The in vivo effect of the administration of resistance-modulating agents on rhodamine 123 distribution in mice thymus and lymph nodes.

P-glycoprotein (Pgp) has been widely associated with the multidrug resistance phenotype. Nevertheless, this protein has been detected in many normal tissues and cells, including liver, kidney, endothelial cells that constitute the hematological barrier of the brain and testes, and cells from the immune system. Many in vitro models have been used to study drugs that modulate Pgp activity and the multidrug resistance phenomenon. In the present work, we investigate the in vivo effects of resistance-modulating agents on lymphoid organs. Rhodamine 123 (Rho123), a well-known Pgp substrate, was administered to mice, and the fluorescence level in thymus and lymph node cells measured. The fluorescence level on these organs showed a dose-dependent response. Cyclosporin A (CSA), Verapamil (VP) and Trifluoperazine (TFP), three resistance-modulating agents, were administered to mice 1 h prior to 1 mg/kg Rho123 administration. Surprisingly, VP (10 mg/kg) and TFP (750 microg/kg) did not modulate Rho123 retention by thymus and lymph node cells. CSA (50 mg/kg) was the only drug that increased the fluorescence level in both organs. These results point out to the need of a wider study on the in vivo effects of resistance-modulating agents in different organs and systems.

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.

Effect of a chemotherapeutic drug on the biodistribution of 99mTc-DTPA in Balb/c mice.

The biodistribution of radiotracers used in diagnostic imaging can be grossly and recognizably altered by a wide variety of drugs and other treatment modalities, such as surgery and radiotherapy. Knowledge of such altered biodistribution is important both in making diagnostic inferences from scans and in dosimetric considerations. Vincristine is a drug that has been used as a component of many chemotherapeutic regimens because of its relative lack of hematologic toxicity. Its mechanism of action is by interfering with microtubule formation. The metabolic fate of vincristine has not been clearly determined and apparently undergoes in vivo decomposition. We have studied the effect of vincristine on the biodistribution of the 99mTc-DTPA. Vincristine was administered by ocular plexus via into female isogenic Balb/c mice. One hour after the last dose, 99mTc-DTPA (7.4 MBq) was injected and after 0.5 hour the animals were rapidly sacrificed. The organs were isolated, the radioactivity uptakes determined in a well counter and the percentages of radioactivity (% rad) in the organs calculated. The results have shown that the percentage rad has not been significantly altered in pancreas, thyroid and brain whilst a significant increased in thymus, ovary, uterus, spleen, kidney, heart, stomach, lung, liver and bone was reported. The results could be explained by the metabolization and/or therapeutic and immunosuppressive action of vincristine.

Effect of cyclophosphamide on the binding of 99mTcO-4 and 99mTc-MDP to blood cells and plasma proteins.

Since the introduction of technetium-99m (99mTc) and its rapid acceptance as a tool in nuclear medicine, very little information is available about its biological action as 99mTc-radiopharmaceuticals. We have determined if cyclophosphamide, an alkylating agent, used in oncology as a chemotherapeutic drug, modifies the binding of 99mTcO-4 and 99mTc-MDP (99mTc-methylenediphosphonic acid) to blood cells and to plasma proteins. The radiopharmaceuticals were injected intravenously (iv) into SW-55 mice (male and female, weight 25 g) and samples of plasma and blood cells were separated. Cyclophosphamide (50 micrograms) was injected iv 1 h before the radiopharmaceuticals. Samples of plasma and blood cells were also precipitated with 5% trichloroacetic acid and soluble and insoluble fractions were isolated. The following results were obtained: 1) cyclophosphamide did not alter (0.25 to 8 h) percent radioactivity of 99mTcO-4 in plasma or blood cells but increased the binding of 99mTc-MDP to blood cells; 2) cyclophosphamide did not alter (0.25 to 8 h) the binding of 99mTcO-4 in insoluble fraction of plasma and decreased (1 to 4 h) percent radioactivity of 99mTc-MDP in the insoluble fraction of plasma; 3) cyclophosphamide increased (0.25 to 4 h) percent radioactivity of 99mTcO-4 in the insoluble fraction of blood cells but did not alter the binding of 99mTc-MDP. Cyclophosphamide and/or its metabolites modified the effective half-life of these radiopharmaceuticals (to 99mTcO-4 was increased 2.3 to 3.4 h and to 99mTc-MDP was decreased 3.3 to 2.1 h) and possibly increased the permeability of blood cells to 99mTcO-4.

