Thyroid Scanning with 131Cs

Scanning of the thyroid gland after the administration of radioactive caesium (¹³¹Cs) was performed in 45 patients; in 38 of these it had been shown that a thyroid nodule failed to accumulate sodium per-technetate (^99mTc) or sodum iodide (¹³¹I). ¹³¹Cs was concentrated in the nodule to a greater degree than in the paranodular thyroid tissue in seven patients, in five of whom thyroid carcinoma was subsequently identified. In five patients ¹³¹Cs accumulated in both the nodule and paranodular tissue, while in the other 26 no ¹³¹Cs uptake occurred in the nodule. In only one of the latter group was the thyroid lesion malignant. Caesium scanning seems to offer a useful supplementary procedure in the investigation of thyroid nodules.     

Tissue distribution of 131I radiolabeled transferrin in the athymic nude mouse: Localization of a human colon adenocarcinoma HT-29 xenograft

The tissue distribution of ¹³¹I-transferrin (¹³¹I-Tf) was studied in athymic nude mice having s.c. human colonic adenocarcinoma HT-29 xenografts. Four days after ¹³¹I-Tf injection, the ¹³¹I specific activity measured in the HT-29 tumor, i.e. amount of radioactivity per gram of fresh tissue, represented 0.31 ± 0.09% of the injected radioactivity and was 1.90 fold more than that measured in the murine colon (P < 0.05). After correction for intravascular ¹³¹I-Tf as estimated by means of ^99mTc-Sn in vivo labeling of red blood cells, the ¹³¹I specific activity observed in the HT-29 tumor was 7.21 fold more than that observed in the murine colon. This subtracting method enabled us to localize a HT-29 tumor xenograft by γ scintigraphy of the entire animal and demonstrated that ¹³¹I-Tf could be a non-specific but potent marker for human colon cancer.     

The Lack of Selective Reincorporation into Tissue Protein of the Amino Acids Derived from the Catabolism of Serum Protein

Homologous S³⁵-labeled albumin, gamma globulin, and alpha-beta globulin were transfused into rabbits and the specific activities of the electrophoretic fractions of the sera of the recipients were determined at various time intervals up to 12 days after injection. Detectable reincorporation into a fraction other than that transfused was found only in the gamma globulin fraction after albumin injection. This activity rose between 2 and 12 days and reached a level of 2 to 3 per cent of the extrapolated zero time activity of the albumin fraction. When homologous serum protein doubly labeled with I¹³¹ and S³⁵ was transfused into mice, marked drops in the ratios of I¹³¹ to S³⁵ in the serum and tissue proteins were observed between 1 and 48 hours after injection. On the basis of a determination of the absolute and relative amounts of I¹³¹ and S³⁵ found in the various tissue and serum proteins, the amount of reincorporation of S³⁵ into each protein was calculated. The relative amounts of reincorporation of S³⁵ among the various tissues were remarkably similar to the relative amounts of incorporation of S³⁵ after the injection of labeled free amino acids. It is concluded that serum protein does not form a major direct source of amino acids to the tissues but feeds them indirectly through the extracellular pool.     

Frostbite Protection in Mice Expressing an Antifreeze Glycoprotein

Ectotherms in northern latitudes are seasonally exposed to cold temperatures. To improve survival under cold stress, they use diverse mechanisms to increase temperature resistance and prevent tissue damage. The accumulation of anti-freeze proteins that improve cold hardiness occurs in diverse species including plants, arthropods, fish, and amphibians. We previously identified an Ixodes scapularis anti-freeze glycoprotein, named IAFGP, and demonstrated its cold protective function in the natural tick host and in a transgenic Drosophila model. Here we show, in a transgenic mouse model expressing an anti-freeze glycoprotein, that IAFGP protects mammalian cells and mice from cold shock and frostbite respectively. Transgenic skin samples showed reduced cell death upon cold storage ex vivo and transgenic mice demonstrated increased resistance to frostbite injury in vivo. IAFGP actively protects mammalian tissue from freezing, suggesting its application for the prevention of frostbite, and other diseases associated with cold exposure.     

