Cardiac contractility of the African sharptooth catfish, Clarias gariepinus: role of extracellular Ca2+, sarcoplasmic reticulum, and β-adrenergic stimulation

• Autor(a) principal: Monteiro, Diana Amaral
• Data de Publicação: 2021
• Outros Autores: Lopes, André Guelli [UNESP], Jejcic, Nathalia Usun, da Silva Vasconcelos, Eliton [UNESP], Kalinin, Ana Lúcia, Rantin, Francisco Tadeu
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://dx.doi.org/10.1007/s10695-021-01023-7; http://hdl.handle.net/11449/229716
• topic: Cardiac function; Facultative air-breathing fish; Force-frequency relationship; NCX; PLN; SERCA

This study investigated the dependence of contraction from extracellular Ca2+, the presence of a functional sarcoplasmic reticulum (SR), and the effects of β-adrenergic stimulation using isometric cardiac muscle preparations. Moreover, the expression of Ca2+-handling proteins such as SR-Ca2+-ATPase (SERCA), phospholamban (PLN), and Na+/Ca2+ exchanger (NCX) were also evaluated in the ventricular tissue of adult African sharptooth catfish, Clarias gariepinus, a facultative air-breathing fish. In summary, we observed that (1) contractility was strongly regulated by extracellular Ca2+; (2) inhibition of SR Ca2+-release by application of ryanodine reduced steady-state force production; (3) ventricular myocardium exhibited clear post-rest decay, even in the presence of ryanodine, indicating a decrease in SR Ca2+ content and NCX as the main pathway for Ca2+ extrusion; (4) a positive force-frequency relationship was observed above 60 bpm (1.0 Hz); (5) ventricular tissue was responsive to β-adrenergic stimulation, which caused significant increases in twitch force, kept a linear force-frequency relationship from 12 to 96 bpm (0.2 to Hz), and improved the cardiac pumping capacity (CPC); and (6) African catfish myocardium exhibited similar expression patterns of NCX, SERCA, and PLN, corroborating our findings that both mechanisms for Ca2+ transport across the SR and sarcolemma contribute to Ca2+ activator. In conclusion, this fish species displays great physiological plasticity of E-C coupling, able to improve the ability to maintain cardiac performance under physiological conditions to ecological and/or adverse environmental conditions, such as hypoxic air-breathing activity.