Ligandin binding phthalein complexone complex of technetium for hepatic function studies

In our pursuit for liver functional diagnosis, development of bifunctional radiopharmaceutical containing iminodiacetic acid (IDA), as the technetium chelating site along with phthalein or fluorescein structure, the skeleton of BSP and Rose Bengal, long used for the assessment of liver function is considered. Among the various PC, PPC, TPC and calcein IDA derivatives commercially available,^99mTc-PC (PC: 3,3-bis(N, N-dicarboxymethylaminomethyl)o-cresolphthalein) showed the highest hepatobiliary excretion. The functionality of the various technetium labeled phthalein and fluorescein IDA derivatives was evaluated by competitive BSP binding studies and by comparative binding with the hepatocyte specific protein, ligandin.     

Scintigraphic evaluation of liver transplant function

Since the initiation of liver transplantation at our institution 9 yr ago, 73 patients ranging in age from 8 mo to 64 yr have undergone this procedure. In the immediate postoperative period and at various times thereafter as deemed necessary, radionuclide studies were performed using one of the iminodiacetic acid (IDA) derivatives labeled with 99mTc. Initially, these studies were performed using labeled PIPIDA with a shift to diisopropyl IDA when this latter agent became available. The IDA agent is administered as a bolus so that the "flow" and "pooling" may be viewed immediately after injection. This is followed by sequential imaging at various times up to 24 hr, with optional graphic tracings of hepatic and bowel patterns of uptake and clearance of radioactivity. An analysis of the initial portion of the IDA scan yields useful information regarding the arterial and portal venous supply of the liver. The rapidity of hepatic concentration and excretion provides a direct measure of hepatocyte function which is particularly helpful when used sequentially to follow the response of the liver to therapy for rejection or infection. The study is also used to assess the biliary system for obstruction or leaks.     

Scintigraphic findings mimicking focal nodular hyperplasia in a case of hepatoblastoma.

Hepatoblastoma is a primary liver neoplasm in which prompt diagnosis and resection are critical to long-term survival. Liver scintigraphy using Tc-99m sulfur colloid and Tc-99m iminodiacetic acid (IDA) derivatives has been used in the evaluation of hepatic masses. Most space-occupying lesions of the liver appear as photopenic regions following either Tc-99m SC or IDA agents. Two exceptions have been reported. Focal nodular hyperplasia (FNH) has been shown to have variable colloid uptake, which is dependent upon the number of Kupffer cells per given volume. Many patients with FNH will demonstrate activity within the FNH to be greater or equal to the normal liver. In addition, two cases of hepatoblastoma have been reported to show colloid activity within the tumor, and in one patient slight uptake of Tc-99m IDA was noted in the tumor 15 minutes postinjection. The current case demonstrates a hepatoblastoma in which the scintigraphic findings with Tc-99m SC and Tc-99m IDA were similar to those reported, with retention of IDA far greater than the previously reported case.     

Evaluation of six new 99mTc-IDA agents for hepatobiliary imaging

IDA derivatives of three substituted benzothiazol, and two substituted chlorophenyl and one substituted pyrazoline compounds have been labeled with 99mTc and screened with four rat models with hepatocellular dysfunction manifesting varying degrees of change of liver architecture and hepatocellular damage associated with an active parenchymal destruction, fatty metamorphosis and cirrhosis. Organ distribution studies at 1 h postinjection have been compared in normal and diseased animal models for each agent labeled with 99mTc and with 99mTc-Disofenin (Disida) and Lidofenin (Hida) and 131I-Rose Bengal. From the data obtained with the six new IDA derivatives, the distribution kinetics of 99mTc-Arclophenin, (N-N'-2-benzoyl-4-chlorophenyl)carbamoylmethyl) imino diacetic acid (Phenida), are closely comparable to 99mTc-Disofenin in all animal models. Crossover patient studies (n = 14) for clinical evaluation of 99mTc-Arclophenin vs 99mTc-Disofenin indicate the close similarity of the 2 agents with regard to blood pool retention, gross liver/heart ratios and liver washout, suggesting Arclofenin as a suitable agent for hepatobiliary function studies. The impaired hepatocellular animal models presented should serve for fast screening of hepatobiliary agents and enable comparison of a series of closely related compounds.     

