SABIIA - Sistema Aberto e Integrado de Informação em Agricultura (Sabiia)

Control of dual isoforms of Ca2+ release channels in muscle

Human skinned muscle fibers were used to investigate the effects of bovine serum albumin (BSA) on the tension/pCa relationship and on the functional properties of the Ca2+-release channel of the sarcoplasmic reticulum (SR). In both fast- and slow-type fibers, identified by their tension response to pSr 5.0, BSA (0.7-15 µM) had no effect on the Ca2+ affinity of the contractile proteins and elicited no tension per se in Ca2+-loaded fibers. In contrast, BSA (>1.0 µM) potentiated the caffeine-induced tension in Ca2+-loaded fibers, this effect being more intense in slow-type fibers. Thus, BSA reduced the threshold caffeine concentration required for eliciting detectable tension, and increased the amplitude, the rate of rise and the area under the curve...

Palavras-chave: Calcium-release channel; Sarcoplasmic reticulum; Human muscle fiber; Bovine serum albumin; Caffeine.

Ano: 1997

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X1997000500017

Differences in Ca2+-management between the ventricle of two species of neotropical teleosts: the jeju, Hoplerythrinus unitaeniatus (Spix & Agassiz, 1829), and the acara, Geophagus brasiliensis (Quoy & Gaimard, 1824)

RÍOS,EDUARDO; ZHOU,JINGSONG.

Here we compare excitation-contraction coupling in single muscle cells of frogs and rats. Because amphibians have isoform 3 (or b) of the ryanodine receptor/Ca2+ release channel, in addition to 1 (a), which is also present in the mammal, any extra feature present in the frog may in principle be attributed to isoform 3. Ca2+ release under voltage clamp depolarization has a peak and a steady phase in both taxonomic classes, but the peak is more marked in the frog, where the ratio of amplitudes of the two phases is voltage-dependent. This dependence is a hallmark of CICR. Confocal imaging identified Ca2+ sparks in the frog, but not in the voltage-clamped rat cells. Because Ca2+ sparks involve CICR both observations indicate that the contribution of CICR is...

Tipo: Journal article

Palavras-chave: Excitation-contraction coupling; Sarcoplasmic reticulum; Ca2+ sparks; Ryanodine receptor; Calcium-induced calcium release.

Ano: 2004

URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000400012

Neotropical Ichthyology

Costa,Monica Jones; Rantin,Francisco Tadeu; Kalinin,Ana Lúcia.

This study analyzed the physiological role of the cardiac sarcoplasmic reticulum (SR) of two neotropical teleosts, the jeju, Hoplerythrinus unitaeniatus (Erythrinidae), and the acara, Geophagus brasiliensis (Cichlidae). While the in vivo heart frequency (fH - bpm) of acara (79.6 ± 6.6) was higher than that of the jeju (50.3 ± 2.7), the opposite was observed for the ventricular inotropism (Fc - mN/mm²) at 12 bpm (acara = 28.66 ± 1.86 vs. jeju = 36.09 ± 1.67). A 5 min diastolic pause resulted in a strong potentiation of Fc (≅ 90%) of strips from jeju, which was completely abolished by ryanodine. Ryanodine also resulted in a ≅ 20% decrease in the Fc developed by strips from jeju at both subphysiological (12 bpm) and physiological (in vivo) frequencies....

Effect of exercise training on Ca2+ release units of left ventricular myocytes of spontaneously hypertensive rats

Palavras-chave: Excitation-contraction coupling; Ryanodine; Sarcoplasmic reticulum; Ventricle strips.

Ano: 2009

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1679-62252009000300015

Carneiro-Júnior,M.A.; Quintão-Júnior,J.F.; Drummond,L.R.; Lavorato,V.N.; Drummond,F.R.; Amadeu,M.A.; Oliveira,E.M.; Felix,L.B.; Cruz,J.S.; Mill,J.G.; Natali,A.J.; Prímola-Gomes,T.N..

In cardiomyocytes, calcium (Ca2+) release units comprise clusters of intracellular Ca2+ release channels located on the sarcoplasmic reticulum, and hypertension is well established as a cause of defects in calcium release unit function. Our objective was to determine whether endurance exercise training could attenuate the deleterious effects of hypertension on calcium release unit components and Ca2+ sparks in left ventricular myocytes of spontaneously hypertensive rats. Male Wistar and spontaneously hypertensive rats (4 months of age) were divided into 4 groups: normotensive (NC) and hypertensive control (HC), and normotensive (NT) and hypertensive trained (HT) animals (7 rats per group). NC and HC rats were submitted to a low-intensity treadmill running...

Effect of ryanodine on sinus node recovery time determined in vitro

Palavras-chave: Physical activity; Hypertension; Cardiomyocyte; Calcium handling; Sarcoplasmic reticulum.

