Effect of osmotic stress on spontaneous calcium sparks in rat ventricular myocytes

• Published in: Acta pharmacologica Sinica Vol. 27; no. 7; pp. 877 - 887
• Main Authors: XIE, Hong, ZHU, Pei‐hong
• Format: Journal Article
• Language: English
• Published: Melbourne, Australia Blackwell Publishing Asia 01.07.2006; Nature Publishing Group
• Subjects: Animals; Aspartic Acid - pharmacology; Caffeine - pharmacology; Calcium - metabolism; Calcium Signaling - physiology; calcium sparks; Cell Separation; Dextrans - administration & dosage; Dextrans - pharmacology; Dose-Response Relationship, Drug; Heart Ventricles - cytology; Microscopy, Confocal; Myocytes, Cardiac - cytology; Myocytes, Cardiac - physiology; Osmotic Pressure; osmotic stress; rat ventricular myocytes; Rats; Rats, Sprague-Dawley; Sarcoplasmic Reticulum - metabolism; 心肌细胞; 渗透应力; 生理学; 钙离子
• ISSN: 1671-4083; 1745-7254
• DOI: 10.1111/j.1745-7254.2006.00371.x

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 Ca^2＋ sparks of intact or saponin permeabilized myocytes loaded with Fluo-4. High and low tonicity was obtained by adding sucrose and reducing NaCI 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.