Contribution of spontaneous L-type Ca2+ channel activation to the genesis of Ca2+ sparks in resting cardiac myocytes.
Ca2+ sparks are the elementary events of intracellular Ca2+ release from the sarcoplasmic reticulum in cardiac myocytes. In order to investigate whether spontaneous L-type Ca2+ channel activation contributes to the genesis of spontaneous Ca2+ sparks, we used confocal laser scanning microscopy and fluo-4 to visualize local Ca2+ sparks in intact rat ventricular myocytes. In the presence of 0.2 mmol/L CdCl2 which inhibits spontaneous L-type Ca2+ channel activation, the rate of occurrence of spontaneous Ca2+ sparks was halved from 4.20 to 2.04 events/(100 microm x s), with temporal and spatial properties of individual Ca2+ sparks unchanged. Analysis of the Cd2+-sensitive spark production revealed an open probability of approximately 10(-5) for L-type channels at the rest membrane potentials (-80 mV). Thus, infrequent and stochastic openings of sarcolemmal L-type Ca2+ channels in resting heart cells contribute significantly to the production of spontaneous Ca2+ sparks.
Guangqin
Zhang
Z
National Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing 100871, China.
Yu
Fu
F
Dongmei
Yang
Y
Xuemei
Hao
H
Shuhua
Bai
B
Yiqun
Tang
T
Lakatta
Edward G
EG
Caihong
Wu
W
Heping
Cheng
C
D000814:Aniline Compounds; D000818:Animals; D019256:Cadmium Chloride / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D007399:Interphase; D008564:Membrane Potentials; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014966:Xanthenes
D000814:Aniline Compounds; D020746:Calcium Channels, L-Type; C409648:Fluo 4; D005456:Fluorescent Dyes; D014966:Xanthenes; D019256:Cadmium Chloride