M. L. Gomes

Effect of an extract of cauliflower (leaf) on the labeling of blood elements with technetium-99m and on the survival of Escherichia coli AB1157 submitted to the treatment with stannous chloride

The labeling of red blood cells (RBC) with technetium-99m (99mTc) depends on a reducing agent and stannous chloride (SnCl(2)) and is widely utilized. This labeling may also be altered by drugs, and SnCl(2) reduces the survival of Escherichia coli cultures. Cauliflower (Brassica oleracea L. var. botrytis) is used in folk medicine and we evaluated its influence on (i) the labeling of blood elements with 99mTc, and (ii) on the survival of an E. coli strain. Blood was withdrawn from rats that drank the extract of cauliflower (15 days). Blood was incubated with SnCl(2) and with 99mTc, as sodium pertechnetate, centrifuged and plasma (P) and RBC were isolated. Samples of P and RBC were also precipitated, centrifuged and soluble and insoluble fractions isolated. E. coli culture was treated with SnCl(2) in the presence of cauliflower. The extract of cauliflower did not alter the fixation of 99mTc on blood fractions; however, it abolished the lethal effect of SnCl(2) on the E. coli culture. We suggest that the substances present in the extract of cauliflower probably, would have redox property with different mechanisms of action. The oxidant action of the substances of the extract would not be strong enough to oxidise the stannous ions altering the 99mTc-labeling. However, the referred substances could oxidise these ions sufficiently to protect the E. coli culture against the lethal effect of the stannous ion.

Drug interaction with radiopharmaceuticals: effect on the labeling of red blood cells with technetium-99m and on the bioavailability of radiopharmaceuticals

The evidence that natural and synthetic drugs can affect radiolabeling or bioavailability of radiopharmaceuticals in setting of nuclear medicine clinic is already known. However, this drug interaction with radiopharmaceuticals (DIR) is not completely understood. Several authors have described the effect of drugs on the labeling of blood elements with technetium-99m (99mTc) and on the biodistribution of radiopharmaceuticals. When the DIR is known, if desirable or undesirable, the natural consequence is a correct diagnosis. However, when it is unknown, it is undesirable and the consequences are the possibility of misdiagnosis and/or the repetition of the examination with an increase of radiation dose to the patient. The possible explanation to the appearance of DIR are (a) radiopharmaceutical modification, (b) alteration of the labeling efficiency of the radiopharmaceutical, (c) modification of the target, (d) modification of no target and/or the (e) alteration of the binding of the radiopharmaceutical on the blood proteins. The effect of drugs on the labeling of blood elements with 99mTc might be explained by (i) a direct inhibition (chelating action) of the stannous and pertechnetate ions, (ii) damage induced in the plasma membrane, (iii) competition of the cited ions for the same binding sites, (iv) possible generation of reactive oxygen species that could oxidize the stannous ion and/or (v) direct oxidation of the stannous ion. In conclusion, the development of biological models to study the DIR is highly relevant.

The effect of mitomycin-C on the biodistribution of 99Tcm-MDP in Balb/c mice

Drug therapy can alter the biodistribution of radiopharmaceuticals. We studied the effect of mitomycin-C, a drug used in oncology, on the biodistribution in mice of 99Tcm-methylene diphosphonic acid (99Tcm-MDP). Three doses of mitomycin-C were administered. After the last dose, 99Tcm-MDP was injected and the animals were killed. The organs were isolated, their weight determined and the percent per gram injected dose (%ID/g) calculated. The %ID/g had increased in the pancreas, ovary, stomach, uterus, kidneys, spleen, thymus, heart, liver and lungs, but did not change significantly in thyroid, bone or brain. As a change in 99Tcm-MDP uptake by bone is not observed, a modification to bone scintigraphy is not required. As mitomycin-C treatment altered 99Tcm-MDP uptake in some organs, any hot spots should be evaluated carefully to avoid a misdiagnosis.

A model to evaluate the biological effect of natural products: vincristine action on the biodistribution of radiopharmaceuticals in BALB/c female mice.