In vitro effect of cyclophosphamide on the binding of radiopharmaceuticals (99mTcO4- and 99mTc-MDP) to blood elements.

Sodium pertechnetate (99mTcO4-) and many 99mTc-products are the radiopharmaceuticals most frequently used in nuclear medicine. Using an in vitro model, we evaluated the effect of cyclophosphamide on percent radioactivity of 99mTcO4- and methylenediphosphonic acid (99mTc-MDP) bound to isolated blood elements. Blood samples were incubated with the two radiopharmaceuticals, plasma and blood cells were separated and precipitated, and soluble and insoluble fractions were separated. To evaluate the effect of cyclophosphamide, blood was incubated with this drug 1 h prior to the addition of the radiopharmaceuticals. The fraction of 99mTcO4- radioactivity was slightly higher in plasma (61.2 to 53.8%) than in blood cells (38.8 to 46.2%) up to 6 h and cyclophosphamide did not interfere with this distribution. The amount of 99mTc-MDP radioactivity was higher in plasma (91.1 to 87.2%) than in blood cells (8.9 to 12.8%) up to 24 h and cyclophosphamide did not modify it. The binding of 99mTcO4- to the insoluble fraction of plasma (4.9 to 6.1%) was low and cyclophosphamide did not interfere with it up to 6 h, but a small blockade (9.8 to 4.8%) was observed at 24 h. From 3 h on, cyclophosphamide slightly inhibited 99mTcO4- binding to blood cells (23.1 to 16.6%) and increased it at 24 h (31.2 to 14.3%). Cyclophosphamide did not alter 99mTc-MDP binding to the insoluble fraction of blood cells and slightly decreased 99mTc-MDP binding to the insoluble fraction of plasma (29.8 to 23.6%) up to 6 h.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro radioautographic studies of the biodistribution of radiopharmaceuticals on blood elements.

In the present study we evaluated the binding of the radiopharmaceuticals sodium pertechnetate (Na 99mTcO4), methylenediphosphonic acid (99mTc-MDP) and glucoheptonate acid (99mTc-GHA) to blood elements using centrifugation and radioautographic techniques. Heparinized blood was incubated with the labelled compounds for 0, 1, 2, 3, 4, 6 and 24 h. Plasma (P) and blood cells (BC) were isolated and precipitated with 5% trichloroacetic acid (TCA), and soluble (SF) and insoluble fractions (IF) were separated. Blood samples were prepared (0 and 24 h) and coated with LM-1 radioautographic emulsions and percent radioactivity (%rad) in P and BC was determined. The binding of Na 99mTcO4 (%rad) to P was 61.2% (0 h) and 46.0% (24 h), and radioautography showed 63.7% (0 h) and 43.3% (24 h). The binding to BC was 38.8% (0 h) and 54.0% (24 h), and radioautography showed 36.3% (0 h) and 56.7% (24 h). 99mTc-MDP study presented 91.1% (0 h) to P and 87.2% (24 h), and radioautography showed 67.9% (0 h) and 67.4% (24 h). The binding to BC was 8.9% (0 h) and 12.8% (24 h), and radioautography showed 32.1% (0 h) and 32.6% (24 h). 99mTc-GHA study was 90.1% (0 h) to P and 79.9% (24 h), and radioautography showed 67.2% (0 h) and 60.1% (24 h). The binding to BC was 9.9% (0 h) and 20.1% (24 h), and radioautography showed 32.8% (0 h) and 39.9% (24 h). The comparison of the obtained results suggests that the binding to plasma and blood cells in the two techniques used (radioautography and centrifugation) is qualitatively in accordance.

