Effect of a peel passion fruit flour (Passiflora edulis f. flavicarpa) extract on the labeling of blood constituents with technetium-99m and on the morphology of red blood cells

RADIOPHARMACEUTICAL RESEARCH AND DRUG INTERACTION

Effect of a peel passion fruit flour (Passiflora edulis f. flavicarpa) extract on the labeling of blood constituents with technetium-99m and on the morphology of red blood cells

Bernardo Machado Rebello^I,II,*; Silvana Ramos Farias Moreno^II,III; Camila Godinho Ribeiro^I,II; Rosane de Figueiredo Neves^I,II; Adenilson de Souza da Fonseca^I; Luis Querino de Araújo Caldas^III; Mario Bernardo-Filho^I,II; Aldo da Cunha Medeiros^I

^IPrograma de Pós-Graduação em Ciências da Saúde; Universidade Federal do Rio Grande do Norte; Av. Gal. Gustavo Cordeiro de farias, s/n; 59010-180; [e-mail]; Natal - RN - Brasil

^IIDepartamento de Biofísica e Biometria; Instituto de Biologia Roberto Alcântara Gomes; Universidade do Estado do Rio de Janeiro; Av. 28 de Setembro, 87; 20551-030; Rio de Janeiro - RJ - Brasil

^IIIPrograma de Pós-Graduação em Ciências Médicas; Universidade Federal Fluminense; Niterói - RJ - Brasil

ABSTRACT

Passiflora edulis f. flavicarpa (maracuja) is a fruit consumed in Brazil and worldwide. Blood constituents labeled with technetium-99m (99mTc) are used in nuclear medicine. The effect of P. flavicarpa extract on the radiolabeling of blood constituents and on red blood cells morphology was evaluated. Blood samples from Wistar rats was incubated with P. flavicarpa extract. After that, the labeling of blood constituents with 99mTc was carried out. Samples of plasma and blood cells were precipitated with trichloroacetic acid to isolate the soluble and insoluble fractions of plasma and blood cells. The radioactivity in each fractions was counted and the percentage of radioactivity was determined. Blood smears were also prepared to morphological evaluation and perimeter/area ratio determination. P. flavicarpa extract altered (p<0.05) the fixation of ^99mTc on plasma proteins and the perimeter/area ratio of red blood cells. Substances present in P. flavicarpa extract could affect the labeling of blood constituents with ^99mTc acting in specific targets as membrane of red blood cells.

Key words: Labeling, Blood, Passiflora edulis f. flavicarpa, Radiobiocomplexes, technetium-99m

RESUMO

Passiflora edulis f. flavicarpa (maracujá) é um fruto consumido no Brasil e no mundo. O efeito de um extrato de farinha da casca de maracujá na marcação dos constituintes sangüíneos com tecnécio-99m e na morfologia de hemácias foi avaliado. Amostras de sangue de ratos Wistar, foram incubadas com extrato de P. flavicarpa. Em seguida, o procedimento de marcação de constituintes sangüíneos com Tc-99m foi realizado. Amostras de plasma e células sangüíneas foram separadas e alíquotas destas frações foram precipitadas com ácido tricloroacético para isolamento das frações solúvel e insolúvel do plasma e das células sangüíneas. A radiatividade em cada fração foi contada a porcentagem de radioatividade (%ATI) foi calculada. Distensões sangüíneas foram também preparadas para avaliação morfológica e da relação perímetro/área de hemácias. O extrato de P. flavicarpa alterou a fixação do ^99mTc nas proteínas plasmáticas e a relação perímetro/área das hemácias. Substâncias presentes no extrato de P. flavicarpa poderiam afetar a marcação de constituintes sangüíneos com ^99mTc atuando em alvos específicos, como a membrana das hemácias.

INTRODUCTION

Passion fruit, Passiflora edulis f. flavicarpa (P. flavicarpa) is a fruit widely consumed worldwide and in Brazil is commonly known as "maracujá". The pulp of this fruit contains ascorbic acid and carotenoids (Talcoot et al., 2003). The passion fruit peel corresponds to 60% of the fruit and it contains pectin (21.5%), tryptophan, grax acid and sulphured aminoacids (Guertzenstein, 1998). It has been reported some benefic effects of the P. flavicarpa flour in Wistar diabetic rats, such as cholesterol level reduction, increased glucose tolerance, prolonging gastric-emptying half-time, (Guertzenstein, 1998) increased protein metabolism (Pirman et al., 2007).

There are also studies in human suggesting an effect of pectin in reduction of cholesterol (Guertzenstein, 1998; Schwiezer et al., 1991), glucose blood levels (Schwartz et al., 1988) and glucose absorption in human intestine (Fuse et al., 1989).

