Nephrology Clinical Hospital, Rijeka. Tissue biopsy was taken and renal tissue was studied histopathologically by use of hematoxylin and eosin and scored for diagnosis of pyelonephritis. BMP-7 expression was studied by immunohistochemical staining. BMP-7 expression was observed in the tubular area of the pyelonephritic kidneys. The expression of BMP- 7 was stronger in the acute pyelonephritic group and less in the chronic pyelonephritic group of patients. The results imply that BMP-7 has a role in chronic pyelonephritis. Tubular BMP-7 expression had a negative correlation with fibrosis and tubular, atrophy. Our results are suggesting that BMP- 7 plays an important protective role in renal inflammatory diseases preventing greater damage and fibrosis.     

Effect of angiotensin-II on renal Na/H exchanger-NHE3 and NHE2

The purpose of the present study was to determine the effect of angiotensin II (A-II) on membrane expression of Na⁺/H⁺ exchange isoforms NHE3 and NHE2 in the rat renal cortex. A-II (500 ng/kg per min) was chronically infused into the Sprague-Dawley rats by miniosmotic pump for 7 days. Arterial pressure and circulating plasma A-II level were significantly increased in A-II rats as compared to control rats. pH-dependent uptake of ²²Na⁺ study in the presence of 50 μM HOE-694 revealed that Na⁺ uptake mediated by NHE3 was increased ∼88% in the brush border membrane from renal cortex of A-II-treated rats. Western blotting showed that A-II increased NHE3 immunoreactive protein levels in the brush border membrane of the proximal tubules by 31%. Northern blotting revealed that A-II increased NHE3 mRNA abundance in the renal cortex by 42%. A-II treatment did not alter brush border NHE2 protein abundance in the renal proximal tubules. In conclusion, chronic A-II treatment increases NHE3-mediated Na⁺ uptake by stimulating NHE3 mRNA and protein content.     

Bifunctional 3-hydroxy-4-pyridinone derivatives as potential pharmaceuticals: synthesis, complexation with Fe(III), Al(III) and Ga(III) and in vivo evaluation with 67Ga

A series of extra-functionalized 3-hydroxy-4-pyridinone chelators of hard metal ions, containing different side-chains with peptidomimetic groups, was studied to assess the effect of those groups on the physico-chemical properties, the metal-chelating affinity and the in vivo behaviour of the compounds, in view of their potential pharmaceutical applications. Besides the synthesis of the chelators, the study of their properties in aqueous solution alone and in the presence of M ³⁺ (M = Fe, Ga and Al) was performed by potentiometric/spectroscopic techniques. The octanol/water partition coefficient values of these hydroxypyridinone derivatives cover ca. 3 orders of magnitude (1.1 > log P > −2). They all form very stable tris-chelated M(III) complexes, the pFe and pGa values ranging up to five orders of magnitude. The in vivo studies showed the effect of the ligands on the biodistribution of ⁶⁷Ga citrate and also of ⁶⁷Ga-complexes in mice, in view of the potential use of the ligands or complexes as metal decorporating or as imaging agents, respectively. Although almost all these peptidomimetic hydroxypyridinone derivatives present very rapid clearance rate from most organs, the L-ornithine derivative (H₂L⁹) shows to be superior to the others and as good as Deferiprone as metal decontaminant of Ga. Concerning the ⁶⁷Ga complexes, the benzyl-propylamine (H₂L³) shows considerable bone retention, thus suggesting its potential application as imaging agent.Electronic Supplementary Material Supplementary material is available for this article at An erratum to this article can be found at     

Transferrin-based radiolabeled probe predicts the sensitivity of human renal cancer cell lines to ferroptosis inducer erastin

