-Ca Exchange Activity Is Localized in the T-Tubules of Rat Ventricular Myocytes

Abstract

Detubulation of rat ventricular myocytes has been used to investigate the role of the t-tubules in Ca cycling during excitation-contraction coupling in rat ventricular myocytes. Ca was monitored using fluo-3 and confocal microscopy. In control myocytes, electrical stimulation caused a spatially uniform increase in intracellular [Ca ] across the cell width. After detubulation, [Ca ] rose initially at the cell periphery and then propagated into the center of the cell. Application of caffeine to control myocytes resulted in a rapid and uniform increase of intracellular [Ca ]; the distribution and amplitude of this increase was the same in detubulated myocytes, although its decline was slower. On application of caffeine to control cells, there was a large, rapid, and transient rise in extracellular [Ca ] as Ca was extruded from the cell; this rise was significantly smaller in detubulated cells, and the remaining increase was blocked by the sarcolemmal Ca ATPase inhibitor carboxyeosin. The treatment used to produce detubulation had no significant effect on Ca efflux in atrial cells, which lack t-tubules. Detubulation of ventricular myocytes also resulted in loss of Na -Ca exchange current, although the density of the fast Na current was unaltered. It is concluded that Na -Ca exchange function, and hence Ca efflux by this mechanism, is concentrated in the t-tubules, and that the concentration of Ca flux pathways in the t-tubules is important in producing a uniform increase in intracellular Ca on stimulation. (Circ Res. 2002;91:315-322.)

5 Figures and Tables

Cite this paper

@inproceedings{Yang2002CaEA, title={-Ca Exchange Activity Is Localized in the T-Tubules of Rat Ventricular Myocytes}, author={Z. Yang}, year={2002} }