Technetium-99m (^99mTc) is the most utilized radionuclide in nuclear medicine to obtain single photon emission computed tomography (SPECT). Its wide use in nuclear medicine is due to its optimal characteristics (half-life of 6h, gamma ray energy of 140 keV, easily obtained from a 99Mo/99mTc generator, minimal dose to the patient and negligible environmental impact) (Hladik III et al,. 1987). The chemical form of the ^99mTc obtained from the generator is sodium pertechnetate (Na^99mTcO₄). This ion has an oxidation number +7, which is practilly nonreactive and can not label any compound (Saha, 2004). The labeling of some biocomplexes (Moreno et al., 2004; Bernardo-Filho et al., 2005) needs a reducing agent and stannous chloride (SnCl₂) is the most utilized with this purpose (Saha, 2004).

Red blood cells (RBC) labeled with ^99mTc are used in research (Moreno et al., 2004; Bernardo-Filho et al., 2005; Santos-Filho et al., 2005, Freitas et al., 2007) and in many procedures of nuclear medicine, including studies for spleen localization, gastrointestinal bleeding sites, blood cells mass localization, cardiovascular system studies, placental studies (Saha, 2004).

Plasma proteins (macroaggregated albumin) can be labeled with 99mTc and it can be used for lung perfusion imaging (Saha, 2004).

Sequential steps of the intracellular labeling process of the RBC include: (i) transmembrane transport of stannous and pertechnetate ionsinto internal compartment of RBC; (ii) reduction of ^99mTc (^99mTcO₄)by the SnCl₂ and (iv) binding of the reduced ^99mTc to hemoglobin (Callahan and Rabito, 1990).

Due the importance of the labeled blood constituents in nuclear medicine, the aim of this study was to evaluate the effect of a P. flavicarpa extract on the labeling of blood constituents with 99mTc and on the morphology of red blood cells using an in vitro experimental model.

MATERIALS AND METHODS

Wistar male rats (250-300g, 3-4 months) were obtained from the Laboratório de Radiofarmácia Experimental (Departamento de Biofísica e Biometria, Universidade do Estado do Rio de Janeiro, RJ, Brazil). They were maintained under controlled room conditions (22± 5º C, 12 h of light/dark cycle), water and normal diet (ad libitum). Experiments were conducted in accordance with the Department Committee of Animal Care of this University (Protocol number CEA/133/2006).

A commercial of Peel Passion Fruit Flour was obtained from A.S.S. Neto´s Alimentos LTDA., Rio de Janeiro, Brazil, (Lot 0001415).

In the preparation of the extract, 0.5g of the flour was diluted to 10mL in saline solution (0.9% NaCl) and shacked (2 minutes). The preparation was centrifuged (clinical centrifuge, 5 minutes, 1500 rpm). The supernatant solution was retired and considered 100% (50mg/mL) solution. The concentrations 25mg/mL, 12.5mg/mL, 6.25mg/mL and 3.12mg/mL were also obtained with successive dilutions in saline solution.

A spectrophotometric analysis (Analyser, 800M, São Paulo, Brazil) of P. flavicarpa extract was carried out. The absorbance at 480 nm was considered the marker of the quality control of this extract. All the prepared extracts to be used in the experiments must have the optical density close to 0.18 (Fig. 1) to be used in the experiments.

Blood samples (0.5mL) were incubated with 100µL of different concentrations of P. flavicarpa extract for 60 minutes at room temperature. As control, samples of heparinized whole blood were incubated with 0.9% NaCl solution. After this period of time, 0.5mL of stannous chloride (Sigma Chemical Co., USA) (1.2µg/mL) solution (freshly prepared) were added and incubated for more 60 minutes. Then, 0.1mL (3.7MBq) of 99mTc, as sodium pertechnetate, (Instituto de Pesquisas Energéticas e Nucleares, Comissão Nacional de Energia Nuclear, São Paulo, Brazil) was added and the incubation continued for more 10 minutes. These samples were centrifuged and plasma (P) and cells (BC) were separated. Samples (20µL) of P and BC were also precipitated with 1ml of 5% trichloracetic acid (TCA) and insoluble (IF) and soluble fractions (SF) isolated. The radioactivity of the samples was determined in a well counter (Automatic Gamma Counter, C5002, Packard, USA). After that, the percentage of radioactivity (%ATI) was calculated as described elsewhere (Bernardo-Filho et al. 1983).

