Effect of various agents on the cytoplasmic calcium concentration in cultured human muscle cells |
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Authors: | A E Jacobs A A Benders A Oosterhof J H Veerkamp R A Wevers E G Joosten |
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Affiliation: | Department of Biochemistry, University of Nijmegen, The Netherlands. |
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Abstract: | 1. We determined the cytoplasmic Ca2+ concentration ([Ca2+]i) in cultured human muscle cells using the fluorescent indicator Quin-2. 2. The [Ca2+]i was dependent on the external Ca2+ concentration. Acetylcholine in the presence of external Ca2+ caused a transient increase in [Ca2+]i. Inhibition by nifedipine indicated that this response was mediated through activated voltage-operated channels. In nominally Ca2(+)-free buffer acetylcholine did not markedly increase [Ca2+]i. Therefore, the increase in [Ca2+]i as a response to depolarization is mainly due to influx of external Ca2+. 3. Various concentrations of caffeine did not influence the [Ca2+]i. Dantrolene decreased [Ca2+]i, both in the presence and absence of external Ca2+. The reduction probably resulted from an action of dantrolene on the intracellular Ca2+ stores, since dantrolene did not influence 45Ca2+ influx or efflux and caffeine partially counteracted the reduction. |
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