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Ca efflux via the sarcolemmal Ca ATPase occurs only in the t-tubules of rat ventricular myocytes
- Source :
-
Journal of Molecular & Cellular Cardiology . Jan2011, Vol. 50 Issue 1, p187-193. 7p. - Publication Year :
- 2011
-
Abstract
- Abstract: The transverse (t-) tubule network is an important site for Ca influx and release during excitation-contraction coupling in cardiac ventricular myocytes; however, its role in Ca extrusion is less clear. The present study was designed to investigate the relative contributions of Ca extrusion pathways across the t-tubule and surface membranes. Ventricular myocytes were isolated from the hearts of adult male Wistar rats and detubulated using formamide. Intracellular Ca was monitored using fluo-3 and confocal microscopy. Caffeine (20mmol/L) was used to induce SR Ca release; carboxyeosin (20μmol/L) and nickel (10mmol/L) were used to inhibit the sarcolemmal Ca ATPase and Na/Ca exchanger (NCX) respectively. Carboxyeosin decreased the rate constant of decay of the caffeine-induced Ca transient in control cells, but had no effect in detubulated cells, suggesting that Ca extrusion via the Ca ATPase occurs only across the t-tubule membrane. However nickel decreased the rate constant of the caffeine-induced Ca transient in control and detubulated cells, although its effect was greater in control cells, suggesting that Ca extrusion via NCX occurs across the surface and t-tubule membranes. The PKA inhibitor H-89 (10μmol/L) was used to investigate the role of basal PKA activity in Ca extrusion; H-89 appeared to have no effect on Ca extrusion via the Ca ATPase, but reduced Ca extrusion via NCX at the t-tubules but not the surface membrane. Thus it appears that Ca extrusion via the sarcolemmal Ca ATPase occurs only at the t-tubules, and is not regulated by basal PKA activity, while Ca extrusion via NCX occurs across both the surface and t-tubule membranes, but predominantly across the t-tubule membrane due, in part, to localised stimulation of NCX by PKA at the t-tubules. This may be important in heart disease, in which changes in t-tubule structure and protein phosphorylation occur. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00222828
- Volume :
- 50
- Issue :
- 1
- Database :
- Academic Search Index
- Journal :
- Journal of Molecular & Cellular Cardiology
- Publication Type :
- Academic Journal
- Accession number :
- 57293776
- Full Text :
- https://doi.org/10.1016/j.yjmcc.2010.10.012