Open AccessEffect of osmotic stress on spontaneous calcium sparks in rat ventricular myocytes
Author(s) -
XIE Hong,
ZHU Peihong
Publication year - 2006
Publication title -
acta pharmacologica sinica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.514
H-Index - 90
eISSN - 1745-7254
pISSN - 1671-4083
DOI - 10.1111/j.1745-7254.2006.00371.x
Subject(s) - myocyte , osmotic concentration , tonicity , ryanodine receptor , osmotic shock , calcium , biophysics , medicine , chemistry , endoplasmic reticulum , endocrinology , osmotic pressure , dextran , biology , biochemistry , gene
Aim: To study whether the volume of cardiomyocytes and their functions would change under severe pathological conditions or osmotic stress. To clarify the role of ryanodine receptors/calcium release channels (RyRs) in the functional change, the effect of osmotic stress on spontaneous Ca 2+ sparks in rat ventricular myocytes was investigated. Methods: A laser scanning confocal microscope was used to detect spontaneous Ca2+ sparks of intact or saponin permeabilized myocytes loaded with Fluo‐4. High and low tonicity was obtained by adding sucrose and reducing NaCl concentration in the external medium, respectively. Results: In intact myocytes the frequency of Ca 2+ sparks was increased and decreased by hyperosmotic (1.5 T) and hyposmotic (0.6 T) exposure, respectively. In addition, hyperosmotic exposure increased the temporal parameters and decreased the spatial parameter of Ca 2+ sparks, while opposite changes occurred with hyposmotic exposure. The spatio‐temporal properties of Ca 2+ sparks were slightly affected by altering [K + ] i (50‐200 mmol/L) in saponin permeabilized myocytes in the presence of 8% dextran. It was observed that the spatio‐temporal parameters of the Ca 2+ sparks in permeabilized myocytes were dose‐dependently altered by dextran. The propagating velocity of Ca 2+ waves in intact and permeabilized myocyte was also affected by osmotic pressure or dextran. Conclusion: The effect of osmotic stress on the frequency of spontaneous Ca 2+ sparks might be ascribed to the change of myoplasmic Ca 2+ and Ca 2+ content in the sarcoplasmic reticulum, while the effect on the spatio‐temporal properties is caused by the alteration of Ca 2+ diffusion mainly resulting from the morphological change of the myocytes.