scholarly journals Release of Ca2+ from a non-mitochondrial store site in peritoneal macrophages treated with saponin by inositol 1,4,5-trisphosphate

1984 ◽  
Vol 223 (1) ◽  
pp. 229-236 ◽  
Author(s):  
M Hirata ◽  
E Suematsu ◽  
T Hashimoto ◽  
T Hamachi ◽  
T Koga
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Sarcoplasmic Reticulum ◽  
Inhibitory Effect ◽  
Peritoneal Macrophages ◽  
Erythrocyte Ghosts ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Intracellular Store ◽  
Inositol 1,4,5 Trisphosphate ◽  
Inside Out

The effects of inositol 1,4,5-trisphosphate, prepared from human erythrocyte ghosts, on Ca2+ release from intracellular store sites were studied in saponin-treated guinea pig peritoneal macrophages. Micromolar concentrations of inositol 1,4,5-trisphosphate released Ca2+ within 1 min from store sites which had accumulated Ca2+ in the presence of 10 mM-NaN3. In the presence of 10 mM-NaN3, the Ca2+ accumulated in the presence of oxalate was seen in the endoplasmic reticulum of saponin-treated macrophages by electron microscopy, indicating that the site of Ca2+ released by inositol 1,4,5-trisphosphate may be endoplasmic reticulum-like membranes. When the concentrations of free Ca2+ were over 3.5 × 10(-6) M, the release of Ca2+ by this agent was inhibited. This inhibition may be due to either the higher concentration of extra-vesicular free Ca2+ or the larger accumulation of Ca2+ into the store site or perhaps both effects. MgCl2 also had an inhibitory effect on the Ca2+ release. Inositol 1,4,5-trisphosphate also released Ca2+ from cardiac sarcoplasmic reticulum, but not from erythrocyte inside-out vesicles.

cADP-ribose releases Ca2+ from cardiac sarcoplasmic reticulum independently of ryanodine receptor

1997 ◽  
Vol 273 (3) ◽  
pp. H1082-H1089 ◽  
Author(s):  
P. Lahouratate ◽  
J. Guibert ◽  
J. F. Faivre
Keyword(s):  
Endoplasmic Reticulum ◽  
Sarcoplasmic Reticulum ◽  
Ryanodine Receptor ◽  
Sea Urchin ◽  
Calcium Release ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Consistent Effect ◽  
Cyclic Adp Ribose

Cyclic ADP-ribose (cADPR), an endogenous metabolite of beta-NAD+, activates Ca2+ release from endoplasmic reticulum in sea urchin eggs via the ryanodine receptor (RyR) pathway. A similar role has been proposed in cardiac sarcoplasmic reticulum (SR), although this remains controversial. We therefore investigated the ability of cADPR to induce Ca2+ release from canine cardiac SR microsomes using fluo 3 to monitor extravesicular Ca2+ concentration. We found that cADPR induced Ca2+ release in a concentration-dependent manner, whereas neither its precursor, NAD+, nor its metabolite, ADP-ribose, elicited a consistent effect. In addition, an additive effect on calcium release between cADPR and 9-Me-7-Br-eudistomin-D (MBED), an activator of RyR, was found as well as no cross-desensitization between cADPR and MBED. Specific blockers of the RyR did not abolish the cADPR-induced Ca2+ release. These results provide evidence for cADPR-induced Ca2+ release from dog cardiac SR via a novel mechanism which is independent of RyR activation.

scholarly journals THE SARCOPLASMIC RETICULUM IN MUSCLE CELLS OF AMBLYSTOMA LARVAE

1956 ◽  
Vol 2 (4) ◽  
pp. 163-170 ◽  
Author(s):  
Keith R. Porter
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Sarcoplasmic Reticulum ◽  
Constant Width ◽  
Muscle Cells ◽  
Cell Types ◽  
Thin Sections ◽  
System A ◽  
Structural Relationships ◽  
Complex Membrane

Electron microscopy of thin sections of muscle fibers in myotomes of Amblystoma larvae has revealed the presence of a complex, membrane-limited system of canaliculi and vesicles which form a lace-like reticulum around and among the myofibrils. This seems to correspond to the sarcoplasmic reticulum of the earlier light microscopists and the endoplasmic reticulum of other cell types. The elements constituting the reticulum are disposed in a pattern which bears a constant relation to the bands of the adjacent myofibrils and is therefore repeated in each sarcomere. At the H band the system is transversely continuous but not so at other levels. Longitudinally continuity is interrupted at the Z bands where large vesicles belonging to adjacent sarcomere segments of the system face off on opposite sides of the band. The opposing faces of these vesicles are flat and separated by a space of more or less constant width, in which are located small, finger-shaped vesicles. In view of these and other close structural relationships with the myofibrils it seems appropriate to assign to the system a role in the conduction of the excitatory impulse.

