_Article_  
Forced Swim Alters the Radiolabeling of Blood Constituents from Wistar Rats  
**[PERSON] 1,2, [PERSON] 3, [PERSON] 2,3,**  
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**[PERSON] 4, [PERSON] 4,5,**  
**[PERSON] 4, [PERSON] 4,6, [PERSON] 4,**  
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1 Departamento de Ciencias Fisisologicas, Instituto Biomedico, Universidade Federal do Estado do Rio de Janeiro, [PERSON], 94, Rio de Janeiro 20211-040, Brazil; [EMAIL_ADDRESS]  
2 Departamento de Biofisica e Biometria, Universidade do Estado do Rio de Janeiro, Instituto de Biologia [PERSON], Avenida 28 de Setembro, 87, 4\({}^{\circ}\) Andar, Vila Isabel, Rio de Janeiro 20551-030, Brazil; [EMAIL_ADDRESS] (M.O.P.); [EMAIL_ADDRESS] (N.R.A.)  
3 Faculdade de Nutricao, Universidade Federal Fluminense, Rua [PERSON], 30, Centro, Niteroi, Rio de Janeiro 24020-140, Brazil; [EMAIL_ADDRESS]  
4 Laboratorio de Vivacgies Meccanica e Praticas Interastivas, Departamento de Biofisica e Biometria, Instituto de Biologia [PERSON] e [PERSON], Universidade do Estado do Rio de Janeiro, Rio de Janeiro 20950-003, Brazil; [PERSON](A.L.B.D.C.); [EMAIL_ADDRESS] (E.H.F.F.F.); [PERSON].M.-F.); [EMAIL_ADDRESS] (D.B.-S.); [EMAIL_ADDRESS] (A.G.M.); [EMAIL_ADDRESS] (C.S.-F.); [EMAIL_ADDRESS] (T.E.-S.); [PERSON].S.G.); [EMAIL_ADDRESS] (L.L.P.-D.); [EMAIL_ADDRESS] (D.C.S.-C.); [EMAIL_ADDRESS] (M.B.-F.)  
5 Programa de Pos-Graduacao em Fisiopatologia Clinica e Experimental, Instituto de Biologia Roberto Alcantara Gomes, Universidade do Estado do Rio de Janeiro, Rio de Janeiro 20551-030, Brazil  
6 Mestrado Profissional em Saude, Medicina Laboratori e Tecnologia Forense, Universidade do Estado do Rio de Janeiro 20950-003, Brazil  
7 Programa de Pos-Graduacao em Ciencias Medicas, Faculdade de Ciencias Medicas, Universidade do Estado do Rio de Janeiro, Rio de Janeiro 20551-030, Brazil  
8 Faculdade Bezerra de Araujo, R. Carius, 179--Campo Grande, Rio de Janeiro 23052-180, Brazil  
9 Groupe de Recherche en Sciences Pour l'Ingenieur (GRESPI), Universite de Reims, 51100 Reims, France  
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Received: 27 December 2019; Accepted: 2 February 2020; Published: 7 February 2020  
**Abstract:** The present study investigated the effects of forced swimming on the technetium-99m (\({}^{99\text{m}}\)Tc) labeling of blood constituents (BloCs). Rats (_Wistar_) were submitted to forced swim. In previous experiments, swimming animals would recover for different periods of time. Animals not submitted to swimming were used as control. Blood samples were obtained and the \({}^{99\text{m}}\)Tc labeling of BloCs was carried out. Blood cells (BCs), plasma (P), insoluble fractions (IF-P and IF-BCs), and soluble fractions (SF-P and SF-BC) were isolated. Radioactivity was determined, and the percentage of \({}^{99\text{m}}\)Tc incorporated (%ATI) was calculated in each fraction. Results showed that forced swimming decreased the percentage of \({}^{99\text{m}}\)Tc incorporated (%ATI) in IF-P (\(p<0.05\)). It is suggested that the \({}^{99\text{m}}\)Tc labeling of BloCs could be used to verify the effects of the stress conditions on BloCs and that the radionuclide fixation on plasma proteins might be altered in rats submitted to acute stress induced by forced swimming, returning to control levels after recovery.  
**Keywords:** blood constituents; forced swimming; stress; technetium-99m