Mitochondrial Calcium during Liver Carcinogenesis due to Thioacetamide and 4 - Dimethylaminoazobenzene

In a series of experiments the prolonged feeding of rats with thioacetamide and 4-dimethylaminoazobenzene provoked an increase in mitochondrial calcium. It seems likely that this continuous mitochondrial overloading with Ca2+ is related to metabolic and functional changes of the liver cell leading to a neoplastic transformation. The drastic changes in cell membrane permeability of cholangiocarcinoma tumor cells, reflected by an increased concentration of extracellular cations (calcium and sodium), while the intracellular cations tended to decrease, indicate that the mitochondrial function of specification of cell membrane characteristics is possibly impaired by that calcification.

Effects of Tumor Necrosis Factor on Tumor Cell Plasma Membrane Permeability

Ehrlich ascites tumor cells incubated with rabbit tumor necrosis factor (TNF)-serum showed a temperature-dependent functional impairment of the plasma membrane as reflected by permeability changes. Trypan blue inclusion and Ca2+-transport were considerably increased at hyperthermia temperature. This characteristic of the TNF-plasma membrane interaction may explain the cytotoxicity of TNF.

The Role of the Interaction between Fe(III) and Cell Surface in the Accumulation of 67Ga by Tumor Cells

The study of the interaction between complexed iron and tumor cells in the presence of 67Ga-citrate indicates that a phenomenon of iron-binding related to the thermodynamic constant of stability of the iron complex, and a hydrolysis (or anion penetration) of the interaction product determine the uptake of 67Ga. The effects of various parameters such as ionic composition of the medium, nature of the iron complex, time of incubation and number of cells are discussed.

On the Role of Tumor Cell Surface in the Accumulation of Radioisotopes

The effects of electrical charge and structural modifications of the ascites tumor cell surface on the uptake of several radiocompounds have been investigated. Changes in its electrical surface charge provoke variations in the radioactivity incorporation which appear to be selective for chelated or ionic radioisotopes. The release of a part of the cell “coat” by EDTA affects profoundly the incorporation of radioisotopes in a process which seems to be related to cell membrane permeability changes. The relationships between cell surface changes and radiocompounds accumulation are discussed.

57Co-Hematoporphyrin Accumulation by Experimental Tumors

The in vivo distribution of 57Co-hematoporphyrin in adenocarcinoma BW10232-bearing mice has been studied. Tumor-bearing and normal animals exhibit similar patterns of radioactivity accumulation. Twenty-four hours after the administration of the radiocompound the ratios tumor to blood and tumor to muscle indicate a potential value of this radioactive porphyrin for the detection of some types of tumor.

Ionic Competition and 67Ga in Vivo Accumulation

Es wurde die Wirkung verschiedener Zitrate trivalenter Kationen auf die 67Ga-Zitrat-Speicherung von Tumortieren untersucht. Eine Beziehung zwischen der Ionengröße des gleichzeitig injizierten Kations und der Hemmung der 67Ga-Speicherung weist darauf hin, daß die Eigenschaften des Kations (Ionenradius und elektrische Ladung) die wichtigste Rolle in der Speicherung der Radioaktivität spielen. Die offenbare Übereinstimmung dieses Phänomens mit der Hypothese des isomorphen Ersatzes wird diskutiert.

Radiofrequency-induced carcinogenesis: cellular calcium homeostasis changes as a triggering factor

The aim was to study the effects of radiofrequency (Rf) in a mice strain characterized by age-determined carcinogenesis of lymphatic tissues. Mice were treated with a 1?h/week Rf exposure for 4 months. A group submitted to sham exposure was used as control animals. The evolution of carcinogenesis was followed up to 18 months. The maximal life span of control mice was about 24 months. All dead animals were clinically and histologically examined to give an age-determined comparative quantification of the evolving carcinogenesis. A radiocalcium tracer method permitted the evaluation of Rf effects on transmembrane transport of extracellular calcium at 1 and 24 h after exposure. The determination of induced lipid peroxidation completed this second study. The findings show that Rf provoked an earlier general lymphocyte cell infiltration, formation of lymphoblastic ascites and extranodal tumours of different histological types, as well as an increased early mortality. The results suggest that in Rf-exposed mice, carcinogenesis may be induced earlier and with different pathological forms than in control animals. The modifications in cellular calcium homeostasis and the age-determined thymus involution appear to be important factors involved in this carcinogenesis process.