Technetium coordination state as a factor of stability in 99mTc-complexes used in hepatobiliary system: Comparative studies on 99mTc-complexes of pyridoxal with glutamate (Tc-PG) and isoleucine (Tc-PI)

Studies on ^99mTc-Penicillamine (Tc-Pen) have given us some insight into the significance of the technetium coordination state in hepatobiliary clearance behavior.A ^99mTc-complex of pyridoxal and glutamate (Tc-PG) prepared by Baker et al. (1975) using an autoclaving process or by a Sn-Resin kit method (Horiuchi 1981) was compared with a ^99mTc-complex of pyridoxal and isoleucine (Tc-PI) prepared by the method of Kato and Hazue (1978) through an intermediate compound of stannous ion, at room temperature.Tc-PG and TcPI complexes analyzed by thin layer chromatography, sephadex column chromatography (G-15), octanol extraction, and ligand exchange reaction showed different chemical properties. Their biological evaluation also demonstrated great differences in biodistribution in mice, metabolic studies, protein binding, and rat bile excretion.Tc-PG was estimated as an hepatobiliary agent with strong metal-ligand binding, inert to ligand exchange reaction with Pen at physiological pH; the likely occurrence of technetium in a mononuclear or dinuclear state providing the great stability observed in its biological and in vivo behavior was compared with the relatively weaker binding observed in Tc-PI, a highly lipophilic complex of high liver partition but of low stability, denoting its different chemical characteristics.The technetium coordination state in radiopharmaceuticals is responsible for the integrity of the molecule while in the blood pool and its relevance in impaired liver uptake is discussed.     

Radionuclide evaluation of liver transplants

Orthotopic liver transplantation is now an established technique for treating patients with various forms of end stage liver disease. The number of centers performing the procedure is increasing and, as the number of transplant recipients in the population increases, many institutions performing nuclear medicine studies will be confronted with requests to evaluate these patients. While a variety of radionuclides are proving useful in this evaluation, the 99mTc iminodiacetic acid (IDA) compounds, particularly 99mTc diisopropyl IDA (DISIDA), will probably account for the majority of radionuclide evaluations of these patients because they are well suited to monitor both structural and functional changes of the graft. The primary application of radionuclide studies is focused in the postoperative period, when problems with the vascular and biliary anastomoses, rejection, infections, and bile leaks all produce alterations in radionuclide hepatobiliary studies. Abnormalities such as rejection and infection produce primarily functional, rather than structural changes and are not easily differentiated based upon the kinetics of 99mTc-DISIDA extraction and excretion by the liver, serial imaging and correlation with clinical data is necessary in such situations. Quantitative analyses of kinetic 99mTc IDA (DISIDA) studies and quantitative approaches with other compounds such as 99mTc galactosyl-neoglycoalbumin (NGA) may permit better assessments of relatively subtle changes in liver function in the posttransplant period.     

缺铁性贫血和运动负荷对大鼠红细胞损伤的影响

本研究采用红细胞最大和平均变形性、面积、直径、膜带－３蛋白、血液和肝线粒体丙二醛、超氧化物歧化酶等指标，观察运动负荷或缺铁贫血单一因素和这两种因素同时存在对大鼠红细胞损伤的影响及其与自由基代谢的关系。结果：１．铁缺乏和运动负荷在第五周时直至实验结束均会使鼠体重增长率抑制，以缺铁贫血的运动鼠的抑制最严重。２．缺铁性贫血和运动负荷的初期、大鼠血红蛋白（Ｈｂ）和红细胞压积容量（ＨＣＴ）水平显著降低，但运动鼠在铁营养正常时，Ｈｂ及ＨＣＴ水平不再进一步降低；而运动鼠缺铁时、即使是轻度缺铁，其Ｈｂ和ＨＣＴ水平进一步显著降低。３．红细胞面积、周长、直径和球径仅在铁缺乏情况下缩小；红细胞形状因素的改变发生于缺铁性贫血的运动鼠。４．红细胞最大变形指数（ＤＩｍａｘ％）和平均变形指数（ＤＩ－ｒ％）在缺铁、运动以及缺铁贫血运动时降低，并有明显的梯度反应。静态和铁营养正常鼠的ＤＩｍａｘ％为７３．０±１．６９％，静态缺铁和运动缺铁性贫血鼠分别为６５．８±４．５７％和５８．５±６．２０％，而铁营养正常的运动鼠和轻度缺铁性贫血运动鼠分别是６９．２±１．４９％和６３．０±６．７９％，各组数据均有显著差别。三组运动鼠不论其铁营养正常与否，红细?     