Mutagenicity of diagnostic and therapeutical doses of radiopharmaceutical iodine-131 in Wistar rats

Iodine-131 (¹³¹I) is a radioisotope used for the diagnosis and treatment of thyroidal disorders such as hyperthyroidism and cancer. During its decay, ¹³¹I emits beta particles and gamma rays; its physical half-life is 8 days, and it is accumulated preferentially in the thyroid tissue. This study aimed to evaluate the cytotoxicity and mutagenicity of diagnostic and therapeutic doses of ¹³¹I using bone marrow cells of rats treated in vivo in a test system with a single dose by gavage. Concentrations of 5, 25, 50 and 250 μCi in 1 ml of water were used, and after 24 h, the animals were killed. Also, a concentration of 25 μCi/ml of water was used, and the animals were killed after 5 days. The results showed that no concentration of ¹³¹I was cytotoxic and that all concentrations were mutagenic. As a result, there was no statistically significant difference detected by the χ² test in the induction of chromosomal aberrations between the different doses. Thus, the present study demonstrated a significant increase in chromosomal aberration in bone marrow cells exposed to ¹³¹I regardless of the dose or the treatment time.     

NLR、PLR与分化型甲状腺癌术后131I清甲效果的关系及其预测价值分析

摘要 目的：探讨中性粒细胞/淋巴细胞比值（NLR）、血小板/淋巴细胞比值（PLR）与分化型甲状腺癌（DTC）术后碘131（¹³¹I）清甲治疗效果的关系及对DTC术后¹³¹I清甲效果的预测价值。方法：选择2019年3月至2021年12月在江苏大学附属徐州医院行甲状腺切除术且术后进行¹³¹I清甲治疗的DTC患者150例为研究对象,根据¹³¹I清甲治疗效果分为清甲成功组（107例）和清甲未成功组（43例）,通过检查血常规获得中性粒细胞计数、血小板计数、淋巴细胞计数并计算NLR、PLR,比较两组NLR、PLR;采用单因素及多因素logistics回归模型分析¹³¹I清甲疗效的影响因素,采用受试者工作特征曲线（ROC）分析NLR、PLR对¹³¹I清甲治疗效果的预测价值。结果：清甲成功组NLR、PLR低于清甲未成功组（P＜0.05）,单因素分析显示清甲成功组促甲状腺激素（TSH）高于清甲未成功组,甲状腺球蛋白（Tg）水平低于清甲未成功组,清甲成功组病灶最大径小于清甲未成功组（P＜0.05）;多因素logistics回归分析显示,高NLR、PLR、Tg是¹³¹I清甲治疗失败的独立危险因素（P＜0.05）;NLR、PLR及联合检测预测¹³¹I清甲治疗效果的ROC曲线下面积（AUC）分别为0.760、0.732、0.829,NLR与PLR联合检测的AUC高于二者单独检测。结论：高NLR、PLR是DTC术后¹³¹I清甲未成功的独立危险因素,早期检测NLR、PLR对DTC术后¹³¹I清甲治疗效果具有较好的预测价值。     

Frostbite: Current status and advancements in therapeutics

Frostbite is a severe ischemic injury which occurs due to the tissue vascular damage after sub-zero temperature tissue exposure. Deep frostbite can result in necrosis and may need amputation of affected tissue. Though a serious injury, it is not very well understood, and further scientific exploration is needed. This work explores the current understanding of the pathophysiology of frostbite. We reviewed the current status of the diagnostics, the drugs, the therapies and the surgical practices for prevention and management of frostbite. Advances in nanotechnology and drug delivery had improved the therapeutic outcomes significantly. This review also explored the latest advancements and researches done for development of newer therapeutics and diagnostics for frostbite care.     