Role of iron in lymphoma-induction by ATP

Iron complexed by ATP induces lymphomas in mouse organs other than the specific targets of the lympho-adenitis provoked by sodium ATP: lymph nodes, spleen and liver. The reduction of life spans and the production of substantial volumes of ascites, that are lacking in the case of sodium ATP, are an index of the degree of malignancy of the induced lymphomas. On the basis of the known characteristics of iron-ATP complex of cellular calcium homeostasis alteration, the mechanism of these phenomena is discussed.

Iron- and aluminum-induced carcinogenesis

Ferric and aluminum complexes with ATP have shown the induction of tumors in the site of subcutaneous injection, whereas sodium ATP has not. A concomitant but apparently independent phenomenon was a severe lymphoadenitis. The tumor calcium concentration showed an inverse relationship with the tumor growth rate. Carcinogenesis and lymphoadenitis are discussed considering well known effects of ferric and aluminum complexes with ATP on the cellular calcium homeostasis and of ATP on lymphatic tissue proliferation.

Natural polyphenols-iron interaction: its biological importance

The iron-binding capacity of different fractions of natural polyphenols extracts was determined by chromatographic and electrophoretic methods. Their effects on iron-induced calcium homeostasis changes in liver tissue suspension showed that mate tea and green tea extracts provoke a very significant inhibition of the iron effects, whereas it is much less significant with red wine extract. The biological importance of this phenomenon is discussed.

Iron-ethanol synergism and pathological liver transformation

The synergistic effects of iron overload and ethanol on the liver of mice were studied over a period of 46 weeks. The determination of several parameters (iron, calcium, magnesium, alpha-hydroxyproline, lipid peroxidation, hepatomegalic and splenomegalic indexes) showed that ferrous and ferric lactates provoke an increase of calcium in the liver, higher than that of ethanol in the control animals. The relationship between liver calcium homeostasis modification and the increase of collagen and lipid peroxidation is discussed. Histological examinations showed differences in the tissular characteristics especially when iron and ethanol were given together. These findings suggest the liver calcium homeostasis changes found as a synergistic effect in the early stages of chronic iron overload may be of importance as a trigger of events leading to the pathway of fibrosis-->cirrhosis-->hepatocarcinoma reported in pathologies such as nutritional siderosis and hemochromatosis.

Effects of low-molecular-weight aluminum complexes on brain tissue calcium homeostasis

The in vitro effects of low-molecular-weight aluminum complexes (citrate, lactate, and ATP complex) on the Ca2+ uptake and aluminum-induced lipid peroxidation of brain tissue show that the modification of the calcium homeostasis is determined by the nature of the ligand and that there is no correlation between the aluminum-induced lipid peroxidation and the Ca2+ uptake. The same characteristics have been shown by a similar study performed with Ehrlich carcinoma cells. The electrophoretic analyses of the aluminum lactate-albumin and aluminum lactate-ATP interactions indicate an aluminum transfer from the lactate to the albumin and ATP ligands. The increased Ca2+ uptake when ATP is present in the incubation medium with aluminum citrate and aluminum lactate corroborates the suggested mediator role of ATP in cellular calcium homeostasis modification induced by iron.

ATP in iron overload-induced intracellular calcium changes

The cellular iron uptake from low molecular weight iron complexes (ferric citrate, ferric lactate and ferric ATP complex) is concentration-dependent, and only a small part of the iron penetrates the cell as shown by deferoxamine treatment. A threshold of iron concentration in the cell must be reached for the iron complex-induced increase of cellular Ca2+-uptake. ATP seems to play a key role in an iron translocation that enhances the effects of the iron complexes. A non-specific and competitive iron-binding by proteins seems to act as a buffer system that reduces the iron overload effects. Calcium channel blockers have no effects on the iron complex-cell interaction or iron-induced Ca2+-uptake modification. An iron complex concentration-dependent inhibition of the CaATPase activity, and its consequent Ca2+-extrusion impairment appear as the likely cause of calcium overload. The relevance of these findings in iron overload-induced pathologies is discussed.