Natural products have been widely used by human beings. However, sometimes the biological effects of these products are not fully known. We are trying to develop a model to evaluate the toxicity of compounds employed as therapeutic drugs. This model is based on the capability of natural products to alter the biodistribution of radiopharmaceuticals labelled with technetium‐99m (99mTc). The acceptance of 99mTc‐labelled radiopharmaceuticals is so rapid and its current use so diverse that it is not possible to study this radionuclide’s behaviour in the body more deeply. There is evidence that the biodistribution or the pharmacokinetics of radiopharmaceuticals can be modified by some drugs, by pathological states, by irradiation and by surgical procedures. A lack of knowledge of such factors can induce a misvisualization of the scintigraphic images, leading to a misdiagnosis. Vincristine is a natural product that has been employed in various chemotherapeutic protocols in oncology. We have studied the effect of vincristine on the distribution of [99mTc]methylenediphosphonic acid ([99mTc]MDP) in female mice. After the last dose of vincristine, [99mTc]MDP was injected, the animals were sacrificed and the percentage of radioactivity (%ATI) was determined in the isolated organs. The %ATI was significantly decreased in the uterus, ovary, spleen, thymus, lymph nodes (inguinal and mesentheric), kidney, liver, pancreas, stomach, heart, brain and bone of the animals treated with the natural product. Several biological effects have been reported in patients treated with vincristine. These effects could justify the alterations in the uptake of the radiopharmaceutical in specific organs. Moreover, these results have shown that it is possible to employ this model to evaluate the toxicity of drugs. Copyright

Study of the toxicological effect of mitomycin C in mice: alteration on the biodistribution of radiopharmaceuticals used for renal eva uations

Mitomycin C (MMC) has been used as a component of many chemotherapeutic regimens and some toxic effects of this substance have been reported. As it has been reported that the toxicological effect of a drug can alter the biodistribution of radiopharmaceuticals and because patients on chemotherapeutic treatment can be submitted to a nuclear medicine procedure, we investigated whether MMC could affect the uptake of various technetium - 99m (99mTc) radiopharmaceuticals used for renal evaluations. The purpose of this study was to suggest a model to evaluate the toxic effect of substances in specific organs. Three doses of MMC (0.45 mg) were administered to mice (N= 15). One hour after the last dose, 99mTc radiopharmaceuticals, 99mTc-diethylene-triaminepentaacetic acid (99mTc-DTPA), 99mTc-dimercaptosuccinic acid (99mTc-DMSA) or 99mTc-glucoheptonic acid (99mTc-GHA), with activity of 7.4 MBq, were also administered in the treated group and in the control group (N= 15). After another 0.5 h, the animals were sacrificed. The organs were isolated, the 99mTc radiopharmaceutical uptake in the organs quantified in a well counter and the percentages of radioactivity (%ATI) calculated. The results have shown that: (i) with 99mTc-DTPA, the%ATI increased in the pancreas, ovary, uterus, stomach, kidney, spleen, thymus, heart, lung, liver, thyroid and bone; (ii) with 99mTc-DMSA, the%YATI decreased in all the organs except for the brain; and (iii) with 99mTc-GHA, the%ATI increased in the liver and decreased in the stomach, thymus, heart and thyroid. The effects of this chemotherapeutic drug on the biodistribution of these radiopharmaceuticals were statistically significant (Wilcoxon test, p<0.05) and could be explained by the metabolization and/or therapeutic action of MMC. Studies with other radiopharmaceuticals are in progress.

Assessment of the effect of vincristine on the biodistribution of 99Tcm-labelled glucoheptonic acid in female Balb/c mice.

There is evidence that the biodistribution and the pharmacokinetics of 99Tcm radiopharmaceuticals can be modified by some drugs, pathological states, irradiation and surgical procedures. Vincristine have been widely used in various chemotherapeutic protocols in oncology. We are trying to develop an animal model to assess the toxicology in different organs of compounds used as therapeutic drugs. We have studied the effect of vincristine on the distribution of 99Tcm-glucoheptonic acid (99Tcm-GHA) in female mice. After the last dose of vincristine, 99Tcm-GHA (7.4 MBq) was injected, the animals sacrificed and the percentage of radioactivity determined in the isolated organs. The percentage of activity was significantly decreased in the uterus, ovary, spleen, thymus, lymph nodes (inguinal and mesenteric), kidney and heart, but was not significantly altered in the lung, liver, pancreas, stomach, thyroid, brain and bone. Our results can be explained by the metabolic, toxic, therapeutic and immunosuppressive actions of this chemotherapeutic drug.

