Sarcoplasmic Reticulum Calcium Release Channels in Ventricles of Older Adult Hamsters

2006 ◽  
Vol 25 (1) ◽  
pp. 107-113 ◽  
Author(s):  
Peter A. Nicholl ◽  
Susan E. Howlett
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Older Adult ◽  
Binding Sites ◽  
Calcium Release ◽  
Ryanodine Receptors ◽  
Calcium Release Channels ◽  
Site Density ◽  
Age Related ◽  
Sarcoplasmic Reticulum Calcium ◽  
Age Related Changes

ABSTRACTWhether the density of sarcoplasmic reticulum (SR) calcium release channels / ryanodine receptors in the heart declines with age is not clear. We investigated age-related changes in the density of «3H»-ryanodine receptors in crude ventricular homogenates, which contained all ligand binding sites in heart and in isolated junctional SR membranes. Experiments utilized young (120 days) and older adult (300 days) hamsters. «3H»-ryanodine binding site density did not change with age in crude homogenate preparations, although total heart protein concentration increased significantly with age. In contrast, the density of «3H»-ryanodine binding sites decreased markedly in heavy SR membranes purified from older hearts. These results show that demonstration of age-related changes in cardiac ryanodine receptor density depends upon the preparation used. Furthermore, the increase in total ventricular protein with age suggests that normalization of data by membrane protein should be used with caution in studies of aging heart.

How Many Ryanodine Binding Sites Are Involved in Caffeine Induced Calcium Release from Sarcoplasmic Reticulum Terminal Cysternae Vesicles?

1992 ◽  
Vol 47 (1-2) ◽  
pp. 136-147 ◽  
Author(s):  
Wilhelm Hasselbach ◽  
Andrea Migala
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Channel ◽  
Binding Sites ◽  
Calcium Release ◽  
Initial Rate ◽  
Ryanodine Receptors ◽  
Stoichiometric Composition ◽  
Calcium Release Channels ◽  
Equilibrium Binding ◽  
Reported Data

Abstract The inhibition by ryanodine of caffeine induced calcium release from actively loaded heavy sarcoplasmic vesicles has been studied in order to analyse the relation between the occupancy of the vesicular calcium release channels by ryanodine and channel function. Ryanodine binding was monitored with [3H]ryanodine under ionic conditions favouring the establishment of binding equilibrium. Binding follows 1 : 1 stoichiometry yielding dissociations constants between 7 - 12 nᴍ and 12-15 pmol ryanodine/mg vesicular protein as maximum number of ryanodine binding sites. When ryanodine labeling was monitored by measuring the decline of the amplitude of caffeine induced calcium release 50% inhibition occurred at a free ryanodine concentration of 1 nM. At this concentration less than 10% of the available ryanodine binding sites are occupied. Caffeine induced calcium release is completely abolished when 3 pmol ryanodine/mg have reacted. A corresponding divergence between ryanodine binding and its effect on caffeine induced calcium release was observed when the initial rate of ryanodine binding was measured either by labeling the vesicles with [3H]ryanodine or by following the decline with time of caffeine induced calcium release. Caffein induced calcium release declines four times faster than the fraction of unoccupied ryanodine binding sites, k = 4.3 x 104 ᴍ-1 s-1 versus 1.2 x 104 ᴍ-1 s-1. The observed interrelation between the occupation of ryanodine binding sites and its effect on caffeine induced calcium release indicates that the caffeine sensitive calcium channel functions as an assembly of at least 4 ryanodine binding sites whereby the occupation of one site suffices to abolish calcium release. The stoichiometric composition appears to be not fixed but might change according to the size of the fraction of ryanodine receptors exhibiting caffeine sensitivity. The reported data were evaluated according to the algorithm derived by H. Asai and M. F. Morales, J. Biol. Chem. 4, 830-838 (1965) for the activity of a macromolecule and the extent of an inhibiting reaction.

Cyclic ADP-ribose stimulates sarcoplasmic reticulum calcium release in porcine coronary artery smooth muscle

1996 ◽  
Vol 270 (2) ◽  
pp. H801-H806 ◽  
Author(s):  
M. S. Kannan ◽  
A. M. Fenton ◽  
Y. S. Prakash ◽  
G. C. Sieck
Keyword(s):  
Smooth Muscle ◽  
Coronary Artery ◽  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Direct Evidence ◽  
Ryanodine Receptors ◽  
Porcine Coronary Artery ◽  
Inositol 1 ◽  
Cyclic Adp Ribose ◽  
Sarcoplasmic Reticulum Calcium

Cyclic ADP-ribose (cADPR) was shown to induce calcium release from the endoplasmic reticulum via ryanodine-sensitive pathways. In smooth muscle, two pathways for calcium release from the sarcoplasmic reticulum (SR) have been previously demonstrated: D-myo-inositol 1, 4, 5-trisphosphate-gated and ryanodine-gated. However, evidence for cADPR as a regulator for SR Ca2+ release in smooth muscle is lacking. We used permeabilized porcine coronary artery smooth muscle cells to directly examine the stimulation of SR Ca2+ release by cADPR. The results provide direct evidence that cADPR stimulates SR Ca2+ release and that this response is not inhibited by heparin, by depletion of the caffeine-sensitive Ca2+ pool, or by blockade or ryanodine receptors. These results indicate a novel mechanism for Ca2+ release from the SR of vascular smooth muscle.

Sarcoplasmic Reticulum Calcium Release Channels

2012 ◽  
pp. 1725-1725
Author(s):  
Brian R. Dempsey ◽  
Anne C. Rintala-Dempsey ◽  
Gary S. Shaw ◽  
Yuan Xiao Zhu ◽  
A. Keith Stewart ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Calcium Release Channels ◽  
Sarcoplasmic Reticulum Calcium
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