Organ localization of intravenously administered HSA I131 in chickens

A study was made on the elimination of heterologous albumin (HSA I¹³¹) from the blood of chickens and on its organ distribution. The elimination curve of heterologous antigen followed the typical three-phase pattern. An accelerated elimination of heterologous albumin as compared to the role of elimination of homologous albumin during the second phase is suggestive of specific uptake of antigen. The elimination curve of homologous albumin showed only two phases. The uptake of HSA I¹³¹ by organs was evaluated with respect to the amount of antigen present in the circulation. The highest cumulation of antigen was found in the liver and spleen after the 5th day following HSA I¹³¹ administration. A mild increase in the antigen content was found already after the 3rd day following injection. The increase in antigen concentration shown by the lung tissue and bone marrow was less marked. The increase in activity found in the bursa of Fabricius and in the thymus is attributed to tissues of other origin which could not be dissected fully from the respective tissue.     

Effect of inhibiting prostaglandin synthesis on edema formation and albumin leakage during thermal trauma in the rat

Prostaglandins (PGs) participate in the inflammatory response, but the contribution of endogenously synthesized PGs to edema formation and increased vascular permeability is not known. Using a 10% scald burn in the rat, we measured water content (as percent, wet minus dry/wet weight) and ¹³¹I-RISA leakage (counts/g dry tissue) in scalded and normal skin at 30 minutes and 3 hr post injury. Four groups (10 rats/group) in each time period studied: control; scald; scald, 5 mg/kg indomethacin; scald, 10 mg/kg indomethacin. Indomethacin was administered intravenously 30 minutes before the scald; RISA was injected intravenously 30 min before termination of the study. In all indomethacin-treated groups immunoreactive plasma PGA was significantly lower (p < 0.05) than in scalded, untreated groups. All scalded groups showed significantly higher RISA counts and water content than did the control group (p < 0.01). At 30 min post-injury the indomethacin-treated groups did not differ from the untreated scald group (p> 0.20). In the 3 hour study all scalded groups had significantly higher content and RISA counts than control (p < 0.01). Thus PGs produced during thermal trauma do not greatly contribute to the edema formation and increase in vascular permeability.     

Discussion on radioactive iodine treatment of hyperthyroidism and the risk of induced cancer

Iodine-131 (¹³¹I, radioiodine) has been used for over eight decades for the treatment of Graves’ disease, either as initial therapy or following failure of thionamides, as well as for the treatment of autonomous thyroid nodules. ¹³¹I treatment is simple to administer, effective, and relatively inexpensive. Recently, there has been some turmoil after a study published in JAMA Internal Medicine reported an increased risk of cancer from ¹³¹I treatment. The impact was of short duration however, as the paper received severe criticisms from many nuclear medicine physicians as well as from endocrinologists. Here we explain why that paper's conclusions are doubtful. We also review the major data on the topic of ¹³¹I therapy of hyperthyroidism and the risk of cancer.     

A Case of Esophageal Stricture After Iodine 131 Ablation

ObjectiveTo report the first case of esophageal stricture as a complication of radioiodine (¹³¹I) ablation therapy.MethodsWe review the medical and surgical history of this patient and discuss various potential causes of the esophageal stricture.ResultsA 79-year-old woman presented with increasing dysphagia and weight loss of about 4.5 kg after recent ¹³¹I therapy for thyroid cancer remnant ablation. Her pertinent history included gastroesophageal reflux disease, an anterior midcervical esophageal web, and a distal esophageal stricture. She also had a history of radiation therapy to her chest for breast cancer about 28 years previously. On the day of ¹³¹I therapy, the 5.5-GBq ¹³¹I capsule lodged accidentally in her midcervical area for approximately 2.5 hours. The resulting radiation dose to the proximal esophagus was estimated to be 7.86 Gy from gamma radiation and possibly as high as several thousand grays from beta radiation. During this time, the esophagus had possible direct exposure to the sodium phosphate dibasic that was used as filler in the sodium iodide capsule. Because of the worsening dysphagia, an esophagogastroduodenoscopy was performed 4 weeks after the ¹³¹I therapy, which showed a new proximal esophageal stricture.ConclusionWe believe that the additional localized radiation and sodium phosphate exposure from the lodging of the ¹³¹I capsule may have contributed to the development of a proximal esophageal stricture. To our knowledge, such an occurrence has not previously been described in the medical literature. For prevention of such an occurrence, we recommend a careful swallowing evaluation of patients with any history of esophageal radiation exposure, dysphagia, or esophageal strictures before administration of ¹³¹I in capsule form. Alternative methods of ¹³¹I delivery, if available, should be considered. (Endocr Pract. 2012;18: e61-e64)     

