Abstract
Effects of exogenous adenosine 5′-triphosphate (ATP) were studied by measurements of intracellular Ca2+ concentration ([Ca2+]i) and membrane currents in myocytes freshly isolated from the human saphenous vein. At a holding potential of −60 mV, ATP (10 μM) elicited a transient inward current and increased [Ca2+]i. These effects of ATP were inhibited by α,β-methylene adenosine 5′-triphosphate (AMPCPP, 10 μM). The ATP-gated current corresponded to a non-selective cation conductance allowing Ca2+ entry. The ATP-induced [Ca2+]i rise was abolished in Ca2+-free solution and was reduced to 30.1±5.5% (n=14) of the control response when ATP was applied immediately after caffeine, and to 23.7±3.8% (n=11) in the presence of thapsigargin. The Ca2+-induced Ca2+ release blocker tetracaine inhibited the rise in [Ca2+]i induced by both caffeine and ATP, with apparent inhibitory constants of 70 μM and 100 μM, respectively. Of the ATP-induced increase in [Ca2+]i 29.3±3.9% (n=8) was tetracaine resistant. It is concluded that the effects of ATP in human saphenous vein myocytes are only mediated by activation of P2x receptor channels. The ATP-induced [Ca2+]i rise is due to both Ca2+ entry and Ca2+ release activated by Ca2+ ions that enter the cell through P2x receptor channels.
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Loirand, G., Pacaud, P. Mechanism of the ATP-induced rise in cytosolic Ca2+ in freshly isolated smooth muscle cells from human saphenous vein. Pflügers Arch 430, 429–436 (1995). https://doi.org/10.1007/BF00373919
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DOI: https://doi.org/10.1007/BF00373919