The effect of vincristine on the biodistribution of technetium-99m DTPA, GHA, and DMSA in Balb/c female mice.

OBJECTIVE: Vincristine has been widely used in various chemotherapeutic protocols in oncology. The purpose of this study was to evaluate the effect of vincristine on the biodistribution of 99mTc-DMSA, 99mTc-GHA, and 99mTc-DTPA in Balb/c female mice. METHODS: Vincristine (0.03 mg, 0.3 mL) was injected into female isogenic Balb/c mice (n = 15), in 3 doses over an interval of 96 h. The 99mTc-DMSA, 99mTc-GHA, or 99mTc-DTPA (7.4 MBq) was administered after the last dose of vincristine. After 0.5 h the animals were killed rapidly. The organs (pancreas, thyroid, brain, thymus, ovary, uterus, spleen, kidney, heart, stomach, lung, liver, bone, and lymph nodes) were isolated and the radioactivity in each organ was counted in a NaI(Tl) well counter. The percentage of radioactivity (%) in each was calculated and compared with the control group. Statistical analysis was performed by Wilcoxon test (P < 0.05). RESULTS: The percentage of 99mTc-DMSA was increased in the lung, pancreas, heart, thyroid, brain, bone, and lymph nodes (inguinal and mesenteric). The percentage of 99mTc-GHA was decreased in the uterus, ovary, spleen, thymus, lymph nodes (inguinal and mesenteric), kidney, and heart. The percentage of 99mTc-DTPAwas increased in thymus, lymph nodes (inguinal and mesenteric), ovary, uterus, spleen, kidney, heart, stomach, lung, liver, and bone. CONCLUSION: The results could be explained by the metabolization, toxic effect, therapeutic, or immunosupressive action of the studied chemotherapeutic drug.

Consumo alimentar residual e sua relação com medidas de desempenho e eficiência e características in vivo da carcaça de cordeiros / The residual feed intake and its relationship with performance and efficiency measures and in vivo carcass characteristics of lambs

Avaliou-se o consumo alimentar residual (CAR) e a conversão alimentar (CA) de 20 cordeiros, com o objetivo de estimar as correlações entre essas variáveis com medidas de desempenho e com características in vivo da carcaça. Os animais tiveram o consumo de MS (CMS) mensurado por 65 dias e foram pesados a cada 13 dias para obtenção do ganho médio diário (GMD). Foram considerados o peso vivo inicial (PVI), o peso vivo final (PVF), o peso metabólico (PM), o GMD, a taxa de crescimento relativo (TCR), a taxa de Kleiber (TK), a CA, o CMS e o CMS em percentual do PV (CMSPV). As avaliações de carcaça foram realizadas por ultrassom. O CAR se mostrou correlacionado com o CMS (+0,81), o CMSPV (+0,90) e a CA (+0,63). Correlações significativas foram encontradas entre CA e GMD; CA e TCR; CA e TK; e CA e PVI (-0,63, -0,74, -0,75 e +0,51, respectivamente). O CAR e a CA não se mostraram correlacionados com características de carcaça, e, da mesma forma, não houve diferença entre as classes de CAR para essas variáveis. Confirmou-se o potencial do CAR como medida de eficiência alimentar para cordeiros em confinamento, sem existência de relações com o ganho de peso e o tamanho corporal e sem alterações na composição da carcaça.

The residual feed intake (RFI) and the feed conversion ratio (FCR) of 20 lambs was evaluated in order to estimate the correlations between these traits and performance measures and with in vivo carcass characteristics. The animals had their dry matter intake (DMI) measured over 65 days and they were weighed every 13 days to determine the average daily weight gain (ADG). Initial body weight (IBW), final body weight (FBW), metabolic weight (MW), ADG, relative growth rate (RGR), Kleiber ratio (KR), FCR, DMI and DMI in BW percentual (BWDMI) were considered. The carcass evaluation was performed by ultrasound. The RFI was correlated with the DMI (+0.81), BWDMI (+0.90) and with FCR (+0.63). Significant correlations were found between FCR and ADG; FCR and RGR; and FCR and KR; and FCR and IBW (-0.63, -0.74, -0.75 and +0.51 respectively). The RFI and the FCR were not correlated with carcass traits and similarly there was no difference between the RFI-classes for these variables. It was proved the RFI has potential as a measure of feed efficiency for housed lambs, without the existence of relations with weight gain and body size of animals and without changes in carcass composition.

