Extracellularly applied ATP alters the calcium flux through dihydropyridine-sensitive channels in cultured chick myotubes |
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Authors: | H Eriksson E Heilbronn |
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Affiliation: | Unit of Neurochemistry and Neurotoxicology, University of Stockholm, Sweden. |
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Abstract: | Extracellularly applied ATP mediates a biphasic calcium signal in cultured chick myotubes. A rapid and transient increase in cytosolic calcium was independent of extracellular calcium while a second signal, slower in onset and decay, was absent without extracellular calcium. In depolarized myotubes, the cytosolic [Ca2+] was increased more than ten times above baseline level. Addition of ATP to the incubation medium immediately increased the rate of return of cytosolic Ca2+ levels to baseline. The ATP effect was half-maximal at about 10 microM ATP and was mimicked by ATP S. This ATP-sensitive calcium influx was also rapidly stopped by addition of dihydropyridines such as PN 200-110, suggesting that it is the voltage operated Ca2+-channel that was inactivated by ATP. |
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