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


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 Ca2+ and 5 mar ATP elicited regular waves of Ca2+ (approximately every 5 s) due to spontaneous release of Ca2+ from the sarcoplasmic reticulum (SR).

2. An approximately linear relationship was noted between Ca2+ wave velocity(v) 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-1 µM-1 (n = 78).

3. Reduction of [ATP] in the bathing solution to 0.5 and 0.2 mM ATP progressively decreased Ca2+ wave frequency and propagation velocity while increasing the amplitude. The changes in Ca2+ 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 [Ca2+] during a Ca2+ wave was slowed suggesting a lowered rate of Ca2+ re-uptake by the SR Ca2+ pump.

4. Reduction of [ATP] to 0.1. mM abolished Ca2+ 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).

5. Rapid application of caffeine (10 mM) was used to assess the SR Ca2+ content. This showed that SR Ca2+ increased as [ATP] was reduced or [tetracaine] was increased. The highest SR Ca2+ content was observed after perfusion with 0.1 mM ATP, which was 245 ± 15 % of control values.

6. Returning [ATP] from 0.1 mM to 5 mM caused a burst of high frequency, large amplitude Ca2+ waves. But recovery after incubation with 300 muM tetracaine resulted in SR Ca2+ release with no coherent wave pattern. The reason for this discrepancy is discussed.

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 > Institute of Cardiovascular and Medical Sciences
Journal Name:Journal of Physiology
ISSN (Online):1469-7793
Published Online:05 August 2004

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