Affiliation:
1. From the School of Biomedical Sciences, University of Leeds, Leeds, UK.
Abstract
Detubulation of rat ventricular myocytes has been used to investigate the role of the t-tubules in Ca
2+
cycling during excitation-contraction coupling in rat ventricular myocytes. Ca
2+
was monitored using fluo-3 and confocal microscopy. In control myocytes, electrical stimulation caused a spatially uniform increase in intracellular [Ca
2+
] across the cell width. After detubulation, [Ca
2+
] 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
2+
]; 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
2+
] as Ca
2+
was extruded from the cell; this rise was significantly smaller in detubulated cells, and the remaining increase was blocked by the sarcolemmal Ca
2+
ATPase inhibitor carboxyeosin. The treatment used to produce detubulation had no significant effect on Ca
2+
efflux in atrial cells, which lack t-tubules. Detubulation of ventricular myocytes also resulted in loss of Na
+
-Ca
2+
exchange current, although the density of the fast Na
+
current was unaltered. It is concluded that Na
+
-Ca
2+
exchange function, and hence Ca
2+
efflux by this mechanism, is concentrated in the t-tubules, and that the concentration of Ca
2+
flux pathways in the t-tubules is important in producing a uniform increase in intracellular Ca
2+
on stimulation.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine,Physiology
Cited by
96 articles.
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