Spontaneous Ca2+ transients in rat pulmonary vein cardiomyocytes are increased in frequency and become more synchronous following electrical stimulation

Henry, A. D., MacQuaide, N. , Burton, F.L., Rankin, A.C., Rowan, E.G. and Drummond, R.M. (2018) Spontaneous Ca2+ transients in rat pulmonary vein cardiomyocytes are increased in frequency and become more synchronous following electrical stimulation. Cell calcium, 76, pp. 36-47. (doi: 10.1016/j.ceca.2018.09.001) (PMID:30253263)

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Abstract

The pulmonary veins have an external sleeve of cardiomyocytes that are a widely recognised source of ectopic electrical activity that can lead to atrial fibrillation. Although the mechanisms behind this activity are currently unknown, changes in intracellular calcium (Ca2+) signalling are purported to play a role. Therefore, the intracellular Ca2+ concentration was monitored in the pulmonary vein using fluo-4 and epifluorescence microscopy. Electrical field stimulation evoked a synchronous rise in Ca2+ in neighbouring cardiomyocytes; asynchronous spontaneous Ca2+ transients between electrical stimuli were also present. Immediately following termination of electrical field stimulation at 3 Hz or greater, the frequency of the spontaneous Ca2+ transients was increased from 0.45 ± 0.06 Hz under basal conditions to between 0.59 ± 0.05 and 0.65 ± 0.06 Hz (P < 0.001). Increasing the extracellular Ca2+ concentration enhanced this effect, with the frequency of spontaneous Ca2+ transients increasing from 0.45 ± 0.05 Hz to between 0.75 ± 0.06 and 0.94 ± 0.09 Hz after electrical stimulation at 3 to 9 Hz (P < 0.001), and this was accompanied by a significant increase in the velocity of Ca2+ transients that manifested as waves. Moreover, in the presence of high extracellular Ca2+, the spontaneous Ca2+ transients occurred more synchronously in the initial few seconds following electrical stimulation. The ryanodine receptors, which are the source of spontaneous Ca2+ transients in pulmonary vein cardiomyocytes, were found to be arranged in a striated pattern in the cell interior, as well as along the periphery of cell. Furthermore, labelling the sarcolemma with di-4-ANEPPS showed that over 90% of pulmonary vein cardiomyocytes possessed T-tubules. These findings demonstrate that the frequency of spontaneous Ca2+ transients in the rat pulmonary vein are increased following higher rates of electrical stimulation and increasing the extracellular Ca2+ concentration.

Item Type:Articles
Additional Information:This work was funded by a British Heart Foundation studentship (FS/11/6/28641).
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Burton, Dr Francis and MacQuaide, Dr Niall and Rankin, Mrs Aileen
Authors: Henry, A. D., MacQuaide, N., Burton, F.L., Rankin, A.C., Rowan, E.G., and Drummond, R.M.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
Journal Name:Cell calcium
Publisher:Elsevier
ISSN:0143-4160
ISSN (Online):1532-1991
Published Online:16 September 2018

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