Ferroptosis induction has been recognized as a novel cancer therapeutic strategy. To effectively apply ferroptosis-targeting cancer therapy to individual patients, a diagnostic indicator for selecting this therapeutic strategy from a number of molecular targeting drugs is needed. However, to date, methods that can predict the efficacy of ferroptosis-targeting treatment have not been established yet. In this study, we focused on the iron metabolic pathway to develop a nuclear imaging technique for diagnosing the susceptibility of cancer cells to ferroptosis. As a nuclear probe, human transferrin (Tf) was labeled with Gallium-68 (⁶⁸Ga) using 2-(p-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) as a chelator (⁶⁸Ga-NOTA-Tf). Western blot assay and clonogenic survival assay with human renal cancer cell lines A498 and 786-O revealed that the protein expression level of transferrin receptor1 (TfR1) and sensitivity to a ferroptosis inducer, erastin, were correlated. A cellular uptake assay with ⁶⁸Ga-NOTA-Tf revealed that the cancer cells sensitive to erastin highly internalized the ⁶⁸Ga-NOTA-Tf. Furthermore, treatment with the TfR1 inhibitor ferristatin II reduced the cellular uptake of ⁶⁸Ga-NOTA-Tf, indicating that the intracellular uptake of the probe was mediated by TfR1. These results suggest that ⁶⁸Ga-NOTA-Tf can be useful in predicting the sensitivity of cancer cells to ferroptosis inducers.     

Development of Novel Radiogallium-Labeled Bone Imaging Agents Using Oligo-Aspartic Acid Peptides as Carriers

⁶⁸Ga (T _1/2 = 68 min, a generator-produced nuclide) has great potential as a radionuclide for clinical positron emission tomography (PET). Because poly-glutamic and poly-aspartic acids have high affinity for hydroxyapatite, to develop new bone targeting ⁶⁸Ga-labeled bone imaging agents for PET, we used 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) as a chelating site and conjugated aspartic acid peptides of varying lengths. Subsequently, we compared Ga complexes, Ga-DOTA-(Asp)_n (n = 2, 5, 8, 11, or 14) with easy-to-handle ⁶⁷Ga, with the previously described ⁶⁷Ga-DOTA complex conjugated bisphosphonate, ⁶⁷Ga-DOTA-Bn-SCN-HBP. After synthesizing DOTA-(Asp)_n by a Fmoc-based solid-phase method, complexes were formed with ⁶⁷Ga, resulting in ⁶⁷Ga-DOTA-(Asp)_n with a radiochemical purity of over 95% after HPLC purification. In hydroxyapatite binding assays, the binding rate of ⁶⁷Ga-DOTA-(Asp)_n increased with the increase in the length of the conjugated aspartate peptide. Moreover, in biodistribution experiments, ⁶⁷Ga-DOTA-(Asp)₈, ⁶⁷Ga-DOTA-(Asp)₁₁, and ⁶⁷Ga-DOTA-(Asp)₁₄ showed high accumulation in bone (10.5±1.5, 15.1±2.6, and 12.8±1.7% ID/g, respectively) but were barely observed in other tissues at 60 min after injection. Although bone accumulation of ⁶⁷Ga-DOTA-(Asp)_n was lower than that of ⁶⁷Ga-DOTA-Bn-SCN-HBP, blood clearance of ⁶⁷Ga-DOTA-(Asp)_n was more rapid. Accordingly, the bone/blood ratios of ⁶⁷Ga-DOTA-(Asp)₁₁ and ⁶⁷Ga-DOTA-(Asp)₁₄ were comparable with those of ⁶⁷Ga-DOTA-Bn-SCN-HBP. In conclusion, these data provide useful insights into the drug design of ⁶⁸Ga-PET tracers for the diagnosis of bone disorders, such as bone metastases.     

Intérêt de la scintigraphie rénale au DMSA dans les pyélonéphrites aiguës de l’enfant

IntroductionAcute pyelonephritis is responsible for significant morbidity during the acute phase and distant irreversible kidney damage. However, diagnosis is often difficult in children. The aim of our study was to evaluate in children hospitalized for suspected acute pyelonephritis prevalence of acute lesions revealed by scintigraphy with ^99mTc labeled dimercaptosuccinic acid (DMSA) and the relationship between renal parenchymal lesions and different clinical factors and biological risks.MethodsThis is a prospective study collecting 40 children admitted with suspected infection of the high urinary tract. All have benefited from DMSA renal scintigraphy.ResultsThe average age of our patients was 3.25 years. The DMSA scan showed signs of acute pyelonephritis in 32.5% of cases. Taking this examination as a reference, fever was the most sensitive clinical signs (76.9%), but the specificity was only 48.1%. CRP (≥ 20 mg/mL) was the most sensitive (92.3%) but with a specificity of 40.7% organic signs. A high CRP was associated with acute pyelonephritis significantly (P = 0.0033). Sixty-three percent of refluxing kidneys were associated with acute pyelonephritis versus 20.8% of non-refluxing kidneys, with a significant difference (P = 0.007).ConclusionIn case of urinary tract infection in children, a complete clinical and laboratory table may be sufficient to retain the diagnosis of acute pyelonephritis. However, this possibility is rare. In the opposite case, a DMSA scan should be performed to confirm the diagnosis.     