Ano: 2014

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2014001100960

Energy interconversion by the sarcoplasmic reticulum Ca2+-ATPase: ATP hydrolysis, Ca2+ transport, ATP synthesis and heat production

Bassani,J.W.M.; Godoy,C.M.G.; Bassani,R.A..

Evidence has indicated that the sarcoplasmic reticulum (SR) might be involved in the generation of spontaneous electrical activity in atrial pacemaker cells. We report the effect of disabling the SR with ryanodine (0.1 µM) on the sinus node recovery time (SNRT) measured in isolated right atria from 4-6-month-old male Wistar rats. Electrogram and isometric force were recorded at 36.5oC. Two methods for sinus node resetting were used: a) pulse: a single stimulus pulse interpolated at coupling intervals of 50, 65 or 80% of the regular spontaneous cycle length (RCL), and b) train: a 2-min train of pulses at intervals of 50, 65 or 80% of RCL. Corrected SNRT (cSNRT) was calculated as the difference between SNRT (first spontaneous cycle length after stimulation...

Tipo: Info:eu-repo/semantics/other

Palavras-chave: Sinus node recovery time; Overdrive suppression; Electrical stimulation; Calcium; Sarcoplasmic reticulum; Ryanodine.

Ano: 1999

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X1999000800015

Anais da ABC (AABC)

MEIS,LEOPOLDO DE.

The sarcoplasmic reticulum of skeletal muscle retains a membrane bound Ca2+-ATPase which is able to interconvert different forms of energy. A part of the chemical energy released during ATP hydrolysis is converted into heat and in the bibliography it is assumed that the amount of heat produced during the hydrolysis of an ATP molecule is always the same, as if the energy released during ATP cleavage were divided in two non-interchangeable parts: one would be converted into heat, and the other used for Ca2+ transport. Data obtained in our laboratory during the past three years indicate that the amount of heat released during the hydrolysis of ATP may vary between 7 and 32 Kcal/mol depending on whether or not a transmembrane Ca2+ gradient is formed across the...

Fast kinetics of calcium dissociation from calsequestrin

Palavras-chave: Ca2+-ATPase; Ca2+ transport; Energy interconversion; ATP hydrolysis; Heat production; Sarcoplasmic reticulum.

Ano: 2000

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652000000300010

BELTRÁN,MARIANELA; BARRIENTOS,GENARO; HIDALGO,CECILIA.

We measured the kinetics of calcium dissociation from calsequestrin in solution or forming part of isolated junctional sarcoplasmic reticulum membranes by mixing calsequestrin equilibrated with calcium with calcium-free solutions in a stopped-flow system. In parallel, we measured the kinetics of the intrinsic fluorescence changes that take place following calcium dissociation from calsequestrin. We found that at 25ºC calcium dissociation was 10-fold faster for calsequestrin attached to junctional membranes (k = 109 s-1) than in solution. These results imply that calcium dissociation from calsequestrin in vivo is not rate limiting during excitation-contraction coupling. In addition, we found that the intrinsic fluorescence decrease for calsequestrin in...

Tipo: Journal article

Palavras-chave: Calcium-binding proteins; Ryanodine receptors; Sarcoplasmic reticulum; Calcium release kinetics; Excitation-contraction coupling; Skeletal and cardiac muscle.

Ano: 2006

URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602006000300011

Functional implications of RyR-DHPR relationships in skeletal and cardiac muscles

FRANZINI-ARMSTRONG,CLARA.

Dihydropyridine receptors (DHPRs) and ryanodine receptors (RyRs) interact during EC coupling within calcium release units, CRUs. The location of the two channels and their positioning are related to their role in EC coupling. als DHPR and RyR1 of skeletal muscle form interlocked arrays. Groups of four DHPRs (forming a tetrad) are located on alternate RyR1s. This association provides the structural framework for reciprocal signaling between the two channels. RyR3 are present in some skeletal muscles in association with RyR1 and in ratios up to 1:1. RyR3 neither induce formation of tetrads by DHPRs nor sustain EC coupling. RyR3 are located in a parajunctional position, in proximity of the RyR1-DHPR complexes, and they may be indirectly activated by calcium...

Tipo: Journal article

Palavras-chave: Calcium release units; Dihydropyridine receptors; Ryanodine receptors; Transverse tubules; Sarcoplasmic reticulum.

Ano: 2004

URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000400003

Redox regulation of calcium release in skeletal and cardiac muscle

Regulation of cardiac excitation-contraction coupling by sorcin, a novel modulator of ryanodine receptors

HIDALGO,CECILIA; ARACENA,PAULA; SANCHEZ,GINA; DONOSO,PAULINA.

