Direct Measurement of Sarcoplasmic Reticulum Calcium Content Following Isoproterenol or Caffeine Treatment

1997 ◽  
Vol 3 (S2) ◽  
pp. 919-920
Author(s):  
Wendy E. Sweet ◽  
Christine S. Moravec
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Calcium Release ◽  
Calcium Influx ◽  
Calcium Content ◽  
Storage Site ◽  
Calcium Store ◽  
Indirect Methods ◽  
Β Receptor ◽  
Sarcoplasmic Reticulum Calcium

The major storage site for calcium in cardiac muscle is the sarcoplasmic reticulum (SR). It has been shown using indirect methods that the amount of calcium stored in the SR can be altered by various agonists and anesthetics. The only technique to date which directly quantifies the amount of calcium in the SR is Electron Probe Microanalysis (EPMA). Using EPMA, an accurate measurement of the size of the SR calcium store can be made following treatments with known agonists.Isoproterenol (ISO) causes an increased inotropic response in cardiac muscle via the (3-adrenergic pathway. When ISO binds to the (β-receptor on the plasma membrane, it causes the activation of Protein Kinase A (PKA) through a cascade of events. PKA phosphorylates the sarcolemmal calcium channels causing an increase in the rate of calcium influx. PKA also phosphorylates Tnl, which sensitizes the myofilaments to calcium, thereby increasing the rate of calcium release from the myofilaments.

scholarly journals What is the purpose of the large sarcolemmal calcium flux on each heartbeat?

2009 ◽  
Vol 297 (2) ◽  
pp. H493-H494 ◽  
Author(s):  
D. A. Eisner ◽  
A. W. Trafford
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Calcium Release ◽  
Calcium Influx ◽  
Calcium Content ◽  
Significant Fraction ◽  
Alternative Strategy ◽  
Calcium Flux ◽  
Rapid Changes ◽  
Inotropic Responses

In cardiac muscle, although most of the calcium that activates contraction comes from the sarcoplasmic reticulum (SR), a significant fraction (up to 30%, depending on the species) enters from outside the cell and is then pumped out at the end of systole. Although some of this calcium influx is required to trigger calcium release from the SR, the bulk serves to reload the cell (and thence the SR) with calcium to replace the calcium that is pumped out of the cell. An alternative strategy would be for the heart to have a much smaller calcium influx balancing a smaller efflux. We demonstrate that this would result in a slowing of inotropic responses due to changes of SR calcium content. We conclude that the large sarcolemmal calcium fluxes facilitate rapid changes of contractility.

scholarly journals Protein Phosphatases Decrease Sarcoplasmic Reticulum Calcium Content by Stimulating Calcium Release in Cardiac Myocytes

2003 ◽  
Vol 552 (1) ◽  
pp. 109-118 ◽  
Author(s):  
Dmitry Terentyev ◽  
Serge Viatchenko‐Karpinski ◽  
Inna Gyorke ◽  
Radmila Terentyeva ◽  
Sandor Gyorke
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Myocytes ◽  
Calcium Release ◽  
Protein Phosphatases ◽  
Calcium Content ◽  
Sarcoplasmic Reticulum Calcium
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