Cyclosporin A and trifluoperazine, two resistance-modulating agents, increase ivermectin neurotoxicity in mice.

The P-glycoprotein expressed in the blood-brain barrier has been associated with the restricted access of many compounds to the central nervous system. Mice lacking the mdr1a P-glycoprotein gene show an accumulation of various drugs in brain tissues. P-glycoprotein is also correlated with the phenomenon of multidrug resistance in tumour cells. To investigate the effects of drugs that modulate multidrug resistance in the selective permeability of the blood-brain barrier, mice were treated with cyclosporin A or trifluoperazine plus ivermectin, a P-glycoprotein substrate, that has a limited access to the central nervous system. When mice received an injection of cyclosporin A (50 mg/kg, intraperitoneally) or trifluoperazine (750 microg/kg, intraperitoneally) one hour prior to the administration of ivermectin (10-15 mg/kg, intraperitoneally) there was an increase in the acute toxicity of ivermectin. HPLC analysis of brain tissues indicated that the ivermectin brain concentration was 2.5 times higher when mice were previously treated with cyclosporin A (50 mg/kg). These results suggest that attention should be given to the side effects of drugs that interact with P-glycoprotein and are commonly used clinically and also to the possibility of creating a pharmacological gap in the blood-brain barrier that allows the access of chemotherapeutic drugs to brain tumours.

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.

In vitro radioautographic studies of the biodistribution of radiopharmaceuticals on blood elements

In the present study evaluated the binding of the radiopharmaceuticals sodium pertechnetate (Na (99m)TcO4), methylenediphosphonic acid (99m)Tc-MDP)) and glucoheptonate acid (99m)Tc-GHA)) to blood elements using centrifugation and radioautographic techniques. Heparinized blood was incubated with the labelled compounds for 0, 1, 2, 3, 4, 6 and 24 h. Plasma (P) and blood cells (BC) were isolated and precipitated with 5 percent trichloroacetic acid (TCA), and soluble (SF) and isoluble fractions (IF) were separated. Blood samples were prepared (0 and 24 h) and coated with LM-1 radioautographic emulsions and percent radioactivity (percent rad) in P and BC was determined. The binding of Na (99m)TcO4 (percentrad) to P was 61.2 percent (0 h) and 46.0 percent (24 h), and radioautography showed 63.7 percent (0 h) and 43.3 percent (24 h). The binding to BC was 38.8 percent (0 h) and 54.0 percent (24 h), and radioautography showed 36.3 percent (0h) and 56.7 percent (24 h), and radioautography showed 36.3 percent (0 h) and 56.7 percent (24 h). (99m) Tc-MDP study presented 91.1 percent (0 h) to P and 87.2 percent (24 h), and radioautography showed 67.9 percent (0 h) and 67.4 percent (24 h). The binding to BC was 8.9 percent (0 h) and 12.8 percent (24 h), and radioautography showed 32.1 percent (0 h) and 32.6 percent (24 h). (99m)Tc-GHA study was 90.1 percent (0 h) to P and 79.9 percent (24 h), and radioautography showed 67.2 percent (0 h) and 60.1 percent (24 h). The binding to BC was 9.9 percent (0 h) and 20.1 percent (24 h), and radioautography showed 32.8 percent (0 h) and 39.9 percent (24 h). The comparasion of the obtained results suggests that the binding to plasma and blood cells in the two techniques used (radioautography and centrifugation) qualitatively in accordance.

