| Literature DB >> 10523412 |
J I Goldhaber1, S T Lamp, D O Walter, A Garfinkel, G H Fukumoto, J N Weiss.
Abstract
1. To determine whether Na+-Ca2+ exchange modulates Ca2+ sparks, we studied enzymatically isolated patch clamped rat ventricular myocytes loaded with the Ca2+-sensitive indicator fluo-3, using confocal microscopy at 20-22 C. Two-dimensional images of Ca2+ sparks were recorded at 240 Hz using a laser scanning confocal microscope, allowing observation of a large area of the cell (820 microm2) at one time. 2. At a holding potential of -75 mV, spontaneous sparks were infrequent. Removal of extracellular Na+ for 520 ms, which in the absence of pipette Na+ should block Na+-Ca2+ exchange bidirectionally, was associated with a fourfold increase in spark frequency, without a significant change in cytoplasmic [Ca2+], sarcoplasmic reticulum (SR) Ca2+ content, or spark intensity, size or time course. 3. These findings are consistent with a model of excitation-contraction coupling in which Na+-Ca2+ exchange locally regulates the resting Ca2+ concentration in the diadic cleft (T-tubule-SR junction), thereby modulating the threshold for triggering Ca2+ sparks.Entities:
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Year: 1999 PMID： 10523412 PMCID： PMC2269602 DOI： 10.1111/j.1469-7793.1999.00431.x
Source DB: PubMed Journal: J Physiol ISSN： 0022-3751 Impact factor: 5.182