ATP in cellular calcium-overload by trivalent metal ions

Extracellular Ca2+-influx induced by trivalent metal ions (Fe3+, Al3+, Cr3+, In3+, Ga3+, and La3+) in Ehrlich carcinoma cells is enhanced by ATP. This action seems to be related to the high coordination capacity of the ATP ligand that inhibits the polymerization of the solvated cations taking place at physiological pH, and consequently permits their biological activity. A general relationship between induced lipid peroxidation and increased calcium uptake was not found. These results emphasize the ATP role in the toxicity of trivalent metals, and its possible involvement, via cellular calcium overload, in a neurodegenerative process, such as Alzheimer's and Parkinson's diseases, in whose etiology the implication of aluminum and iron has been suggested.

Non-transferrin-bound iron and tumor cells

The study of iron uptake from low molecular weight complexes by Ehrlich carcinoma cells shows concentration-dependence, and ATP increases the iron uptake from citrate and lactate complexes. Blood proteins can act as inhibitors, and deferoxamine chelation of cell-bound iron complex indicates that the percentage of iron penetrating the cell is about the same for a wide range of iron complex concentrations in the incubation medium (about 5% for ferric lactate). Ascorbic acid increases iron uptake and simultaneously decreases lipid peroxidation. Electrophoresis shows a very high iron transfer from ferric lactate to ATP, and to a lesser extent to ADP and AMP. In the pathological evolution of iron overload to a neoplasia, the probable involvement of an iron exchange between iron complexes from non-transferrin-bound iron of plasma and ATP is discussed.

Effects of iron complexes on brain calcium homeostasis

The effects of two physiological low molecular weight iron complexes, ferric lactate and ferric adenosine triphosphate (ATP) on brain Ca2+ homeostasis modification, have been studied in vitro and in vivo. In vitro ferric ATP complex shows a higher efficiency as modifier of Ca2+ homeostasis. This higher reactivity and the in vivo observed effect of increased brain uptake of iron from ferric lactate provoked by the presence of ATP, corroborate in vitro results showing an iron transfer from ferric lactate to ATP, as well as the mediator role of ATP in the iron-induced cellular Ca2+ homeostasis modification process. The possible role of this process in Parkinson's disease is discussed.

Role of lipid peroxidation in iron-induced cellular calcium overload

Calcium overload is the common pathway leading to cell injury. The role of iron-induced lipid peroxidation in the modification of Ehrlich carcinoma cells calcium homeostasis has been studied. There is a lack of correlation between that modification and the value of lipid peroxidation. The stability characteristics of low-mol-weight iron complexes affect lipid peroxidation and, to a lesser extent, cellular calcium uptake. Lipid peroxidation appears not as a triggering factor of cellular calcium homeostasis modification, but as a concomitant phenomenon.

Iron, intracellular calcium ion, lipid peroxidation and carcino-genesis

The evaluation of the accumulated experimental results on the action of complexed iron on cells indicates that the provoked cell injury is rather the consequence of an inhibition of the cytosolic Ca2+ concentration regulatory system than an effect of iron-induced lipid peroxidation. The role of the consequent intracellular ionic environment change in the preneoplastic and neoplastic transformation of the cell is discussed.

Cardiotoxicity of parenterally administered iron complexes

The role of cell calcium overload in the cardiotoxicity of low molecular weight iron complexes has been studied using 45Ca(2+)-uptake determinations in mice intraperitoneally injected with ferric lactate and ferric-ATP complex. Heart tissue shows a very high increase of 45Ca(2+)-uptake which appears to corroborate the hypothesis of cardiotoxicity by calcium overload. ATP seems to play a role in the degree of iron complex efficiency as cell calcium homeostasis modifier.

The role of ATP as a mediator in the action of iron complexes on cellular calcium homeostasis

The effects of the interaction between low molecular weight iron complexes (citrate, lactate, and ATP complexes) with ATP and proteins, on the modification of Ehrlich carcinoma cell calcium homeostasis have been studied. In that modification the ferric-ATP complex shows much higher activity than the others. Sodium ATP, by iron translocation from citrate and lactate, increases their activity. This phenomenon implicates ATP as a mediator on the cellular activity of the complexes. Proteins, particularly ferritin, appear to moderately reduce their activity, whereas glutathione and ascorbic acid, acting as lipid peroxidation-inhibitors, show only a slight reduction of the iron complex's effects on cellular calcium uptake.