Evaluation of 131I-Anti-Angiotensin II Type 1 Receptor Monoclonal Antibody as a Reporter for Hepatocellular Carcinoma

Background

Finding a specific agent is useful for early detection of tumor. Angiotensin II type 1 receptor (AT₁R) was reported to be elevated in a variety of tumors and participate in tumor progression. The aim of our study was to evaluate whether ¹³¹I-anti-AT₁R monoclonal antibody (mAb) is an efficient imaging reporter for the detection of hepatocellular carcinoma.

Methodology/Principal Findings

AT₁R mAb or isotype IgG was radioiodinated with ¹³¹I and the radiochemical purity and stability of the two imaging agents and the affinity of ¹³¹I-anti-AT₁R mAb against AT₁R were measured. 3.7 MBq ¹³¹I-anti-AT₁R mAb or isotype ¹³¹I-IgG was intravenously injected to mice with hepatocellular carcinoma through tail vein, and then the whole-body autoradiography and biodistribution of the two imaging agents and the pharmacokinetics of ¹³¹I-anti-AT₁R mAb were studied. ¹³¹I-anti-AT₁R mAb and ¹³¹I-IgG were successfully radioiodinated and both maintained more stable in serum than in saline. The ¹³¹I-anti-AT₁R mAb group showed much clearer whole-body images for observing hepatocellular carcinoma than the ¹³¹I-IgG group. The biodistributions of the two imaging agents suggested that hepatocellular carcinoma tissue uptook more ¹³¹I-anti-AT₁R mAb than other tissues (%ID/g = 1.82±0.40 and T/NT ratio = 7.67±0.64 at 48 h), whereas hepatocellular carcinoma tissue did not selectively uptake ¹³¹I-IgG (%ID/g = 0.42±0.06 and T/NT ratio = 1.33±0.08 at 48 h). The pharmacokinetics of ¹³¹I-anti-AT₁R mAb was in accordance with the two-compartment model, with a rapid distribution phase and a slow decline phase. These results were further verified by real-time RT-PCR, immunohistochemistry staining and Western blot.

Conclusions/Significance

¹³¹I-anti-AT₁R mAb may be a potential target for early detection of tumor.     

Intrathyroidal iodine metabolism in the rat. The influence of diet and the administration of thyroid-stimulating hormone

1. Ratios of mono[¹³¹I]iodotyrosine and di[¹³¹I]iodotyrosine (R values) and the incorporation of ¹³¹I into iodothyronines have been estimated in rat thyroid glands from 30min. to 38hr. after the administration of [¹³¹I]iodide. 2. In rats receiving a powdered low-iodine diet the R values were close to unity and did not change with time after the administration of [¹³¹I]iodide. In rats receiving a commercial pellet diet the R values fell from a mean of 0·8 at 30min. after [¹³¹I]iodide administration to 0·49 at 38hr. 3. Administration of 0·5–2·0i.u. of thyroid-stimulating hormone before giving the injection of [¹³¹I]iodide caused a small diminution in the R value when the time between injecting [¹³¹I]iodide and killing the animal was 16hr. or more. 4. Iodothyronines represented a greater percentage of the total thyroid-gland radioactivity in the iodine-deficient animals than in animals fed on the pellet diet. Thyroid-stimulating hormone had little effect, if any, on the iodothyronine contents.     