Iron-uptake in the Euryarchaeon Halobacterium salinarum

Iron-uptake is well studied in a plethora of pro- and eukaryotic organisms with the exception of Archaea, which thrive mainly in extreme environments. In this study, the mechanism of iron transport in the extremely halophilic Euryarchaeon Halobacterium salinarum strain JW 5 was analyzed. Under low-iron growth conditions no siderophores were detectable in culture supernatants. However, various xenosiderophores support growth of H. salinarum. In [⁵⁵Fe]–[¹⁴C] double-label experiments, H. salinarum displays uptake of iron but not of the chelator citrate. Uptake of iron was inhibited by cyanide and at higher concentrations by Ga. Furthermore, a K_M for iron uptake in cells of 2.36 μM and a V_max of approximately 67 pmol Fe/min/mg protein was determined. [⁵⁵Fe]-uptake kinetics were measured in the absence and presence of Ga. Uptake of iron was inhibited merely at very high Ga concentrations. The results indicate an energy dependent iron uptake process in H. salinarum and suggest reduction of the metal at the membrane level.     

K+ deficiency caused defects in renal tubular cell proliferation,oxidative stress response,tissue repair and tight junction integrity,but enhanced energy production,proteasome function and cellular K+ uptake

Hypokalemia is a common electrolyte disorder in hospitalized patients and those with chronic diseases and is associated with renal tubular injury. Our recent expression proteomics study revealed changes in levels of several proteins in renal tubular cells during K⁺ deficiency. However, functional significance and mechanisms underlying such changes remained unclear. The present study, thus, aimed to investigate functional changes of renal tubular cells induced by K⁺ deficiency. MDCK cells were maintained in normal-K⁺ (ANK; [K⁺] = 5.0 mM), Low-K⁺ (ALK; [K⁺] = 2.5 mM), or K⁺-depleted (AKD; [K⁺] = 0 mM) medium. Cell count and cell death assay showed that ALK and AKD groups had marked decrease in cell proliferation without significant change in cell death. Other functional investigations revealed that AKD cells had significantly increased levels of carbonylated proteins (by OxyBlot assay), impaired tissue repair (by scratch assay), defective tight junction (by Western blotting, immunofluorescence staining and measuring transepithelial electrical resistance), increased intracellular ATP level (by ATP measurement), decreased levels of ubiquitinated proteins (by Western blotting), and increased level of Na⁺/K⁺-ATPase (by Western blotting), which was consistent with the increased cellular K⁺ uptake after K⁺ repletion. Our findings have shown that AKD caused defects in cell proliferation, oxidative stress response, tissue repair and tight junction integrity, but on the other hand, enhanced energy production, proteasome function and cellular K⁺ uptake. These findings may shed light onto cellular response to K⁺ deficiency and better understanding of both pathogenic and compensatory mechanisms in hypokalemic nephropathy.     

A radiogallium–DOTA-based bivalent peptidic ligand targeting a chemokine receptor,CXCR4, for tumor imaging

We have developed a novel radiogallium (Ga)–DOTA-based bivalent peptidic ligand targeting a chemokine receptor, CXCR4, for tumor imaging. A CXCR4 imaging probe with two CXCR4 antagonists (Ac-TZ14011) on Ga–DOTA core, Ga–DOTA-TZ2, was synthesized, and the affinity and binding to CXCR4 was evaluated in CXCR4 expressing cells in vitro. The affinity of Ga–DOTA-TZ2 for CXCR4 was 20-fold greater than the corresponding monovalent probe, Ga–DOTA-TZ1. ⁶⁷Ga–DOTA-TZ2 showed the significantly higher accumulation in CXCR4-expressing tumor cells compared with ⁶⁷Ga–DOTA-TZ1, suggesting the bivalent effect enhances its binding to CXCR4. The incorporation of two CXCR4 antagonists to Ga–DOTA could be effective in detecting CXCR4-expressing tumors.