The effect of tetracaine on supontaneous Ca 2+ release and sarcoplasmic reticulum calcium content in rat ventricular myocytes

• Published in: The Journal of physiology Vol. 502; no. 3; pp. 471 - 479
• Main Authors: Overend, C. L., Eisner, D. A., O'Neill, S. C.
• Format: Journal Article
• Language: English
• Published: 01.08.1997
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1111/j.1469-7793.1997.471bj.x

The effects of tetracaine were studied on voltage‐clamped rat ventricular myocytes, which exhibited Ca 2+ overload as identified by supontaneous Ca 2+ release from the sarcoplasmic reticulum (SR) as shown by the associated contractions. This Ca 2+ release was initially abolished by tetracaine before returning at a lower frequency, but greater amplitude, than the control. On removal of tetracaine, there was a burst of supontaneous Ca 2+ release activity. All these effects were dose dependent, from 25 to 200 μ m tetracaine. The supontaneous Ca 2+ release activated an inward Na + –Ca 2+ exchange current as Ca 2+ was pumped out of the cell. The integral of this current (i.e. the Ca 2+ efflux) was increased in the presence of tetracaine. The calcium efflux per unit time was unaffected by tetracaine. The SR Ca 2+ content was increased by tetracaine, as shown by the integral of the caffeine‐evoked Na + –Ca 2+ exchange current. The increase of SR Ca 2+ content was equal to the extra Ca 2+ lost from the cell during the burst on removal of tetracaine, and to estimates of the extra calcium gained over the quiescent period following addition of tetracaine. It is concluded that partial inhibition of calcium‐induced calcium release increases SR Ca 2+ content. In the steady state, cell Ca 2+ balance is maintained as the lower frequency of supontaneous release (that activates efflux) is compensated for by their greater size.