Basic and Applied Pathology 2010; 3: 134–137 doi:10.1111/j.1755-9294.2010.01093.x ORIGINAL ARTICLE Apoptosis status from rat heart submitted to foot shock stress Regina C ´ elia Spadari-Bratfisch, 1 Viviane de Menezes C ´ aceres, 1 Daniela Ortolani, 1 Viviane Carlin 2 and Daniel Araki Ribeiro 1,2 Departments of 1 Biosciences and 2 Pathology, Federal University of Sao Paulo, Sao Paulo, Brazil Key words apoptosis, bax , bcl-2, p53, physiological, rat heart, stress. Received 29 July 2010 Accepted 22 September 2010 Correspondence Daniel Araki Ribeiro, DDS, PhD, Departamento de Bioci ˆ encias, Avenue Ana Costa, 95-Vila Mathias 11060-001, Santos, Sao Paulo, Brazil. Email: daribeiro@unifesp.br, daribeiro@pesquisador.cnpq.br ABSTRACT Background and aim: The goal of this study was to investigate whether physical stress is able to modulate apoptotic response in rat myocardial tissue. The effects of foot shock stress on the histopatological changes and immunohistochemistry for p53, bcl-2 and bax were evaluated. Methods: Male Wistar rats (n = 10) were distributed into two groups: group 1, control and group 2, stress. The stress pro- tocol consisted of one daily foot-shock session applied on three consecutive days. Results: The results pointed out no remarkable changes of myocardial tissue be- tween groups. Also, the foot shock stress was not able to modulate p53, bcl-2 or bax expression, as depicted by no significant statistically differences (P > 0.05) be- tween groups for all immunomarkers evaluated. Conclusions: Taken together, our results suggest that foot shock stress did not induce histopathological changes in rat myocardial tissue. It seems that physical stress is not able to modulate apoptotic response in rats. Certainly, this finding offers new insights into the mechanisms underlying the relation between apoptosis and cardiac injury after stress. INTRODUCTION The cardiovascular diseases are responsible for at least 50% of all deaths in the occidental world, with one-third of the adult popu- lation suffering from some cardiovascular pathology. The action potential velocity of propagation and the velocity of contraction and relaxation and force of contraction in cardiac muscle cells de- termine cardiac output, which is regulated minute-by-minute, to keep blood pressure constant. 1 Apoptosis is a tightly regulated process of genetically pro- grammed cell death by which senescent, damaged, and superfluous cells are eliminated from the body. Apoptosis is involved in the etiology of many chronic, often degenerative processes, includ- ing cardiac remodeling after myocardial stress. 2 Apoptosis can be triggered in a cell through either the extrinsic pathway or the in- trinsic pathway. The Tp 53 gene encodes a nuclear phosphoprotein, so called the p53 protein. 3 This consists of 393 amino acids and comprises four domains amino-terminal transactivation domain, a core DNA-binding domain, carboxy terminal tetramerization and regulatory domains, with different functions. 4 The gene regulated by p53 protein is involved in cell cycle inhibition, and apoptosis by extrinsic pathway. 5 The bcl-2 proto-oncogene was originally dis- covered by analysis of the t(14; 18) chromosomal translocation as- sociated with human follicular B-cell lymphoma. 6 The bcl-2 gene encodes a membrane protein localized to the nuclear membrane, the inner surface of mitochondria, and the endoplasmic reticulum. 7 It is the most important gene of the bcl-2 family and has been shown to be an inhibitor of apoptosis. 8,9 Bax, another member of the bcl- 2 family, is considered to be a major effector of apoptosis. 10 Bax forms heterodimers with bcl-2, in which its distribution is inversely related to that of bcl-2. 11 Despite the rapid growth in the field of re- search on apoptotic myocyte cell death induced by xenobiotics, the role of apoptotic proteins after stress in rat heart cells has not still been elucidated so far. 12,13 As a result of inappropriate in vivo evidence, the aim of this study was to analyze whether rat heart submitted to foot shock stress is able to induce apoptosis. For this purpose, the histopathological analysis of the myocardial tissue as well as immunohistochem- istry for p53, bcl-2 and bax were performed. Certainly such data will contribute to better understanding on myocardial tissue after physical stress upon cellular system. METHODS Animals All animal procedures were conducted according to the ‘Guidelines for Ethical Care and Use of Experimental Animals’ published by the US National Institute of Health and were approved by the Institutional Ethics Committee of the Federal University of S˜ ao Paulo (UNIFESP). The Central Animal House of UNIFESP provided intact male Wistar rats (n = 10), housed in group cages, fed with rat chow and water ad libitum, and maintained with constant temperature (23 ◦ C) on a 12-h light:dark cycle. The animals were randomly assigned to two groups (five in each group): group 1, control and group 2, stress. Control procedure On the first day of the experiment, each rat was placed in the footshock cage where it remained for 30 min before being returned to the animal care facilities. During this period, the power for the footshock cage was turned off (day 0). On the following three 134