Effect of cyclophosphamide on the binding of 99mTcO4 and 99mTc-MDP to blood cells and plasma proteins

Since the introduction of technetium-99m (99mTc) and its rapid acceptance as a tool in nuclear medicine, very little information is available about is biological action as 99mTc-radiopharmaceuticals. We have determined if cyclophosphamide, an alkylating agent, used in oncology as a chemotherapeutic drug, modifies the binding of 99mTCO-4 and 99mTc-MDP (99mTc-metylenediphosphonic acid) to blood cells and to plasma proteins. The radiopharmaceuticals were injected intravenously (iv) into SW-55 mice (male and female, weight 25 g) and samples of plasma and blood cells were separated. Cyclophosphamide (50 µg) was injected iv 1 h before the radipharmaceuticals. Samples of plasma and blood cells were also precipitated with 5 per cent trichloroacetic acid and soluble and insoluble fractions were isolated. The following results were obtained: 1) cyclophosphamide did not alter (0.25 to 8h) percent radioactivity of 99m TcO04 in plasma or blood cells but increased the binding of 99m Tc-MDP to blood cells; 2) cyclophosphamide did not alter (o.25 to 8h) 6the binding of 99m TcO-4 in insoluble fraction of plasma and decreasde (1 to 4h) percent radioactivity of 99mTc-MDP in the insoluble fraction of plasma; 3) cyclophosphamide increased (0.25 to 4h) percent radioactivity of 99mTcO-4 in the insoluble fraction of blood cells but did not alter the binding of 99m Tc-MDP. Cyclophosphamide and/ or its methabolities modified the effective half-life of these radiopharmaceuticals (to 99TcO-4 was increased 2.3 to 3.4h and to 99mTc-MDP was decreased 3.3 to 2.1 h) and possibly increased the permeability of blood cells to 99m TcO-4

In vitro effect of cyclophosphamide on the binding of radiopharmaceuticals (99mTcO4 and 99mTc-MDP) to blood elements

Sodium pertechnetate (99mTcO4) and many99m Tc-products are the radiopharmaceuticals most frequently used in nuclear medicine. Using an in vitro model, we evaluated the effect of cyclophosphamide on per cent radioactivity of 99mTcO4 and methylenedi-phosphonic acid (99mTc-MDP) bound toi isolated blood elements. Blood samples were incubated with the two radiopharmaceuticals, plasma and blood cells were separated and precipitated, and soluble and insoluble fractions were separated. To evaluate the effect of cyclophosphamide, blood was incubated with this drug 1h prior to the addition of the radiopharmaceuticals. The fraction of 99mTcO4 radioactivity was slightly higher in plasma (61.2 to 53.8 per cent) than in blood cells (38.8 to 46.2 per cent) up to 6 h and cyclophosphamide did not interfere with this distribution. The amount of 99mTc-mdp radioactivity was higher in plasma (91.1 to 87.2 per cent) than in blood cells 8.9 to 12.9 per cent) up to 24 h and cyclophosphamide did not modify it. The binding of 99mTcO4 to the insoluble fraction of plasma (4.9 to 6.1 per cent) was low and cyclophosphamide did not interfere with it up to 6h, but a small blockade (9.8 to 4.8 per cent) was observed at 24 h. From 3 h on, cyclophosphamide slightly inhibited 99mTcO4 binding to blood cells (23.1 to 16.6 per cent) and increased it at 24h (31.2 to 14.3 per cent). Cyclophosphamide did not alter 99mTc-MDP binding to the insoluble fraction of blood cells and slightly decreased 99mTc-MDP binding to the insoluble fraction of plasma (29.8 to 23.6 per cent) up to 6 h. The effect of cyclophosphamide was strongest at 24 h, with decreased radioactivity binding to the insoluble fraction of plasma (47.6 to 27.0 per cent) and blood cells (51.2 to 23.2 per cent). The fact that cyclophosphamide can bind to plasma proteins and/or cross the cell membrne explains in part the results obtained. Studies using other chemotherapeutic drugs may lead to the development of an in vitro model for the evaluation of drug interaction with radiopharmaceutical substances