A comparison of the effects of ATP and tetracaine on spontaneous Ca2+ release from rat permeabilised cardiac myocytes

Smith, G.L. and ONeill, S.C. (2001) A comparison of the effects of ATP and tetracaine on spontaneous Ca2+ release from rat permeabilised cardiac myocytes. Journal of Physiology, 534(1), pp. 37-47. (doi: 10.1111/j.1469-7793.2001.00037.x)

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Publisher's URL: http://dx.doi.org/10.1111/j.1469-7793.2001.00037.x


<p>1. Fluo-3 fluorescence measurements were made in isolated beta -escin permeablised rat cardiac myocytes using confocal microscopy. Perfusion of a mock intracellular solution containing 0.22-0.23 µmM Ca<sup>2+</sup> and 5 mar ATP elicited regular waves of Ca<sup>2+</sup> (approximately every 5 s) due to spontaneous release of Ca<sup>2+</sup> from the sarcoplasmic reticulum (SR).</p> <p>2. An approximately linear relationship was noted between Ca<sup>2+</sup> wave velocity(<i>v</i>) and amplitude (σ). Under the control conditions the ratio of velocity to amplitude (nu/sigma) varied little and was 99.8 ± 2.5 m s<sup>-1</sup> µM<sup>-1</sup> (n = 78).</p> <p>3. Reduction of [ATP] in the bathing solution to 0.5 and 0.2 mM ATP progressively decreased Ca<sup>2+</sup> wave frequency and propagation velocity while increasing the amplitude. The changes in Ca<sup>2+</sup> wave characteristics in 0.5 MM ATP were similar to those observed during perfusion with 50 µM tetracaine. In 0.2 mM ATP the decline of [Ca<sup>2+</sup>] during a Ca<sup>2+</sup> wave was slowed suggesting a lowered rate of Ca<sup>2+</sup> re-uptake by the SR Ca<sup>2+</sup> pump.</p> <p>4. Reduction of [ATP] to 0.1. mM abolished Ca<sup>2+</sup> waves after 15-20 s. Returning the [ATP] to 5 mM caused a burst of high frequency and large amplitude waves. Mean velocity of the first wave on returning to 5 mar ATP st-as larger than normal but the v/μ value was 32 ± 6 % of control (n = B). In the similar burst on removal of 100 muM tetracaine nu/sigma was higher than control (166 ± 9%, n = 6).</p> <p>5. Rapid application of caffeine (10 mM) was used to assess the SR Ca<sup>2+</sup> content. This showed that SR Ca<sup>2+</sup> increased as [ATP] was reduced or [tetracaine] was increased. The highest SR Ca<sup>2+</sup> content was observed after perfusion with 0.1 mM ATP, which was 245 ± 15 % of control values.</p> <p>6. Returning [ATP] from 0.1 mM to 5 mM caused a burst of high frequency, large amplitude Ca<sup>2+</sup> waves. But recovery after incubation with 300 muM tetracaine resulted in SR Ca<sup>2+</sup> release with no coherent wave pattern. The reason for this discrepancy is discussed.</p>

Item Type:Articles
Glasgow Author(s) Enlighten ID:Smith, Professor Godfrey
Authors: Smith, G.L., and ONeill, S.C.
College/School:College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health
Journal Name:Journal of Physiology
ISSN (Online):1469-7793
Published Online:05 August 2004

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