Simultaneous recording of Indo‐1 flourescence and Na+/Ca2+ exchange current reveals two components of Ca2+‐release from sarcoplasmic reticulum of cardiac atrial myocytes
Open Access
- 26 November 1990
- journal article
- research article
- Published by Wiley in FEBS Letters
- Vol. 275 (1-2), 181-184
- https://doi.org/10.1016/0014-5793(90)81467-3
Abstract
Simultaneous measurements of intracellular Ca2+-concentration ([Ca2+]1) using Indo-1 and the current generated by electrogenic Na1/Ca2+-exchange (INa??? have been performed on atrial myocytes from hearts of adult guinea-pigs. Whereas the flourescence-measurements provide information on global[Ca2+]i, INa??? which is a linear function of Ca2+-concentration, indicates subsarcolemmal [Ca2+]. Under conditions in which intracellular Ca2+-transients due to Ca2+-release from the sarcoplasmic reticulum (SR) have been artificially slowed, a deviation between the two different Ca2+-signals can be found. During onset of release signals Ca2+-concentration seen by the membrane is higher than global [Ca2+]1. Our results provide evidence that in atrial myocytes, lacking a T-system, Ca2+-release occurs first from a subsarcolemmal compartment of the SR. The resulting Ca2+-transient serves to trigger Ca2+-release from deeper SR-compartments.Keywords
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