KMT2B promotes SHPRH expression to regulate 131I sensitivity in thyroid carcinoma cells by affecting FYN protein stability

Radioiodine (¹³¹I) is one of the most well-known and widely used targeted therapies. In thyroid carcinoma (THCA), it has been applied for more than eight decades and is still being utilized to eliminate remnants after resection and to reduce tumor metastases. Here, we aimed to investigate if lysine methyltransferase 2B (KMT2B) silencing could confer ¹³¹I resistance to THCA cells and the epigenetic mechanism behind. RT-qPCR, immunohistochemistry and western blot revealed that KMT2B was poorly expressed in THCA cells, and ¹³¹I resistance of cells led to a further decrease in KMT2B expression. EdU, colony formation, TUNEL, and tumor growth and metastasis assays showed that overexpression of KMT2B sensitized THCA cell to ¹³¹I and inhibited cell growth and metastasis. Further bioinformatics prediction and functional assay validation revealed that KMT2B elevated SHPRH expression via H3K4me3 modification in the SHPRH promoter, and that SHPRH modulated FYN ubiquitination, thereby promoting its protein degradation. We finally proved that the ¹³¹I-resistant cells regained resistance to ¹³¹I by FYN overexpression in the presence of KMT2B overexpression in vitro and in vivo. Therefore, we conclude that the overexpression of KMT2B represents a potential target for THCA therapy.     

Regional distribution study of brain perfusion and metabolic agents in normal and tumour bearing rat brains using autoradiographic technique

Regional distribution of brain perfusion imaging agents, [¹³¹I]N,N,N′-trimethyl-N′-[2-hydroxy-3-methyl-5-iodobenzyl]1,3 propanediamine (HIPDM) and [¹³¹I]N-isopropyl-p-iodoamphetamine (IMP), was compared with the distribution of patterns of [¹⁴C]l-methionine and [¹⁴C]d-glucose in normal and tumour bearing rat brains using autoradiographic technique. There was higher concentration of the radiopharmaceutical in grey than white matter in normal rat brain. Autoradiographs of brain tumour sections showed very low uptake of [¹³¹I]HIPDM and [¹³¹I]IMP as compared to normal brain tissue. There was moderate concentration of [¹⁴C]d-glucose and avid uptake of [¹⁴C]l-methionine in tumours. Autoradiographic study is useful for evaluating distribution patterns of radiopharmaceuticals.     

131I Induced Hematological Alterations in Rat Blood: Protection by Zinc

The present study was planned to determine the potential of zinc in attenuating the toxicity induced by ¹³¹I in rat blood. Female wistar rats were segregated into four main groups. Animals in Group I served as normal controls; Group II animals were administered a dose of 3.7 Mbq of ¹³¹I (carrier free) intraperitoneally, Group III was supplemented with Zinc in the form of ZnSo₄.7H₂O (227 mg/l drinking water), and Group IV was given a combined treatment of Zinc as well as ¹³¹I, in a similar way as was given to Groups IV and II animals, respectively. The effects of different treatments were studied on various parameters in rat blood including hemoglobin (Hb) levels, % hematocrit, zinc protoporphyrins (ZPP), activities of enzymes which included aminolevulinic acid dehydratase (δ-ALAD) and Na⁺ K⁺ ATPase and uptake of ⁶⁵Zn in blood. The study revealed an increase in the levels of hemoglobin, % hematocrit, activities of δ-ALAD, Na⁺ K⁺ ATPase and uptake of ⁶⁵Zn, 7 days after the ¹³¹I treatment. On the contrary, the levels of ZPP were found to be significantly decreased after ¹³¹I treatment. However, zinc treatment to ¹³¹I-treated animals significantly attenuated the various biochemical and hematological indices. Moreover, zinc treatment to the ¹³¹I-treated animals could significantly decrease the uptake of ⁶⁵Zn, which was increased after ¹³¹I treatment. Based upon these data, the present study suggests that zinc has the potential to attenuate ¹³¹I induced toxicity by restoring the altered hematological indices and biochemical changes.     

