Data/hora: 10/06/2024 14:56:02

Provedor de dados: | Brazilian Journal of Medical and Biological Research
País: | Brazil
Título: | Inhibition of the sarcoplasmic reticulum Ca2+ pump with thapsigargin to estimate the contribution of Na+-Ca2+ exchange to ventricular myocyte relaxation
Autores: | Bassani,R.A.; Bassani,J.W.M.
Data: | 2003-12-01
Ano: | 2003
Palavras-chave: | Myocardium; Relaxation; Calcium fluxes; Sodium-calcium exchanger; Sarcoplasmic reticulum calcium ATPase; Caffeine.
Resumo: | Relaxation in the mammalian ventricle is initiated by Ca2+ removal from the cytosol, which is performed by three main transport systems: sarcoplasmic reticulum Ca2+-ATPase (SR-A), Na+-Ca2+ exchanger (NCX) and the so-called slow mechanisms (sarcolemmal Ca2+-ATPase and mitochondrial Ca2+ uptake). To estimate the relative contribution of each system to twitch relaxation, SR Ca2+ accumulation must be selectively inhibited, usually by the application of high caffeine concentrations. However, caffeine has been reported to often cause changes in membrane potential due to NCX-generated inward current, which compromises the reliability of its use. In the present study, we estimated integrated Ca2+ fluxes carried by SR-A, NCX and slow mechanisms during twitch relaxation, and compared the results when using caffeine application (Cf-NT) and an electrically evoked twitch after inhibition of SR-A with thapsigargin (TG-TW). Ca2+ transients were measured in 20 isolated adult rat ventricular myocytes with indo-1. For transients in which one or more transporters were inhibited, Ca2+ fluxes were estimated from the measured free Ca2+ concentration and myocardial Ca2+ buffering characteristics. NCX-mediated integrated Ca2+ flux was significantly higher with TG-TW than with Cf-NT (12 vs 7 µM), whereas SR-dependent flux was lower with TG-TW (77 vs 81 µM). The relative participations of NCX (12.5 vs 8% with TG-TW and Cf-NT, respectively) and SR-A (85 vs 89.5% with TG-TW and Cf-NT, respectively) in total relaxation-associated Ca2+ flux were also significantly different. We thus propose TG-TW as a reliable alternative to estimate NCX contribution to twitch relaxation in this kind of analysis.
Tipo: | Info:eu-repo/semantics/other
Idioma: | Inglês
Identificador: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2003001200014
Editor: | Associação Brasileira de Divulgação Científica
Relação: | 10.1590/S0100-879X2003001200014
Formato: | text/html
Fonte: | Brazilian Journal of Medical and Biological Research  v.36 n.12 2003
Fonte: | info:eu-repo/semantics/openAccess