Quantitative exploration of T-tubular membrane parameters in a model of rat ventricular cardiomyocyte
| Authors | |
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| Year of publication | 2005 |
| Type | Article in Periodical |
| Magazine / Source | Journal of Molecular and Cellular Cardiology |
| MU Faculty or unit | |
| Citation | |
| Field | Physiology |
| Keywords | cardiac cell; tubular system; quantitative modelling |
| Description | Formamide-induced detubulation of rat ventricular cardiac myocytes causes an ~32% decrease of membrane capacitance (Despa et al, 2003). Detailed microscopic analysis of the transverse-axial tubular system (TATS) by Soeller and Cannel (1999) showed a mean tubule diameter of 255 nm, a mean segment length of 6.87 ľm, a tubule density of 0.3 ľm-2, fractional volume of 3.6% and TATS membrane area to cell volume ratio of 0.44 ľm2/ľm3. These parameters can be approximately respected when the fraction of the total sarcolemma within the TATS is 56%. To explore possible causes for this discrepancy we used a quantitative model of the rat ventricular myocyte that included a description of TATS. Two explanations were found that could account quantitatively for the discrepancy: (i) incomplete detubulation leaving electrical access to a large area of TATS membrane, due to the branched TATS network. The estimate of Despa et al. could be met if 42% of TATS remained accessible after detubulation. (ii) the specific membrane capacitance of TATS membrane is lower than that of the surface sarcolemma (set to 1 ľFcm-2). Such a difference may result from the different composition of the two membranes. To account for the discrepancy, the specific capacitance of the TATS membrane must be decreased to 0.37 ľF.cm-2. A combination of both explanations may contribute to the observed discrepancy, e.g. 15% TATS membrane area remaining accessible with specific capacitance of 0.47 ľF.cm-2. |
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