Effects of a high fat diet on thyroid activity,with special reference to thyroidal responses to cold

Male rats of Wistar strain were fed a standard diet (14% calories as fat or a high fait diet (80% calories as fat) for 4 to 5 weeks at 20°C. A high fat diet caused a marked hypertrophy of brown and white adipose tissue, but no change in the weight of thyroid, while there was a significant decrease in the thyroid activity as indicated by low T/S ratio. Also, the 48-hr conversion ratio of¹³¹I to protein-bound¹³¹I (PB¹³¹I) was lower. However, plasma PB¹³¹I level in this group was not different from that in the control group of rats. At 20°C plasma PB¹³¹I levels were progressively decreased over a period of 48 hours in the control group, while in the high fat diet group the initial level was maintained throughout the period. In the control group cold exposure at 3° to 5°C caused a significant elevation of PB¹³¹I level, but later it decreased to the level at 20°C. In the high fat diet group the plasma PB¹³¹I was not influenced by the same cold exposure. Fractional turnover rate of¹³¹I-thyroxine was similar in the two groups. It increased significantly on exposure to cold in the control group, while it remained unchanged in the high fat diet one. These results suggest that a high fat diet has some depressive influence on thyroidal activity and the responses to cold.

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Zusammenfassung Männliche Wistar Ratten lebten 4–5 Wochen bei 20°C und Standardfutter mit 14% Kalorien in Fett oder einem fettreichen Futter (80% Kalorien in Fett). Das fettreiche.Futter bewirkte eine starke Zunahme des braunen und weissen Fettgewebes ohne Änderung des Schilddrüsengewichtes, während die Schilddrüsenaktivität stark abfiel, erkennbar an dem niedrigen T/S Quotienten. Ebenso war die 24-Stunden Umwandlung von¹³¹I in proteingebundenes¹³¹I (PB¹³¹I) niedriger als bei den Kontroll-Tieren, jedoch war der Plasma PB¹³¹I-Spiegel der beiden Gruppen gleich. Bei 20°C fiel der PB¹³¹I-Spiegel der Kontroll-Tiere innerhalb 48 Stunden langsam ab, während er bei den fettreich gefütterten Tieren gleich blieb. In der Kontrollgruppe bewirkte 3°–5°C Kälteexponierung eine signifikante Erhöhung des PB¹³¹I Spiegels mit langsamen Abfall auf die Werte bei 20°C, während der Spiegel bei den fettreich gehaltenen Tieren unverändert blieb. Die fraktionierte Umsatzrate von¹³¹I-Thyroxin war in beiden Gruppen gleich.Sie stieg bei Kälteexponierung in der Kontrollgruppe signifikant an und blieb bei den fettreich gefütterten Tieren unverändert. Danach übt fettreiches Futter eine hemmende Wirkung auf die SD-Aktivität und Reaktionen auf Kälte aus.

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Resume On a élevé des rats mâles de la race Wistar à 20°C durant 4 à 5 semaines. Les uns recevaient une alimentation normale (14% des calories provenaient de graisses), les autres une alimentation très grasse (80% des calories étaient constitués par des corps gras). L'alimentation riche en graisses a eu pour effet une forte augmentation des tissues adipeux bruns et blancs, mais pas de modification du poids de la glande thyroïde. L'activité de celle-ci fut pourtant ralentie ce qui s'est traduit par une baisse du quotient T/S. La transformation en 24 heures de¹³¹I en iode proteïnique¹³¹I (PB¹³¹I) fut également inférieure que dans le cas des bêtes de contrôle. Pourtant, le taux de PB¹³¹I est resté le même dans le plasma des deux groupes. A 20°C, le taux de PB¹³¹I diminue lentement en 48 heures chez les bêtes de contrôle alors qu'il est resté le même chez les animaux soumis à un régime gras. Une exposition au froid (3° à 5°C) du groupe de contrôle y a provoqué une hausse significative du taux de PB¹³¹I, mais celuici redescendit au niveau antérieur, celui correspondant à 20°C. Dans le cas des rats soumis à un régime gras, on n'a pas constaté d'influence semblable lors de leur exposition au froid. Le taux fractionné de transformation de la thyroxine¹³¹I a réagi de même dans les deux groupes: Il y a ici aussi hausse significative dans le groupe de contrôle, mais pas dans celui soumis à un régime gras. Ces résultats laissent supposer, qu'un régime riche en graisses agit comme inhibiteur sur l'activité thyroïdienne et sur les réactions au froid.