Comparison of two different biliary agents in healthy subjects and in patients with liver disease

The kinetics of the iminodiacetic acids, dimethyl and diethyl IDA were studied in patients without and with liver disease. Diethyl IDA seems to be superior to dimethyl IDA in its diagnostic usefulness. It shows lower urinary excretion and a faster liver uptake, leading to more pronounced differences in liver peak time and in liver elimination half time and to faster visualisation of the gall bladder in patients with liver disease. The enterohepatic reabsorption is negligible as shown by enteral administration of the radiopharmaceutical and monitoring blood activity. Therefore it is not necessary to correct time activity curves of the liver for the IDA secreted into the gastrointestinal system. The most valuable diagnostic information with this substances may be gained in investigations on cholecystectomized patients with cholestasis.     

Comparison of two different biliary agents in healthy subjects and in patients with liver disease

The kinetics of the iminodiacetic acids, dimethyl and diethyl IDA were studied in patients without and with liver disease. Diethyl IDA seems to be superior to dimethyl IDA in its diagnostic usefulness. It shows lower urinary excretion and a faster live uptake, leading to more pronounced differences in live peak time and in liver elimination half time and to faster visualisation of the gall bladder in patients with liver disease. The enterohepatic reabsorption is negligible as shown by enteral administration of the radiopharmaceutical and monitoring blood activity. Therefore it is not necessary to correct time activity curves of the liver for the IDA secreted into the gastrointestinal system. The most valuable diagnostic information with this substances may be gained in investigations on cholecystectomized patients with cholestasis.     

Myocardial infarct imaging agents. III. Synthesis and evaluation of [203Hg] hydroxymercuriphthaleins.

Four Hg-203-mercurated phthaleins were prepared, purified, and compared with [203Hg] mercuric nitrate, [3H] phenolphthalein [203Hg] hydroxymercurifluorescein and Tc-99m-pyrophosphate in a rat model of myocardial necrosis to determine their specificities for damaged myocardium. The ratios of damaged myocardium to normal myocardium, and to blood, for the [203Hg] hydroxymercuriphthaleins (20.7-34.1 and 12.1-20.1, respectively) were somewhat lower than those reported previously for [203Hg] hydroxymercurifluorescein, but were higher than those found with [203Hg] mercuric nitrate, [3H] phenolphthalein, and Tc-99m pyrophosphate. Both the hydroxymercuri- functional group and the phthalein moiety are required for selectivity. The removal of the oxygen bridge present in fluorescein, and the replacement of carboxylic acid by sulfonic acid, had no significant effects on the sequestration process in damaged tissue.     

Detection of endotoxins in radiopharmaceutical preparations--III. Limulus test assessment using radiopharmaceutical preparations; correlation with the rabbit pyrogen test

Experiments using 17 radiopharmaceuticals containing known amounts of added endotoxin show that none of them inhibits the pyrogenic reaction of the rabbit. Gelation of the Limulus amoebocyte lysate (LAL) is inhibited by 4 of them: colloidal erbium 169Er citrate, colloidal rhenium 186Re sulfide, colloidal technetium 99mTc (Re) sulfide for liver scintigraphy and the colloidal technetium 99mTc (Re) sulfide for lymphography. This inhibition is cancelled, either by dilution or after neutral pH adjustment. Both controls were performed on 313 batches of various radiopharmaceuticals, 95% of results were identical (93% negative, 2% positive). The remaining 5% correspond to positive LAL tests vs negative rabbit tests on the same batches. No negative LAL test vs positive rabbit test was observed.     

