Smyrnias, Ioannis; Mair, Waltraud; Harzheim, Dagmar; Walker, Simon A.; Roderick, H. Llewelyn and Bootman, Martin D.
(2010).
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| DOI (Digital Object Identifier) Link: | http://dx.doi.org/doi:10.1016/j.ceca.2009.10.001 |
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Abstract
Narrow, tubular, inward projections of the sarcolemma ('T-tubules') are an established feature of adult mammalian ventricular myocytes that enables them to generate the whole-cell Ca2+ transients and produce coordinated contraction. Loss of T-tubules can occur during ageing and under pathological conditions, leading to altered cardiac excitation-contraction coupling. In contrast to adult ventricular cells, atrial myocytes do not generally express an extensive T-tubule system at any stage of development, and therefore rely on Ca2+ channels around their periphery for the induction of Ca2+ signalling and excitation-contraction coupling. Consequently, the characteristics of systolic Ca2+ signals in adult ventricular and atrial myocytes are temporally and spatially distinct. However, although atrial myocytes do not have the same regularly spaced convoluted T-tubule structures as adult ventricular cells, it has been suggested that a proportion of adult atrial cells have a more rudimentary tubule system. We examined the structure and function of these atrial tubules, and explored their impact on the initiation and recovery of Ca2+ signalling in electrically paced myocytes. The atrial responses were compared to those in adult ventricular cells that had intact T-tubules, or that had been chemically detubulated. We found that tubular structures were present in a significant minority of adult atrial myocytes, and were unlike the T-tubules in adult ventricular cells. In those cells where they were present, the atrial tubules significantly altered the on-set, amplitude, homogeneity and recovery of Ca2+ transients. The properties of adult atrial myocyte Ca2+ signals were different from those in adult ventricular cells, whether intact or detubulated. Excitation-contraction coupling in detubulated adult ventricular myocytes, therefore, does not approximate to atrial signalling, even though Ca2+ signals are initiated in the periphery of the cells in both of these situations. Furthermore, inotropic responses to endothelin-1 were entirely dependent on T-tubules in adult ventricular myocytes, but not in atrial cells. Our data reveal that that the T-tubules in atrial cells impart significant functional properties, but loss of these tubular membranes does not affect Ca2+ signalling as dramatically as detubulation in ventricular myocytes.
| Item Type: | Journal Article |
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| Copyright Holders: | 2010 Elsevier |
| ISSN: | 0143-4160 |
| Academic Unit/Department: | Science > Life, Health and Chemical Sciences |
| Item ID: | 35104 |
| Depositing User: | Martin Bootman |
| Date Deposited: | 20 Nov 2012 11:44 |
| Last Modified: | 20 Nov 2012 11:44 |
| URI: | http://oro.open.ac.uk/id/eprint/35104 |
Available Versions of this Item
- Comparison of the T-tubule system in adult rat ventricular and atrial myocytes, and its role in excitation-contraction coupling and inotropic stimulation. (deposited 20 Nov 2012 11:44) [Currently Displayed]
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