Effects of tetrandrine on cytosolic free calcium in cultured rat myocardial cells.
OBJECTIVE
To study the effects of tetrandrine (Tet) on myocardium.


METHODS
Using Fura 2-AM and AR-CM-MIC cation measurement system, cytosolic free calcium ([Ca2+]i) was examined in cultured rat single myocardial cells.


RESULTS
The resting [Ca2+]i was 90 +/- 12 nmol.L-1 in the presence of Ca2+ 1.3 mmol.L-1 in Hanks' solution. Tet 1-100 mumol.L-1 had no effect on the resting [Ca2+]i, but 10-100 mumol.L-1 depressed the [Ca2+]i elevation when extracellular Ca2+ was 5 mmol.L-1. Tet 1-100 mumol.L-1 inhibited KC1 (30 and 60 mmol.L-1) induced [Ca2+]i elevation in a concentration-dependent manner, the IC50 value was 8.8 mumol.L-1 (95% confidence limits: 3.3-23.7 mumol.L-1) and 6.9 mumol.L-1 (95% confidence limits: 2.8-17.4 mumol.L-1), respectively. Norepinephrine (NE) 10 mumol.L-1 caused a rapid increase in [Ca2+]i in the presence or absence of extracellular Ca2+, Tet 30-100 mumol.L-1 only decreased the former. Tet 10-100 mumol.L-1 also decreased ouabain (Oua)-induced elevation in [Ca2+]i.


CONCLUSIONS
Tet had inhibitory effects on Ca2+ transmembrane movement, but it is not a selective calcium channel blocker in rat myocardial cells.
Li
X T
XT
Department of Pharmacology, Nanjing Medical University, China.
Wang
Y L
YL
Wang
J X
JX
Yang
S J
SJ
D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D044182:Benzylisoquinolines; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002478:Cells, Cultured; D009206:Myocardium / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000470:Alkaloids; D044182:Benzylisoquinolines; D002121:Calcium Channel Blockers; C009438:tetrandrine; D002118:Calcium