Cardiac effects of the extract and active components of radix stephaniae tetrandrae I. Electrically-induced intracellular calcium transient and protein release during the calcium paradox

The present study was designed to compare the cardiac actions of the extrac t and individual components, tetrandrine (Tet) and fangchinoline (Fan), of Radix stephaniae tetrandrae (RST). We measured the electrically induced [Ca 2+](i) transient in single rat ventricular myocytes and protein release fol lowing perfusion with a Ca2+ free solution (the Ca2+ paradox) from the isol ated perfused rat heart, both of which are known to relate to Ca2+ influx. We found that Tet inhibited both electrically induced [Ca2+](i) transient a nd protein release during the Ca2+ paradox, while Fan had no significant ef fects. The RST extract containing 9% Tet and 6% Fan by weight also affected the [Ca2+](i) transient, and was only slightly, though significantly, less effective/potent than Tet alone. On the other hand, RST extract had a sign ificantly greater inhibitory effect on protein release during the Ca2+ para dox than Tet alone. The observations suggest that the RST extract, which co ntains a mixture of components, may have more potent effects in the heart t han its main active component. (C) 2001 Elsevier Science Inc. All rights re served.