Changes of [Ca2+] in the t-tubule lumen during activity may modulate the inotropic state of rat cardiac ventricular myocytes
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| Year of publication | 2004 |
| Type | Conference abstract |
| MU Faculty or unit | |
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| Description | The majority of trans-sarcolemmal Ca2+ flux occurs across the t-tubule membrane, which therefore plays a key role in cardiac excitation-contraction coupling; however Ca2+ within the t-tubules does not equilibrate instantaneously with the bulk extracellular solution. Thus, during activity, changes in [Ca2+] may occur within the t-tubule lumen, which would, in turn, alter trans-sarcolemmal Ca2+ flux. To test this hypothesis, we used a computer model of rat ventricular myocyte including a t-tubular system. The action potentials in the two membranes were not significantly different, reflecting the electrical coupling of the two compartments. However, [Ca2+] within the t-tubule lumen decreased on each stimulus, and decreased cumulatively, until reaching a new dynamic steady state, with increasing stimulation rate. These data suggest that activity-dependent depletion of Ca2+ within the t-tubule lumen, adjacent to the trans-sarcolemmal Ca2+ flux pathways, decreases the Ca load, and hence lowers the inotropic status, of ventricular myocytes. |
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