Blocking L-calcium current by l-tetrahydropalmatine in single ventricular myocyte of guinea pigs.
OBJECTIVE
To study the effect of l-tetrahydropalmatine (l-THP) on L-type calcium channel.


METHODS
Patch clamp technique (whole cell recording) was used to record L-Ca2+ current in single cardiac myocyte.


RESULTS
1) l-THP 1, 10, and 100 micromol.L-1 reduced ICa-max from (999 +/- 93) pA to (700 +/- 111) pA, (582 +/- 66) pA, and (420 +/- 112) pA (n = 6, P < 0.01), respectively. 2) l-THP reduced the voltage at half-maximal inactivation (V1/2) of L-Ca2+ channel to more negative potentials by 9 mV (n = 5, P < 0.05). 3) l-THP caused both tonic and use-dependent reduction of Ca2+ current. Tonic block of l-THP on Ca2+ current was 46% +/- 8% (n = 6, P < 0.01). The degree of use dependent blocking was 13.5% +/- 2.4% (n = 6, P < 0.05) at 1 Hz, the degree increased to 44% +/- 5% (n = 6, P < 0.01) at 3 Hz. 4) l-THP delayed half-recovery time of Ca2+ channel recovery from inactivity from (94 +/- 39) ms to (170 +/- 42) ms(n = 6, P < 0.01).


CONCLUSIONS
l-THP has a moderate inhibitory effect on L-Ca2+ current.
Huang
K
K
Department of Cardiology, Cardiovascular Disease Institute, Union Hospital. cjhuang@public.wuhan.cngb.com
Dai
G Z
GZ
Li
X H
XH
Fan
Q
Q
Cheng
L
L
Feng
Y B
YB
Xia
G J
GJ
Yao
W X
WX
D000818:Animals; D001600:Berberine Alkaloids / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects*; D005260:Female; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology; D008297:Male; D009206:Myocardium / Q000166:cytology*
D001600:Berberine Alkaloids; D002121:Calcium Channel Blockers; D015220:Calcium Channels; C014215:tetrahydropalmatine