     

The streptokinase–human plasminogen activator complex. Composition and identity of a subcomponent with activator activity

Reactions between purified plasminogen and streptokinase, labelled with ¹³¹I and ¹²⁵I respectively, were investigated by polyacrylamide-gel discontinuous electrophoresis. A molecular complex consisting of both ¹³¹I-labelled plasminogen and ¹²⁵I-labelled streptokinase migrated between plasminogen and streptokinase. This complex contained bovine plasminogen activator activity. The relative quantities of ¹³¹I-labelled plasminogen and ¹²⁵I-labelled streptokinase in this complex were markedly affected by reaction conditions. A fragment that retained 50% or more of the parent activator activity was released from the complex after exposure to mercaptoethanol. This subcomponent had an estimated molecular weight of 70000, and contained both ¹³¹I-labelled plasminogen and ¹²⁵I-labelled streptokinase.     

Residualizing and non-residualizing analogues of low-density lipoprotein as iodine-123 radiopharmaceuticals for imaging LDL catabolism

Low-density lipoprotein (LDL) labeled via direct iodination or via the radioiodinated residualizing moiety tyramine-cellobiose (TC) were compared in rabbits as potential ¹²³I radiopharmaceuticals for imaging sites of LDL catabolism. The tissue deposition of ¹³¹I-TC-LDL after 24 h as determined by dissection was in the major catabolic organs (liver, adrenals, spleen), and its plasma clearance was slower in rabbits with dietary hypercholesterolemia than in normals. ¹³¹I-LDL was unsuitable as a metabolic tracer due to redistribution of catabolites and/or loss of the label before protein degradation, which resulted in little accumulation of radioactivity in catabolic organs and high thyroid uptake. The plasma clearance half-time was similar (ca 22 h) for the two compounds in normal rabbits, but was increased to about 36 h for ¹³¹I-TC-LDL and decreased to approximately 9 h for ¹³¹I-LDL in hypercholesterolemic animals. The were similar with dynamic imaging of control and hypercholesterolemic rabbits using ¹²³I-labeled analogues. ¹²³I-TC-LDL rapidly localized in the liver, with low thyroid accumulation of radioactivity. The hepatic uptake of ¹²³I-LDL was about half that of ¹²³I-TC-LDL, and thyroid sequestration of radioactivity was significant for ¹²³I-LDL but not ¹²³I-TC-LDL. These data suggest that whereas the residualizing ¹²³I-TC-LDL has a pharmacokinetic profile representative of lipoprotein metabolism, the biodistribution of the activity from injected ¹²³I-LDL is complicated by processes other than protein degradation. The results are discussed with regard to nuclear medicine applications in evaluating lipoprotein catabolism in man.     

Evaluation of EGFR-targeted radioimmuno-gold-nanoparticles as a theranostic agent in a tumor animal model

This study evaluated the tumor targeting and therapeutic efficacy of a novel theranostic agent ¹³¹I-labeled immuno-gold-nanoparticle (¹³¹I-C225-AuNPs-PEG) for high epidermal growth factor receptor (EGFR)-expressed A549 human lung cancer. Confocal microscopy demonstrated the specific uptake of C225-AuNPs-PEG in A549 cells. ¹³¹I-C225-AuNPs-PEG induced a significant reduction in cell viability, which was not observed when incubated with AuNPs-PEG and C225-AuNPs-PEG. MicroSPECT/CT imaging of tumor-bearing mice after intravenous injection of ¹²³I-C225-AuNPs-PEG revealed significant radioactivity retention in tumor suggested that ¹³¹I-labeled C225-conjugated radioimmuno-gold-nanoparticles may provide a new approach of targeted imaging and therapy towards high EGFR-expressed cancers.