scholarly journals THE LOCALIZATION OF CHOLINESTERASE ACTIVITY IN RAT CARDIAC MUSCLE BY ELECTRON MICROSCOPY

1964 ◽  
Vol 23 (2) ◽  
pp. 217-232 ◽  
Author(s):  
Morris J. Karnovsky
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Sarcoplasmic Reticulum ◽  
Enzymatic Activity ◽  
Cardiac Muscle ◽  
Heart Muscle ◽  
Cholinesterase Activity ◽  
Physiological Role ◽  
Ultrastructural Level ◽  
Formalin Fixed

A method has been developed for localizing sites of cholinesterase activity in rat cardiac muscle by electron microscopy. The method utilizes thiocholine esters as substrates, and is believed to be dependent on the reduction of ferricyanide to ferrocyanide by thiocholine released by enzymatic activity. The ferrocyanide thus formed is captured by copper to form fine, electron-opaque deposits of copper ferrocyanide, which sharply delineate sites of enzymatic activity at the ultrastructural level. Cholinesterase activity in formalin-fixed heart muscle was localized: (a) in longitudinal elements of the sarcoplasmic reticulum, but not in the T, or transverse, elements; and (b) in the A band, with virtually no activity noted in the M band, or in the H zone. The I band was also negative. No activity was detected in the sarcolemma, or in invaginations of the sarcolemma at the level of the Z band. The perinuclear element of the sarcoplasmic (endoplasmic) reticulum was frequently strongly positive. Activity at all sites was completely abolished by omitting the substrates, or by inhibition with eserine 10-4 M and diisopropylfluorophosphate 10-5 M. Eserine 10-5 M completely inhibited reaction in the sarcoplasmic reticulum, and virtually abolished that in the A band. These observations, together with the use of the relatively specific substrates and suitable controls to eliminate non-enzymatic staining, indicate that cholinesterase activity was being demonstrated. The activity in rat heart against different substrates was that of non-specific cholinesterases, in accordance with biochemical data. The activity in the A band was considered to be probably due to myosincholinesterase. It is proposed that the localization of cholinesterases in myocardium at the ultrastructural level should be taken into account in considering the possible functions of these myocardial enzymes, and it is hoped that knowledge of their localization will open up new avenues of approach in considering their physiological role in myocardium, which at present is not definitely known.

scholarly journals Localization of phospholamban in smooth muscle using immunogold electron microscopy.

1988 ◽  
Vol 107 (2) ◽  
pp. 555-562 ◽  
Author(s):  
D G Ferguson ◽  
E F Young ◽  
L Raeymaekers ◽  
E G Kranias
Keyword(s):  
Electron Microscopy ◽  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Polyclonal Antibody ◽  
Muscle Cells ◽  
Immunogold Electron Microscopy ◽  
Cardiac Sarcoplasmic Reticulum

Phospholamban, the putative regulator of the Ca2+-ATPase in cardiac sarcoplasmic reticulum, was immunolocalized in canine visceral and vascular smooth muscle. Gently disrupted tissues were labeled with an affinity-purified phospholamban polyclonal antibody and indirect immunogold, using preembedding techniques. The sarcoplasmic reticulum of smooth muscle cells was specifically labeled with patches of immunogold distributed in a nonuniform fashion, while the sarcolemma did not appear to contain any phospholamban. The outer nuclear envelopes were also observed to be heavily labeled with the affinity-purified phospholamban polyclonal antibody. These findings suggest that phospholamban may play a role in the regulation of cytoplasmic and intranuclear calcium levels in smooth muscle cells.

Calcium release from cardiac sarcoplasmic reticulum induced by photorelease of calcium or Ins(1,4,5)P3

1990 ◽  
Vol 258 (2) ◽  
pp. H610-H615 ◽  
Author(s):  
J. C. Kentish ◽  
R. J. Barsotti ◽  
T. J. Lea ◽  
I. P. Mulligan ◽  
J. R. Patel ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Calcium Release ◽  
Force Response ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Excitation Contraction Coupling ◽  
Caged Compounds ◽  
Contraction Coupling ◽  
Inositol 1,4,5 Trisphosphate ◽  
Ventricular Trabeculae

The ability of Ca2+ or inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] to release Ca2+ from cardiac sarcoplasmic reticulum (SR) was investigated using saponin-skinned ventricular trabeculae from rats. To overcome diffusion delays, rapid increases in the concentrations of Ca2+ and Ins(1,4,5)P3 were produced by laser photolysis of “caged Ca2+” (Nitr-5) and “caged Ins(1,4,5)P3”. Photolysis of Nitr-5 to produce a small jump in [Ca2+] from pCa 6.8 to 6.4 induced a large and rapid force response (t1/2 = 0.89 s at 12 degrees C); the source of the Ca2+ that activated the myofibrils was judged to be the SR, since it was blocked by 0.1 mM ryanodine or 5 mM caffeine. A smaller, slower, and less consistent release of SR Ca2+ was produced by photorelease of Ins(1,4,5)P3. The results demonstrate that these caged compounds can be used to study excitation-contraction coupling in skinned multicellular preparations of cardiac muscle. The data are consistent with a major role for Ca2(+)-induced Ca2+ release in cardiac activation, whereas the role for Ins(1,4,5)P3 may be to modulate, rather than directly stimulate, SR Ca2+ release.

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