Mechanistic aspects of the interaction of 99mTc in association with stannous pyrophosphate with damaged red blood cells

The binding of the various components of [99mTc] stannous pyrophosphate and stannous pyrophosphate/pertechnetate to damaged red blood cells is studied. It is shown that the pyrophosphate molecule enters the damaged red blood cells when the pyrophosphate concentration in blood is greater than 100 nmol/ml but does so as the uncomplexed ion. Uptake of 99mTc when introduced as [99mTc]stannous pyrophosphate is constant at approximately 18%. If the 99mTc is introduced as pertechnetate after the damaged cells are mixed with stannous pyrophosphate then at low stannous ion concentrations the uptake is directly dependent on the stannous ion concentration. However, at higher stannous ion concentrations the uptake of technetium by the damaged red cells decreases, but this decrease appears to result from several independent aspects of the sample, such as the binding of the technetium to the plasma proteins and the displacement of the technetium by pyrophosphate within the damaged cell.     

Analysis of one thousand liver scans carried out using technetium phytate (author's transl)

One thousand liver scans were carried out using technetium phytate. This soluble compound is transformed in the circulating blood into a colloid by chelation of serum calcium, thereby forming a macromolecular phytate of calcium and technetium. The presenting symptoms are compared with the isotopic findings. This microcolloid has the advantages common to all technetium tracers and, in addition, is easy to prepare and has the advantage of a distribution between the liver, spleen and bone of the same type as that seen with colloidal gold 198 without the dosimetric problems associated with the latter. Although it has a level of hepatic fixation which is less than that of certain sulphide complexes of technetium, the authors feel that it appears to provide a better relfection of the colloidopexic function of the liver.     

The effect of lipophilicity on the hepatobiliary properties of iminodiacetic acid derivatives in the conditions of hyperbilirubinemia

The partition coefficients (log P) of theoretically possible alkyliodinated iminodiacetic acid (IDA) derivatives and commercial IDA derivatives were calculated using two computer programs: ChemSketch Log P and ChemOffice Ultra. Newly synthesized ligands (DIETHYLIODIDA and DIISOPROPYLIODIDA) with the highest calculated log P were labeled with technetium-99m. The biodistribution and the influence of bilirubin on their biokinetics were investigated in rats and compared to corresponding results for commercial ^99mTc-BROMIDA. Log P of ^99mTc-complexes of synthesized ligands were determined experimentally as well as the protein binding. In comparison to ^99mTc-BROMIDA, ^99mTc-DIETHYLIODIDA has: (a) better biliary excretion (2.76±0.15%ID/g versus 1.83±0.10%ID/g); (b) faster hepatic clearance (2.90±0.21%ID/g versus 7.47±0.70%ID/g) and decreased biliary excretion (for 14% versus 22%) in conditions of hyperbilirubinemia after 15 min. It is proved that ^99mTc-DIISOPROPYLIODIDA has a prolonged hepatic transit time and decreased biliary excretion.     

Penetration of subarachnoid contrast medium into rabbit spinal cord. Comparison between metrizamide and iohexol

The penetration into rabbit spinal cord of two nonionic contrast media, iohexol and metrizamide, and a reference tracer, technetium DTPA, were compared. The spinal subarachnoid space was perfused for 4 hours with a CSF solution to which technetium DTPA and either iohexol or metrizamide had been added. The contrast media and technetium DTPA concentrations reached a plateau level in CSF outflow within 80 minutes. The contrast media concentrations in CSF were higher than the technetium DTPA (P less than .001). In the cord tissue, technetium DTPA reached higher concentrations than the contrast media (P less than .001), and iohexol reached higher concentrations relative to technetium DTPA than metrizamide (P less than .001). The mean contrast media distribution volumes in the thoracic cord were 13% (iohexol) and 12% (metrizamide). The smaller distribution volume observed for metrizamide could be related to the larger effective size of "associated" metrizamide molecules or an interference with diffusion perhaps related to binding to glucose carriers.     

A structure-distribution-relationship approach leading to the development of Tc-99m mebrofenin: an improved cholescintigraphic agent

Thirty-three HIDA (hepatobiliary IDA) derivatives were tested and correlations drawn between physicochemical parameters, structural effects, and in vivo characteristics. Capacity factors of the ligands on reverse-phase HPLC were used as a measure of lipophilicity, and to predict protein binding and in vivo distribution of the complexes. Fragmentary pi values were used to derive theoretical lipophilicities, which showed that ortho substituents have reduced lipophilic activity, probably because of self-shielding. Ortho substitution was found to affect hepatocellular transit times. Various combinations of substituents with the desired overall lipophilicity were tested. The best compound, Tc-3-bromo-2,4,6-trimethyl HIDA, possessed high hepatic specificity, and rapid hepatocellular transit; it was also resistant to competition for hepatobiliary excretion from bilirubin.     