Model to evaluate the toxic effect of drugs : vincristine effect in the mass of organs and in the distribution of radiopharmaceuticals in mice

There are evidences that the biodistribution of radiopharmaceuticals can be modified by some drugs. As chemotherapeutic drugs present important toxic effects, we studied the vincristine effect in the mass of organs and are trying to develop a model to evaluate the action of chemotherapeutic drug using the biodistribution of radiopharmaceuticals. Vincristine was administered (n=15) into female Balb/c mice, the organs isolated and their mass determined. To study the vincristine effect in the biodistribution of technetium-99m-dimercaptosuccinic acid (99mTc-DMSA) or technetium-99m-diethylenetriaminepentaacetic acid (99mTc-DTPA), vincristine (0.03 mg) was administered in the animals (n=15) in three doses. 99mTc-DMSA or 99mTc-DTPA was injected 1h after the last dose. After 0.5h, the animals were sacrificed and the percentage of radioactivity (%ATI) and the percentage of radioactivity per gram of tissue (%ATI/g) in each organ were calculated. The results have shown that the mass decreased significantly (Wilcoxon test, P<0.05) in thymus, spleen, ovary, uterus, kidneys, pancreas. The %ATI to 99mTc-DMSA increased in lung, pancreas, heart, thyroid, brain, and bone, and the %ATI/g increased in uterus, ovary, spleen, thymus, kidney, lung, liver, pancreas, heart, thyroid, brain and bone. To 99mTc-DTPA, the %ATI increased in uterus, ovary, spleen, thymus, kidney, lung, liver, stomach, heart and bone, and the %ATI/g increased in uterus, ovary, spleen, thymus, kidney, lung, liver, stomach, heart and bone. The results were statistically significant (Wilcoxon test). The results can be explained by the metabolization, therapeutic, toxicological or immunosupressive action of the vincristine. This model, probably, should be used to evaluate the toxic effect of various drugs.

Influence of biflorin on the labelling of red blood cells, plasma protein, cell protein, and lymphocytes with technetium-99m: in vitro study

In this paper we report the results of an in vitro study involving the influence of biflorin (an o-quinone isolated from Capraria biflora L. that has potent antimicrobial activity) on the Tc-99m labeling of red blood cells, plasma protein, cells protein, and lymphocytes. Blood was withdrawn from Wistar rats and incubated with various concentrations of biflorin, and solutions of stannous chloride and Tc-99m were added. Plasma (P) and red blood cells (RBC) were isolated, precipitated, and centrifuged, and soluble (SF) and insoluble (IF) fractions were isolated. The results show that the highest concentration (100%) of biflorin is able to reduce the uptake of Tc-99m (%ATI) on RBC and the fixation on IF-P. To study the influence of biflorin on 99mTc lymphocyte labeling, human blood was submitted to a technique with Ficoll-Hypac and centrifuged, and white cells were isolated. Lymphocytes (2.5 mL; 1.0 x 106 cells/mL) were obtained and a 0.2 mL solution was incubated with biflorin (0.1 mL). Solutions of stannous chloride and 99mTc were added. Lymphocytes were separated and the %ATI bound in these cells was evaluated. A reduction in %ATI (from 97.85 ± 0.99 to 88.86 ± 5) was observed for RBC and for IF-P (73.24 ± 5.51 to 20.72 ± 6.95). In this case the results showed no decrease in %ATI for the lymphocytes with biflorin.