Iron chelation and tumor cell calcium homeostasis

The effects of iron chelation on calcium homeostasis of Ehrlich carcinoma cells were studied using 59Fe-ferric lactate and 45CaCl2. Desferrioxamine action on bound iron is characterized by the presence of an insoluble fraction located deep in the cell membrane and another soluble fraction on the cell surface. The competitive binding by albumin suggests that the iron is bound by protein containing molecular structures of the cell. The modification of cellular calcium homeostasis induced by ferric lactate, which is a phenomenon inherent in cell injury, is not caused by lipid peroxidation. The role of iron-induced cellular calcium homeostasis in carcinogenesis is discussed.

Modification of in vivo Ca(2+)-uptake by parenterally administered aluminum complexes

The parental administration of complexed aluminum induces a very significant increase of Ca(2+0-uptake by various tissues. The effects are more important with aluminum-ATP complex than with the simultaneous administration of aluminum lactate and sodium ATP. In the last case the increase in calcium uptake does not reach the many fold (up to 7 times) values observed with aluminum-ATP complex. In this aluminum-induced modification of cellular calcium homeostasis ATP appears to act as a mediator of the metal complex effects. These experimental results emphasize the importance of the role of ATP in the biological properties of low molecular weight metal complexes.

Long-term oral administration of aluminum in mice. Aluminum distribution in tissues and effects on calcium metabolism

Six months of oral administration of aluminum lactate provokes an important accumulation of aluminum in various tissues of mice. The accumulation magnitude order is spleen > kidney > brain > liver > blood. No systemic toxic effects (weight loss or neurolytic effects) were observed. Values of calcium content and 45Ca-uptake by the different tissues showed no modifications of calcium metabolism. The lack of calcium homeostasis modification caused by a probable aluminum insolubilization, and the incidence of other individual factors on individual deviations from group behavior is discussed.

Effects of albumin and adenosine phosphates on iron transfer from ferric lactate

Ferric lactate is known to modify Ca2+ uptake by the cells. To enlighten the role of protein and ATP in this phenomenon, iron transfer from ferric lactate to albumin and adenosine polyphosphates was determined by electrophoresis. The order of iron affinity was ATP > ADP > AMP for the polyphosphates, and albumin does not compete for iron binding with the polyphosphates. The iron transfer to ATP was also observed in vivo by adsorption chromatography of the adenosine polyphosphates fraction from blood plasma of mice injected with ferric lactate plus ATP. In vitro iron and calcium uptake by Ehrlich ascites tumor cells showed that albumin and ATP decreased iron uptake, whereas calcium incorporation is diminished by albumin but augmented by ATP. This difference might be explained by albumin binding of ferric lactate that is inhibited from reaching cell structures, whereas ATP, known to be an inhibitor of iron polymerization, facilitates it.

In vivo distribution of ferric-ATP complex

At physiological pH, ferric-ATP complex presents ionic characteristics unlike those of ferric lactate. Its rapid diffusion into the tissues, and its reactivity which is not impaired by polymerization seem responsible for its toxicity. In comparison with ferric lactate, after parenteral administration there is a much higher spleen, lung, kidney and bone accumulation. After oral administration, on the other hand, the values are lower. ATP hydrolysis by the stomach's pH, and the subsequent iron insolubilization as phosphate could be the reason for this behaviour.

On the mechanism of soft tissue calcification induced by complexed iron

The interaction of ferric lactate with Ehrlich carcinoma ascites cells induces a modification of Ca(2+)-uptake which is in direct relationship with the iron mass bound to the cells. Competitive binding of iron by deferoxamine indicates that only a part of the bound iron penetrates the cell, and that to trigger a Ca(2+)-influx this intracellular iron must be over a threshold concentration. The experimental finding that ferric lactate transfers its iron to albumin and to ATP suggests that in the Ca(2+)-uptake modification it works through its iron transfer which provokes the inhibition of the cell calcium homeostasis regulatory systems (Ca(2+)-channels, intracellular Ca(2+)-binding sites and Ca(2+)-pump ATPase). The involvement of ATP in the action of ferric lactate seems related to a higher stability of the complex, and to a larger availability of active iron able to perform the inhibitory process.