Pharmacokinetics and clinical application of technetium 99m-labeled hepatobiliary agents

Hepatobiliary imaging, introduced first in late 1950s with iodine 131 rose bengal, has undergone major changes since the introduction of technetium 99m-labeled agents in the late 1970s. 99mTc-labeled iminodiacetic acid (IDA) agents, with their high hepatic uptake and fast biliary excretion, provide superior image resolution in addition to supplying simultaneous physiologic parameters quantitatively. The measurement of hepatic extraction fraction by deconvolutional analysis aids in separating hepatocyte from biliary disease. Excretion half-time calculation by nonlinear least square fit provides a quantitative method of analyzing hepatobiliary function and correlates directly with the severity of disease. The measurement of gallbladder ejection fraction, ejection rate, and common bile duct bile reflux index following cholecystokinin, enables quantification of the degree of obstruction to bile flow through the common bile duct. The combined application of morphologic and physiologic parameters enables diagnosis of various hepatobiliary disease, especially in early stages. Quantitative functional parameters not only provide criteria for diagnosis, but also assist in monitoring the therapeutic benefit from drugs and interventional techniques such as endoscopic sphincterotomy or balloon dilation of the obstruction. Biliary dynamic studies with cholecystokinin assist in distinguishing common bile duct dilation without obstruction from dilation with obstruction. Methods of application of 99mTc-IDA agents in quantitative physiologic studies are reviewed and future direction of their use is proposed.     

The role of IDA scintigraphy in the follow-up of liver disease in patients with cystic fibrosis

The main aim of this study was to investigate the role of N-(2,4,6 trimethyl-3-bromophenylcarbamoylmethyl) iminodiacetic acid (IDA; Mebrofenin) scintigraphy in follow-up assessments of the biliary system in patients with cystic fibrosis associated liver disease. Fourteen patients from a study published in 1996 were re-examined after a mean interval of 4.7 years from their initial study, in which diisopropylphenyl carboxymethyl iminodiacetic acid (DISIDA) was used. The results of ultrasound, liver function tests and clinical examination were also compared. Twelve of the patients had been treated with ursodeoxycholic acid and taurine in the interim. Five subjects' IDA examinations showed a slight improvement on follow-up, six deteriorated, two were unchanged, whilst one demonstrated a 'mixed picture'. Overall, nine patients deteriorated in one or more of the tests. No patient showed a decline in all four investigations and only two in three. There was poor correlation between the various follow-up examinations, with different patients showing a decline in some tests but not others. This may be due to the mixture of functional and anatomical studies utilized, their differing sensitivies, and the fact that deterioration in one did not necessarily affect another. In conclusion, follow-up of hepatobiliary disease in patients with cystic fibrosis cannot be encompassed by one method alone. If early detection of disease progression would affect management, patients will continue to require a number of investigations rather than a single test.     

The biological fate of sulphur colloid

The in-vivo behaviour of sulphur colloid has been investigated using colloids labelled with 35S as well as 99m Tc. The rates of clearance of 35S and 99m Tc from the blood, the rates of accumulation in liver and bone and the distribution of the two radioisotopes in various organs are all markedly different. The results demonstrate that although technetium is rapidly removed from the blood stream and primarily accumulated in the liver the colloid particles themselves are broken down in vivo with the release of sulphur.     

Search for 99mTc labeled DTS bifunctional radiopharmaceutical: Role of functional groups in myocardial accumulation

Development of ^99mTc-bifunctional radiopharmaceutical (BR) is attracting the interest of various research groups. In the present paper, various molecules containing a neutral ^99mTc-dithiosemicarbazone (DTS) structure as the technetium chelating site, along with various functional groups (amino, carboxyl or isobutyl group with diverse charge) are tested for their chemical or biological functions. The study on the effect of those functional groups is carried out in vitro and in vivo. The validity of introducing an amino group along with the technetium chelating site DTS for myocardial accumulation is discussed.