In skeletal and cardiac muscle cells, specific isoforms of the Ryanodine receptor channels mediate Ca2+ release from the sarcoplasmic reticulum. These channels are highly susceptible to redox modifications, which regulate channel activity. In this work, we studied the effects of Ca2+ (endogenous agonist) and Mg2+ (endogenous inhibitor) on the kinetics of Ca2+ release from sarcoplasmic reticulum vesicles isolated from skeletal or cardiac mammalian muscle. Native skeletal vesicles exhibited maximal stimulation of release kinetics by 10-20 µM [Ca2+], whereas in native cardiac vesicles, maximal stimulation of release required only 1 µM [Ca2+]. In 10 µM [Ca2+], free [Mg2+] < 0.1 mM produced marked inhibition of release from skeletal vesicles but free [Mg2+]...

Tipo: Journal article

Palavras-chave: Redox state; Ryanodine receptors; Sarcoplasmic reticulum; Calcium release kinetics; Mg2+ inhibition; S-nitrosoglutathione.

Ano: 2002

URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602002000200009

SH Oxidation Stimulates Calcium Release Channels (Ryanodine Receptors) From Excitable Cells

FARRELL,EMILY F; ANTARAMIAN,ANAID; BENKUSKY,NANCY; ZHU,XINSHENG; RUEDA,ANGÉLICA; GÓMEZ,ANA M; VALDIVIA,HÉCTOR H.

Activation of Ca2+ release channels/ryanodine receptors (RyR) by the inward Ca2+ current (I Ca) gives rise to Ca2+-induced Ca2+ release (CICR), the amplifying Ca2+ signaling mechanism that triggers contraction of the heart. CICR, in theory, is a high-gain, self-regenerating process, but an unidentified mechanism stabilizes it in vivo. Sorcin, a 21.6 kDa Ca2+-binding protein, binds to cardiac RyRs with high affinity and completely inhibits channel activity. Sorcin significantly inhibits both the spontaneous activity of RyRs in quiescent cells (visualized as Ca2+ sparks) and the I Ca-triggered activity of RyRs that gives rise to [Ca2+]i transients. Since sorcin decreases the amplitude of the [Ca2+]i transient without affecting the amplitude of I Ca, the...

Tipo: Journal article

Palavras-chave: Sorcin; Ryanodine receptors; CICR; Dihydropyridine receptor; Sarcoplasmic reticulum.

Ano: 2004

URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000400015

STIM1/Orai1-mediated store-operated Ca2+ entry: the tip of the iceberg

HIDALGO,CECILIA; BULL,RICARDO; MARENGO,JUAN J; PÉREZ,CLAUDIO F; DONOSO,PAULINA.

The effects of redox reagents on the activity of the intracellular calcium release channels (ryanodine receptors) of skeletal and cardiac muscle, or brain cortex neurons, was examined. In lipid bilayer experiments, oxidizing agents (2,2'-dithiodipyridine or thimerosal) modified the calcium dependence of all single channels studied. After controlled oxidation channels became active at sub µM calcium concentrations and were not inhibited by increasing the calcium concentration to 0.5 mM. Subsequent reduction reversed these effects. Channels purified from amphibian skeletal muscle exhibited the same behavior, indicating that the SH groups responsible for modifying the calcium dependence belong to the channel protein. Parallel experiments that...

Tipo: Journal article

Palavras-chave: Calcium dependence; Neurons; Redox state; Ryanodine receptors; Sarcoplasmic reticulum; Skeletal and cardiac muscle.

Ano: 2000

URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602000000200011

Giachini,F.R.; Lima,V.V.; Hannan,J.L.; Carneiro,F.S.; Webb,R.C.; Tostes,R.C..

Highly efficient mechanisms regulate intracellular calcium (Ca2+) levels. The recent discovery of new components linking intracellular Ca2+ stores to plasma membrane Ca2+ entry channels has brought new insight into the understanding of Ca2+ homeostasis. Stromal interaction molecule 1 (STIM1) was identified as a Ca2+ sensor essential for Ca2+ store depletion-triggered Ca2+ influx. Orai1 was recognized as being an essential component for the Ca2+ release-activated Ca2+ (CRAC) channel. Together, these proteins participate in store-operated Ca2+ channel function. Defective regulation of intracellular Ca2+ is a hallmark of several diseases. In this review, we focus on Ca2+ regulation by the STIM1/Orai1 pathway and review evidence that implicates STIM1/Orai1 in...

The interaction of ryanoids with individual ryanodine receptor channels

Palavras-chave: Ca2+ release-activated Ca2+ channel; Sarcoplasmic reticulum; Intracellular Ca2+ store; Ca2+ influx.

Ano: 2011

URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2011001100002