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A comparison of the effects of ATP and tetracaine on spontaneous Ca 2+ release from rat permeabilised cardiac myocytes
Author(s) -
Smith G. L.,
O'Neill S. C.
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.00037.x
Subject(s) - tetracaine , chemistry , biophysics , endoplasmic reticulum , calcium , perfusion , myocyte , extracellular , medicine , biochemistry , anesthesia , biology , organic chemistry , lidocaine
1 Fluo‐3 fluorescence measurements were made in isolated β‐escin permeablised rat cardiac myocytes using confocal microscopy. Perfusion of a mock intracellular solution containing 0.22‐0.23 μ m Ca 2+ and 5 m m ATP elicited regular waves of Ca 2+ (approximately every 5 s) due to spontaneous release of Ca 2+ from the sarcoplasmic reticulum (SR). 2 An approximately linear relationship was noted between Ca 2+ wave velocity ( v) and amplitude (σ). Under the control conditions the ratio of velocity to amplitude ( v /σ) varied little and was 99.8 ± 2.5 m s −1 μ m −1 (n = 78). 3 Reduction of [ATP] in the bathing solution to 0.5 and 0.2 m m ATP progressively decreased Ca 2+ wave frequency and propagation velocity while increasing the amplitude. The changes in Ca 2+ wave characteristics in 0.5 m m ATP were similar to those observed during perfusion with 50 μ m tetracaine. In 0.2 m m ATP the decline of [Ca 2+ ] during a Ca 2+ wave was slowed suggesting a lowered rate of Ca 2+ re‐uptake by the SR Ca 2+ pump. 4 Reduction of [ATP] to 0.1 m m abolished Ca 2+ waves after 15‐20 s. Returning the [ATP] to 5 m m caused a burst of high frequency and large amplitude waves. Mean velocity of the first wave on returning to 5 m m ATP was larger than normal but the v /σ value was 32 ± 6 % of control (n = 6). In the similar burst on removal of 100 μ m tetracaine v /σ was higher than control (166 ± 9 %, n = 6). 5 Rapid application of caffeine (10 m m ) was used to assess the SR Ca 2+ content. This showed that SR Ca 2+ increased as [ATP] was reduced or [tetracaine] was increased. The highest SR Ca 2+ content was observed after perfusion with 0.1 m m ATP, which was 245 ± 15 % of control values. 6 Returning [ATP] from 0.1 m m to 5 m m caused a burst of high frequency, large amplitude Ca 2+ waves. But recovery after incubation with 300 μ m tetracaine resulted in SR Ca 2+ release with no coherent wave pattern. The reason for this discrepancy is discussed.