Extracellular ATP induces Ca2+ transients in cardiac myocytes which are potentiated by norepinephrine

[摘要]

Isolated rat ventricular cardiac myocytes loaded with the fluorescent calcium indicator fura2 showed significant changes in intracellular calcium concentrations upon exposure to > 1 μM ATP (EC₅₀ = 7.4 ± 1.3 μM, n = 4, SE), suggesting that extracellular ATP may have an important influence on myocardial contractility. The response was found to be highly ATP specific and required extracellular calcium. Furthermore, 30 s pretreatment of the cells with 0.2–1 μM norepinephrine decreased the concentration of ATP required for the Ca²⁺ transient, shifting the EC₅₀ for ATP to 1.7 ± 0.1 μM (n = 3, SE). β-Propranolol (a β₁-receptor antagonist) prevented potentiation, whereas phentolamine (an α₁-receptor antagonist) did not, indicating that regulation is through the β₁-adrenergic receptor. ATP and norepinephrine released locally from sympathetic neurons may act in concert through the ATP and β₁-adrenergic receptors to regulate myocardial calcium homeostasis.

[学科分类] 生物化学/生物物理

[关键词] Myocyte;ATP;Norepinephrine;Ca2+ transient;Fura2;BSA;bovine serum albumin;ITP;inosine 5′-triphosphate;UTP;uridine 5′-triphosphate;AMP-PNP;5′-adenylyl imidophosphate;ATPγS;adenosine 5′-O-(3-thiotriphosphate)