The morphometry study of the red blood cells was also performed with the samples of blood incubated with P. flavicarpa extract (all concentrations). One drop of each sample was smeared in glass slides (5 slides for each sample) and the May-Grünwald-Giemsa method was performed (Junqueira and Carneiro, 2004). The smears were evaluated under a light microscope of clear field (Eclipse E 400^TM), in the immersion objective (100x), with photographer ocular. Quantification of the data was realized by Software image pro plus (media Cyberbetics)

Statistical analysis (Kruskal-Wallis with post-test Dunns, p<0.05) was used to compare the experimental data with the controls.

RESULTS

The Fig. 1 shows the absorbance spectrum of a Passiflora edulis f. flavicarpa extract. The data in this figure indicate that the main absorbance peak (0.18) of this P. flavicarpa extract occurs at 480 nm.

Table 1 shows the effect of the P. flavicarpa extract on the distribution of the radioactivity in plasma and cellular compartments. The results indicate no significant (p>0.05) alteration of the distribution of ^99mTc between plasma and cellular compartments.

Table 2 shows the fixation of the radioactivity on the plasma proteins. The results indicate that there is a significant decrease (p<0.05) of the fixation of ^99mTc on the insoluble fraction of plasma at the highest concentrations.

Table 3 shows the fixation of the radioactivity on blood cell proteins. The results indicates no significant (p>0.05) alteration on the fixation of ^99mTc on soluble and insoluble fractions of the blood cells.

The qualitative analysis of the shape of red blood cells from blood samples treated with P. flavicarpa extract has shown important morphological alterations in the red blood cells. Some blood cells have presented spikes on the membrane (Fig. 3).These alterations were not found when blood samples were incubated with 0.9% NaCl solution, which presented cells with a normal and characteristic shape (Fig. 2).

A morphometric parameter (perimeter/area ratio) of the red blood cells was also significantly altered (p<0.05) when blood samples were treated with P. flavicarpa extract (Table 4).

DISCUSSION

Although there is great variety of medicinal plants, there is not so much data relating natural products correct identification of their chemical composition, collateral effects, therapeutic properties and some biological properties (Messina, 2006). The radiolabeling of blood constituents has a great importance in nuclear medicine (Saha, 2004). Some authors have suggested that drugs could alter the radiolabeling of blood constituents (Moreno et al., 2002; Abreu et al., 2006; Silva et al., 2006), as well as, promote morphological alterations on the erythrocyte membrane (Braga et al., 2000; Oliveira et al., 2002; Oliveira et al., 2003; Santos-Filho et al., 2004; Moreno et al., 2004). Other studies report that some natural products could not interfere on the radiolabeling of blood constituents (Diré et al., 2004; Fernandez et al., 2005) and could not modify the morphology of the red blood cells (Fernandez et al., 2005).

The analysis of the our results indicates that P. flavicarpa extract decreased the fixation of ^99mTc on plasma proteins and did not alter the labeling of blood cells with ^99mTc. It should be possible that the chemical compounds in P. flavicarpa extract could compete with the ^99mTc (pertechnetate) and/or stannous ions for the binding sites of the plasma proteins decreasing the fixation of ^99mTc on plasma proteins.

The morphological analysis showed an increase of the perimeter/area ratio of red blood cells from blood samples treated with P. flavicarpa extract (50mg/ml). Similar alterations were obtained when blood samples were treated with 25 mg/ml (data not shown). It could be suggested that some substances present in the P. flavicarpa extract could promote morphological alterations on the membrane of red blood cells as shown in the Fig. 3. Alterations on the erythrocyte membrane have also been reported to other extracts as Tobacco (Braga et al., 2000), Maytenus ilicifolia (Oliveira et al., 2000), Paulinia cupana (Oliveira et al., 2002), Coffea Arabica (Oliveira et al., 2003), Fucus vesiculosus (Oliveira et al., 2003) and Ginkgo biloba (Moreno et al., 2004). In these studies when the morphological alterations occurred, the red blood cells labeling with ^99mTc was also altered by the extracts. P. flavicarpa extract is capable to modify the erythrocyte membrane morphology, but is not capable to modify the labeling of blood cells. It may possible that the morphological alterations produced by chemical compounds in P. flavicarpa extract on the membrane red blood cells could not interfere on the ions transport mechanism into the cell. In consequence the labeling of the blood cells would be not altered.

ACKNOWLEDGEMENTS

We are grateful for the biologist Mario Pereira (UERJ) for his technical support and to Mr. Carlos Brown Scavarda (B. A., University of Michigan) for the English language revision. Financial support: CNPq, CAPES and UERJ.

Received: July 22, 2007;

Revised: August 08, 2007;

Accepted: September 11, 2007.

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Author for correspondence

Publication Dates

• Publication in this collection
  12 Mar 2008
• Date of issue
  Sept 2007

History

• Received
  22 July 2007
• Reviewed
  08 Aug 2007
• Accepted
  11 Sept 2007