Role of lipid peroxidation in ferric lactate-enhanced calcium uptake by Ehrlich carcinoma cells

Comparison of Ca2+ uptake by Ehrlich carcinoma cells in presence of ferric lactate or aluminum lactate, and formation of thiobarbituric acid-reactive substances, suggests that lipid peroxidation is associated with but not the cause of calcium overload that can lead to cell injury and death.

Soft tissue calcification induced by iron complexes

Complexed iron (III) induces a local calcification of soft tissues in mice that is strongly dependent upon the nature of the complexing molecule. Ferric lactate is much more effective in inducing calcification than iron dextran.

Ehrlich tumour cells: Ca(2+)-uptake modification by aluminium lactate

Aluminium lactate provokes the same modification of 45Ca(2+)-uptake by Ehrlich ascites tumour cells as does ferric lactate. The increase of uptake is metal-complex concentration-dependent, and in contrast to ferric lactate, is only partially inhibited by albumin. Under the same experimental conditions, chromic lactate provoked no modification of that uptake. A plasma membrane rigidity increase provoked by coordination binding of aluminium to phospholipids is likely to be the main cause of Ca(2+)-uptake modification by aluminium lactate.

Changes in calcium uptake by liver induced by ferric lactate

In vitro and in vivo Ca(2+)-uptake by the liver is increased by ferric lactate. In vitro albumin and deferoxamine inhibit ferric lactate effects. Electrophoresis demonstrates the binding of ferric lactate to albumin. In vivo, ferric lactate induces a significant increase of Ca(2+)-uptake by liver, with a maximum of 2.9 nmol/g against 0.66 nmol/g for control livers (P less than 0.005) between 5 and 24 h after administration. This uptake modification is reversible, while the amount of iron (measured as 59Fe taken up) remains constant throughout the experiment. The affinity of ferric lactate for protein and the iron mass-dependence of Ca(2+)-uptake increase support for the hypothesis of a ferric lactate-cell membrane interaction rather than an iron-catalyzed cell injury by lipid peroxidation as the major event leading to an increased Ca(2+)-uptake.

The role of the interaction between Fe(III) and cell surface in the accumulation of 67Ga by tumor cells

The study of the interaction between complexed iron and tumor cells in the presence of 67Ga-citrate indicates that a phenomenon of iron-binding related to the thermodynamic constant of stability of the iron complex, and a hydrolysis (or anion penetration) of the interaction product determine the uptake of 67Ga. The effects of various parameters such as ionic composition of the medium, nature of the iron complex, time of incubation and number of cells are discussed.

In vivo behaviour of low molecular weight iron complexes

The in vivo distribution in mice of ferric citrate, ferric beta-glycerophosphate and ferric lactate complexes has been studied. There is a relationship between the 59Fe uptake by various tissues and the physicochemical characteristics of the complexes. Ferric lactate seems a useful preparation for iron deficiency therapy.

Effects of Fe(3+)-tumor cell interaction on Ca(2+)-uptake by Ehrlich ascites tumor cells

Fe3+ ions complexed by various ligands induce an increased Ca2+ uptake by Ehrlich carcinoma ascites cells that is proportional to the thermodynamic stability constant of the complex, and the greatest increase is observed with ferric lactate. The absence of ATPase inhibition showed by this ferric complex, suggests that an increased passive diffusion of Ca2+ due to structural modifications of the cell membrane is the most probable cause of this phenomenon.

Cell labelling with 67Ga-citrate

A method of cell labelling with carrier-free 67Ga-citrate, based on a co-binding with iron from ferric lactate has been developed. 67Ga-binding has a direct relationship with the iron incorporation by the cell. Using this method Ehrlich ascites tumor cells increase their uptake from 5% (no ferric lactate) to 89% (5 mumol of ferric lactate). Erythrocytes have shown the same pattern of 67Ga-binding. In vivo cytotoxic assays (ascites formation and animal survival) have demonstrated the lack of cytotoxicity of ferric lactate under these experimental conditions. Electrophoretic analyses of 67Ga-labelled tumor cells and erythrocytes have shown the absence of free 67Ga-citrate.

Improvement of Radioactive Colloid Binding by Tumor Cells

Treatment of P388 leukemia cells with poly-DL-lysine (Poly-lys) considerably increases the binding of colloidal chromic phosphate (32P). This augmentation of the number of particles that are bound is in direct relationship with Poly-lys concentration, and very significantly with its degree of polymerization. Treatment with Poly-lys molecular weight 77,000 shows a 100% increase of binding with 200 μg and of 50% with 100 μg. Poly-lys M.W. 8,000 presents no significant increase, and for the other molecular weights the binding is intermediate.