Assessment of a fruit extract (Sechium edule) on the labeling of blood elements with technetium-99m

Natural products have been widely used by human beings. However, sometimes the biological effects of these products are not fully known. Chayotte ( Sechium edule ) is a vegetable used in the folk medicine. Red blood cells (RBC) labeled with technetium-99m (99mTc) have several clinical applications. The aim of this work was to evaluate the influence of an extract of chayotte on the labeling of blood elements with 99mTc using stannous chloride (SnCl 2 ) in the concentrations like to 1.2, 0.006, 0.0005 and 0.0006 μg/ml. The extract of chayote was incubated in various concentrations for 1hour with blood which was withdrawn from Wistar rats. After that SnCl 2 was added and the incubation continued for more 1 h. Elapsed this time 99mTc as sodium pertechnetate (NaTcO 4 ) was toted. The blood was centrifuged and plasma (P) and RBC were isolated, also precipitated with trichloroacetic acid (TCA, 5%) and soluble (S) and insoluble (I) fractions (F) of plasma and cells (C) were determined. The radioactivity (ATI%) was rated in RBC, IF-P and IF-C. The results have showed that extract was able to reduce the radiolabeling using SnCl 2 (0.006, 0.0005 and 0.0006μg/ml). We can speculate that this effect may be on account of the products with oxidant proprieties. Key Words: chayote, red blood cells, plasma proteins, technetium-99m, radiopharmacy. African Journal of Biotechnology Vol.3(9) 2004: 484-488

Study of the binding of99mtechnetium-radiopharmaceuticals on blood cells and plasma proteins: evaluation using precipitation with trichloroacetic acid

Nuclear medicine uses radioactive tracers called radiopharmaceuticals to study the bloodflow, metabolism and morphology of an organ. Sodium pertechnetate (99mTcO4Na) and many 99mTc products are the most frequently radiopharmaceuticals used in nuclear medicine. Secure determination of the binding of 99mTc-radiopharmaceuticals to plasma (P) and blood cell (BC) constituents can help to understand the biodistribution of radiopharmaceuticals. The reported evaluations about the binding of radiopharmaceuticals on blood elements have shown that the results can not be easily compared. We decided to determine the gold standard concentration of trichloroacetic acid (TCA) to study the binding of radiopharmaceuticals on blood proteins: 99mTc-stannous colloid (99mTc-Sn-Colloid), sodium pertechnetate (99mTcO4Na), methylenediphosphonic acid (99mTc-MDP) and diisopropyliminodiacetic acid (99mTc-DISIDA). Blood of Wistar rats, was incubated with the radiopharmaceuticals for 5 minutes at room temperature, centrifuged and plasma (P) and blood cells (BC) were isolated. Samples of P and BC were also precipitated with TCA concentrations (0.1, 0.5, 1.0, 5.0, 10.0 and 20.0%) and soluble (SF) and insoluble fractions (IF) were isolated and counted. The percent radioactivity (%ATI) in IF-P depends on TCA concentration. It varies from 23.7 to 75.7 (99mTc-Sn-Colloid), from 7.8 to 26.2 (99mTcO4Na), from 10.7 to 40.4 (99mTc-MDP), from 52.2 to 60.7 (99mTc-DISIDA). The gold concentrations of TCA to study the binding of the studied radiopharmaceuticals in blood elements were revealed from the obtained results: (i) for 99mTc-Sn-Colloid in the IF-P is shown that there is no differences in the percent of radioactivity when TCA concentrations of 20 to 5.0 percent were used for precipitation, (ii) for 99mTcO4Na, 0.5 percent TCA concentration is the best one to precipitate the bound radiopharmaceutical, (iii) for 99mTc-MDP the % ATI increased from 10.7 to 40.4 with TCA concentrations from 0.1 to 5.0 percent and decreased from 40.4 to 23.8 with TCA concentrations from 5.0 to 20.0 percent and (iv) for 99mTc-DISIDA, the values of bound radioactivity are not dependent on TCA concentration in the range of 0.1 to 5.0 percent. The %ATI in IF-BC depends on TCA concentration and it varied for 99mTcO4Na (28.8 to 77.9), for 99mTc-MDP (68.8 to 83.7), for 99mTc-DISIDA (69.3 to 92.8). However, for 99mTc-Sn-Colloid, the %ATI in the insoluble fraction seems to be independent of the TCA concentration. The analysis of these results will contribute to understand the involved mechanisms on the binding of radiopharmaceuticals on blood elements. Copyright