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 mum (.) s), with temporal and spatial properties of individual Ca2+ sparks unchanged. Analysis of the Cd2+-sensitive spark production revealed an open probability of similar to10(-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.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000188951300005&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701BiologySCI(E)1131-374