Quantification of calcium release from the sarcoplasmic reticulum in rainbow trout atrial myocytes

Leif Hove-Madsen, Anna Llach, Lluis Tort

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    31 Citations (Scopus)


    Using the whole-cell configuration of the patch-clamp technique, we quantified calcium release from the sarcoplasmic reticulum (SR) elicited by short depolarization pulses before and after clearance of the SR Ca2+ content with 10 mM caffeine (CAF). With a loaded SR, the first detectable contraction occurred with a pulse duration of 5 ms. CAF exposure increased this pulse duration to 85 ms and slowed the inactivation of the Ca2+ current (I(Ca)). Repolarization of the cell to -80 mV after a short depolarization elicited a tail current that was attenuated markedly after CAF exposure. The difference between the charge carried by the tail currents obtained before and after CAF exposure was taken as a measure of the Ca2+ released from the SR. SR Ca2+ release increased with increasing SR Ca2+ load over the range of loads examined. In contrast, SR Ca2+ release reached a maximum when the duration of the preceding depolarization exceeded 10 ms. Maximal Ca2+ release was 1.64 amol/pF or 62 μM and elicited a contraction that was 40±6% of the amplitude of a normal contraction. This release could account for 48±10% of the total Ca2+ required to activate contraction but only a few percent of the CAF-releasable Ca2+. Thus, contrary to the general view of excitation-contraction coupling in lower vertebrates, SR Ca2+ release in trout atrial myocytes may account for up to 50% of the total Ca2+ transient at room temperature.
    Original languageEnglish
    Pages (from-to)545-552
    JournalPflugers Archiv European Journal of Physiology
    Publication statusPublished - 15 Sep 1999


    • Caffeine
    • Calcium current
    • Contraction
    • Contraction coupling
    • Excitation
    • Heart
    • Na -Ca exchange + 2+
    • Ryanodine


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