The reduced myofilament responsiveness to calcium contributes to the negative force-frequency relationship in rat cardiomyocytes: role of reactive oxygen species and p-38 map kinase.
Pflugers Arch
; 469(12): 1663-1673, 2017 Dec.
Article
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| MEDLINE
| ID: mdl-28836001
The force-frequency relationship (FFR) is an important intrinsic regulatory mechanism of cardiac contractility. However, a decrease (negative FFR) or no effect (flat FFR) on contractile force in response to an elevation of heart rate is present in the normal rat or in human heart failure. Reactive oxygen species (ROS) can act as intracellular signaling molecules activating diverse kinases as calcium-calmodulin-dependent protein kinase II (CaMKII) and p-38 MAP kinase (p-38K). Our aim was to elucidate the intracellular molecules implicated in the FFR of isolated rat ventricular myocytes. The myocytes were field-stimulated via two-platinum electrodes. Sarcomere length was recorded with a video camera. Ca2+ transients and intracellular pHi were recorded by epifluorescence. Increasing frequency from 0.5 to 3 Hz decreased cell shortening without changes in pHi. This negative FFR was changed to positive FFR when the myocytes were pre-incubated with the ROS scavenger MPG, the NADPH oxidase blocker apocynin, or by inhibiting mitochondrial ROS production with 5-HD. Similar results were obtained when the cells were pre-incubated with the CaMKII blocker, KN-93, or the p-38K inhibitor, SB-202190. Consistently, the levels of phosphorylation of p-38K and the oxidation of CaMKII were significantly higher at 2 Hz than at 0.5 Hz. Despite the presence of positive inotropic effect during stimulation frequency enhancement, Ca2+ transient amplitudes were reduced in MPG- and SB-202190-treated myocytes. In conclusion, our results indicate that the activation of the intracellular pathway involving ROS-CaMKII-p-38K contributes to the negative FFR of rat cardiomyocytes, likely by desensitizing the response of contractile myofilaments to Ca2+.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Especies Reactivas de Oxígeno
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Miocitos Cardíacos
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Proteínas Quinasas p38 Activadas por Mitógenos
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Contracción Miocárdica
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Miofibrillas
Límite:
Animals
Idioma:
En
Revista:
Pflugers Arch
Año:
2017
Tipo del documento:
Article
País de afiliación:
Argentina
Pais de publicación:
Alemania