Effects of iron-binding proteins on in vitro uptake of 67Ga-citrate by tumor cells

A comparative study of carrier-free 67Ga-citrate uptake by Ehrlich ascites tumor cells in the presence of lactoferrin, transferrin and ferritin has demonstrated that lactoferrin considerably increases the uptake of 67Ga, and that this increase seems to be determined by its iron-load. The other iron-binding proteins assayed have a null or negative effect. Their behavior in the presence of sodium citrate supports the concept of lactoferrin-binding by the cells as responsible for the uptake. The different behavior of 67Ga-citrate iron-binding protein complexes appears to support this hypothesis.

Enhancement of colloid uptake by tumor cell surface electrical charge modification

Colloidal [51Cr]chromic phosphate uptake is considerably increased by preincubation of P388 ascites leukemia cells with poly(DL-lysine). The uptake increase is in direct relationship with the concentration and the degree of polymerization of poly(DL-lysine). The probable implication of cell surface electrical charge modification in these phenomena is discussed.

Iron-binding proteins and 67Ga accumulation by tumor cells

Tumor cells incubated with 67Ga-citrate plus lactoferrin showed a lactoferrin concentration-dependent increase of 67Ga uptake while for transferrin the effect was an inhibition. A correlation was observed between the binding of 131I-labelled lactoferrin or 131I-labelled transferrin and the uptake of 67Ga by the cells. Saturation with iron did not change significantly the effects of the iron-binding proteins. Preincubation with lactoferrin, transferrin or ferric citrate increased 67Ga uptake. The formation of a ternary complex in which 67Ga mimics iron is discussed.

Iron-Binding Proteins and 67Ga Accumulation by Tumor Cells

Tumor cells incubated with 67Ga-citrate plus lactoferrin showed a lactoferrin concentration-dependent increase of 67Ga uptake while for transferrin the effect was an inhibition. A correlation was observed between the binding of 131l-labelled lactoferrin or 131l-labelled transferrin and the uptake of 67Ga by the cells. Saturation with iron did not change significantly the effects of the ironbinding proteins. Preincubation with lactoferrin, transferrin or ferric citrate increased 67Ga uptake. The formation of a ternary complex in which 67Ga mimics iron is discussed.

In vivo changes of ionic composition of tumors treated by hyperthermia

Experimental tumors submitted in vivo to hyperthermia, in the presence, or not, of lanthanum (La3+), have shown modifications in the concentration of extra- and intracellular cations. Sacrificed immediately after hyperthermia, only the group treated with La3+ presented ionic changes (lower magnesium and potassium). After 48 hours, in both cases calcium and sodium were increased while magnesium and potassium were decreased.

On the role of transferrin in 67Ga uptake by tumor cells

In vitro uptake of 67Ga-citrate and 59Fe-citrate by DS sarcoma cells in the presence of tumor-bearing animal blood plasma showed a dramatic inhibition of both 67Ga and 59Fe uptakes: about 1/10 of 67Ga and 1/50 of the 59Fe are taken up by the cells. Subcellular fractionation appears to indicate no specific binding to cell structures, and the difference of binding seems to be related to the transferrin chelation and transmembrane transport differences.

Mechanisms of gallium-67 accumulation by tumors: role of cell membrane permeability

The effects of citrate ion on in vitro and in vivo uptake of [67Ga]citrate by tumor cells have been studied. Carrier-free [67Ga]citrate seems to follow the physical diffusion of citrate ions into the cell, and the presence of carrier gallium inhibits that diffusion, reducing considerably its uptake. These results appear to support the hypothesis that increased permeability of tumor cells is the principal cause of [67Ga]citrate accumulation by tumors.

