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Characterization of rat heart alkaline phosphatase isoenzymes and modulation of activity

2008; Associação Brasileira de Divulgação Científica; Volume: 41; Issue: 7 Linguagem: Inglês

10.1590/s0100-879x2008000700009

1414-431X

Ana Mota, Patrı́cia Silva, Delminda Neves, Clara Lemos, Conceição Calhau, Duarte Torres, Fátima Martel, Hugo Fraga, Laura Ribeiro, Manuel N.M.P. Alçada, Maria João Pinho, Rita Negrão, Rui Pedrosa, Susana G. Guerreiro, João Tiago Guimarães, Isabel Azevedo, Maria João Martins,

Folate and B Vitamins Research

Alkaline phosphatase (ALP) is important in calcification and its expression seems to be associated with the inflammatory process. We investigated the in vitro acute effects of compounds used for the prevention or treatment of cardiovascular diseases on total ALP activity from male Wistar rat heart homogenate. ALP activity was determined by quantifying, at 410 nm, the p-nitrophenol released from p-nitrophenylphosphate (substrate in Tris buffer, pH 10.4). Using specific inhibitors of ALP activity and the reverse transcription-polymerase chain reaction, we showed that the rat heart had high ALP activity (31.73 ± 3.43 nmol p-nitrophenol·mg protein-1·min-1): mainly tissue-nonspecific ALP but also tissue-specific intestinal ALP type II. Both ALP isoenzymes presented myocardial localization (striated pattern) by immunofluorescence. ALP was inhibited a) strongly by 0.5 mM levamisole, 2 mM theophylline and 2 mM aspirin (91, 77 and 84%, respectively) and b) less strongly by 2 mM L-phenylalanine, 100 mL polyphenol-rich beverages and 0.5 mM progesterone (24, 21 to 29 and 11%, respectively). β-estradiol and caffeine (0.5 and 2 mM) had no effect; 0.5 mM simvastatin and 2 mM atenolol activated ALP (32 and 36%, respectively). Propranolol (2 mM) tended to activate ALP activity and corticosterone activated (18%) and inhibited (13%) (0.5 and 2 mM, respectively). We report, for the first time, that the rat heart expresses intestinal ALP type II and has high total ALP activity. ALP activity was inhibited by compounds used in the prevention of cardiovascular pathology. ALP manipulation in vivo may constitute an additional target for intervention in cardiovascular diseases.