Abstract
Experiments were performed in bovine chromaffin cells in short term primary culture. Tetrandrine is a plant alkaloid from the chinese medical herb Stefania tetrandra. The aim of the present study was to investigate the mechanisms by which tetrandrine interacts with calcium signalling and to provide a quantitative description of effects. Tetrandrine blocked voltage-operated calcium channel currents concentration-dependently as shown in whole cell patch-clamp recordings. The blockade of calcium channels reduced the potassium-stimulated catecholamine release. Besides, the drug increased the spontaneous (not stimulated) release of catecholamines in the presence of extracellular calcium. Measurements of intracellular calcium levels [Ca]i showed a calcium release from intracellular stores by tetrandrine. This tetrandrine-induced [Ca]i elevation was higher in calcium containing as compared to calcium free solution. Tetrandrine effects partially overlap with those of thapsigargin, but tetrandrine has additional targets, since it increased [Ca]i in cells pretreated with thapsigargin. We conclude that tetrandrine blocks voltage-operated calcium channels and increases [Ca]i by blocking endoplasmic and other calcium pumps.
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Received: 13 October 1997 / Accepted: 14 January 1998
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Bickmeyer, U., Weinsberg, F., Müller, E. et al. Blockade of voltage-operated calcium channels, increase in spontaneous catecholamine release and elevation of intracellular calcium levels in bovine chromaffin cells by the plant alkaloid tetrandrine. Naunyn-Schmiedeberg's Arch Pharmacol 357, 441–445 (1998). https://doi.org/10.1007/PL00005191
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DOI: https://doi.org/10.1007/PL00005191