On the Role of Transferrin in 67Ga Uptake by Tumor Cells

In vitro uptake of 67Ga-citrate and 59Fe-citrate by DS sarcoma cells in the presence of tumor-bearing animal blood plasma showed a dramatic inhibition of both 67Ga and 59Fe uptakes: about ii/io of 67Ga and 1/5o of the 59Fe are taken up by the cells. Subcellular fractionation appears to indicate no specific binding to cell structures, and the difference of binding seems to be related to the transferrin chelation and transmembrane transport differences

Antitumor activity of gallium and lanthanum: role of cation-cell membrane interaction

Using the vital dye inclusion method and the radioisotopic study of Ca2+-transport, we have investigated the involvement of the gallium and lanthanum plasma-membrane interaction in the cytotoxic and antitumor characteristics of both cations. The experimental results support the hypothesis that such an interaction is the principal cause of antitumor activity, either through structural changes of the cell membrane or through inhibition of the ATPase pumps.

Effects of hyperthermia and lanthanum on tumor cell leakage

The effects of hyperthermia temperature and the presence of lanthanum on the release of Ehrlich's ascites cell molecules labelled with radiophosphorus have been studied. The leakage of intracellular molecules is in relationship with the temperature and the time of incubation. The phenomenon presents the characteristics of an increased passive diffusion induced by a thermotropic modification of the protein-lipid environment of the plasma membrane. The possible implication of this phenomenon on hyperthermic energy depletion and enhanced cytotoxicity of chemotherapeutics with poor cell penetration is discussed.

Effects of concanavalin A on 67Ga binding by tumor cells

The in vitro uptakes of 67Ga-citrate and 45Ca-chloride in the presence of concanavalin A have shown that at low concentrations (10-50 micrograms/ml) 67Ga presents a significant increase not observed for 45Ca. At higher concentrations there is a sharp augmentation of both 67Ga and 45Ca incorporations. The augmentation of Trypan blue inclusion is a concomitant phenomenon at any concanavalin A concentration that indicates tumor cell plasma membrane changes in direct relationship with 67Ga uptake increase.

Effects of gallium chloride oral administration on transplanted C3HBA mammary adenocarcinoma: Ga, Mg, Ca and Fe concentration and anatomopathological characteristics

To determine the influence of the length of the treatment on the anatomopathological and biochemical intratumor changes induced by gallium, we treated C3H BA mammary adenocarcinoma-bearing C3H/HeJ mice with gallium chloride daily, for a period of either 21 or 42 days. In both cases the same dose of 200 mg/kg/24h was administered. An increase of collagen fibrosis in treated tumors as opposed to controls was only noted after 42 days, as well as a significant decrease of the intratumor magnesium and calcium concentrations that could be responsible for a reduction in the metabolic activities of the malignant cells. Remarkable intratumor gallium concentrations (38.4 +/- 30.3 nmol/g after 21 days of treatment; 13.4 +/- 7.3 nmol/g after 42 days where the necrosis is much more important) are obtained after this oral administration. There is no renal toxicity and a higher tumor/kidney concentration ratio is obtained than after acute parenteral administration. The effect of gallium may be different according to the mode of administration: it may be more cytotoxic after parenteral administration, while after oral administration it may act as a better metabolic regulator with a more selective tumor uptake and fewer side effects.

Experimental evidence for the probable involvement of calcium ion transport in 67Ga uptake by tumour cells

The study of 67Ga-citrate uptake and calcium transport in Ehrlich ascites tumour cells seems to indicate that their peculiar characteristic of increased permeability to extracellular calcium ion might be responsible for their 67Ga accumulation. Experiments performed under different conditions of extracellular calcium, temperature, and presence of ionophore and other plasma membrane modifying agents such as lanthanum appear to corroborate this hypothesis.

Calcium and ATPase activity during hepatic intoxication with thioacetamide

The effects of acute thioacetamide (TAA) intoxication on the calcium, magnesium, sodium and potassium content of liver and on its ATPase activities were studied in rats. Samples of liver were analyzed by atomic absorption spectrometry for their cationic content 6, 24 and 48 h after administration of TAA through a stomach tube. After sonification other samples were assayed for (Na+ + K+)-dependent, (Ca2+ + Mg2+)- and Ca2+-dependent ATPases. No apparent correlation has been found between the increased hepatic calcium after TAA treatment and the variations of ATPase activity. Both calcium movement and ATPase activity appear sex-determined. These results bring support to the hypothesis that an interaction between TAA or its metabolites with the cell membrane provokes an increased influx of extracellular calcium. The relationship between this calcium increase and the changes in ATPase activity with the events triggering the neoplastic transformation is discussed.