Regulation Of Cytoplasmic Ca2 Research Articles

Effect of Shensong Yangxin on heart failure in preserved ejection fraction rat model

Purpose: To investigate the interventional effect of ShensongYangxin (SSYX) on heart failure (HF) using preserved ejection fraction (HFpEF) rat model.Methods: HFpEF rat model was established using abdominal aorta coarctation method and randomly divided into a positive drug control group; SSYX at high, medium, and low dosage groups; and normal control group. After 8 weeks oral treatment of SSYX, echocardiography and cardiac catheterization were used to investigate the effects of SSYX on HFpEF rat cardiac functions, including mean heart rate (HR), left ventricle anterior and posterior wall thicknesses at end diastole (LVAWd + LVPWd), left ventricular internal diameter at end diastole (LVIDd), and left ventricle mass (LVM).Results: SSYX markedly decreased heart weight and improved survival rate (p < 0.01) after 12 weeks of treatment. The expression of NT-proBNP decreased in a dose-dependent manner and was significantly lower in SSYX treatment groups (p < 0.01). Compared with normal control group, expression of CaMK II, PKA and RyR2 was significantly lower (p < 0.005), while expression level of SERCA2a significantly increased after 4 g/kg/day SSYX treatment (p < 0.01).Conclusion: SSYX significantly attenuates HFpEF-induced cardiac dysfunction and increases survival rate, suggesting that SSYX may prevent HF via regulation of cytoplasmic Ca2+ handling. SSYX reduces plasma NT-proBNP levels, lending support for its therapeutic potential in HF management.Keywords: Heart failure, Ejection fraction, ShensongYangxin

In vivo Ca2+ dynamics induced by Ca2+ injection in individual rat skeletal muscle fibers.

In contrast to cardiomyocytes, store overload‐induced calcium ion (Ca2+) release (SOICR) is not considered to constitute a primary Ca2+ releasing system from the sarcoplasmic reticulum (SR) in skeletal muscle myocytes. In the latter, voltage‐induced Ca2+ release (VICR) is regarded as the dominant mechanism facilitating contractions. Any role of the SOICR in the regulation of cytoplasmic Ca2+ concentration ([Ca2+]i) and its dynamics in skeletal muscle in vivo remains poorly understood. By means of in vivo single fiber Ca2+ microinjections combined with bioimaging techniques, we tested the hypothesis that the [Ca2+]i dynamics following Ca2+ injection would be amplified and fiber contraction facilitated by SOICR. The circulation‐intact spinotrapezius muscle of adult male Wistar rats (n = 34) was exteriorized and loaded with Fura‐2 AM to monitor [Ca2+]i dynamics. Groups of rats underwent the following treatments: (1) 0.02, 0.2, and 2.0 mmol/L Ca2+ injections, (2) 2.0 mmol/L Ca2+ with inhibition of ryanodine receptors (RyR) by dantrolene sodium (DAN), and (3) 2.0 mmol/L Ca2+ with inhibition of SR Ca2+ ATPase (SERCA) by cyclopiazonic acid (CPA). A quantity of 0.02 mmol/L Ca2+ injection yielded no detectable response, whereas peak evoked [Ca2+]i increased 9.9 ± 1.8% above baseline for 0.2 mmol/L and 23.8 ± 4.3% (P < 0.05) for 2.0 mmol/L Ca2+ injections. The peak [Ca2+]i in response to 2.0 mmol/L Ca2+ injection was largely abolished by DAN and CPA (−85.8%, −71.0%, respectively, both P < 0.05 vs. unblocked) supporting dependence of the [Ca2+]i dynamics on Ca2+ released by SOICR rather than injected Ca2+ itself. Thus, this investigation demonstrates the presence of a robust SR‐evoked SOICR operant in skeletal muscle in vivo.

Hypoxic pulmonary hypertension: the paradigm is changing.

Hypoxic pulmonary hypertension: the paradigm is changing.

Transient Receptor Potential (TRP) and Cch1-Yam8 Channels Play Key Roles in the Regulation of Cytoplasmic Ca2+ in Fission Yeast

The regulation of cytoplasmic Ca2+ is crucial for various cellular processes. Here, we examined the cytoplasmic Ca2+ levels in living fission yeast cells by a highly sensitive bioluminescence resonance energy transfer-based assay using GFP-aequorin fusion protein linked by 19 amino acid. We monitored the cytoplasmic Ca2+ level and its change caused by extracellular stimulants such as CaCl2 or NaCl plus FK506 (calcineurin inhibitor). We found that the extracellularly added Ca2+ caused a dose-dependent increase in the cytoplasmic Ca2+ level and resulted in a burst-like peak. The overexpression of two transient receptor potential (TRP) channel homologues, Trp1322 or Pkd2, markedly enhanced this response. Interestingly, the burst-like peak upon TRP overexpression was completely abolished by gene deletion of calcineurin and was dramatically decreased by gene deletion of Prz1, a downstream transcription factor activated by calcineurin. Furthermore, 1 hour treatment with FK506 failed to suppress the burst-like peak. These results suggest that the burst-like Ca2+ peak is dependent on the transcriptional activity of Prz1, but not on the direct TRP dephosphorylation. We also found that extracellularly added NaCl plus FK506 caused a synergistic cytosolic Ca2+ increase that is dependent on the inhibition of calcineurin activity, but not on the inhibition of Prz1. The synergistic Ca2+ increase is abolished by the addition of the Ca2+ chelator BAPTA into the media, and is also abolished by deletion of the gene encoding a subunit of the Cch1-Yam8 Ca2+ channel complex, indicating that the synergistic increase is caused by the Ca2+ influx from the extracellular medium via the Cch1-Yam8 complex. Furthermore, deletion of Pmk1 MAPK abolished the Ca2+ influx, and overexpression of the constitutively active Pek1 MAPKK enhanced the influx. These results suggest that Pmk1 MAPK and calcineurin positively and negatively regulate the Cch1-Yam8 complex, respectively, via modulating the balance between phosphorylation and dyphosphorylation state.

Calcium ATPase and respiratory muscle function

The sarcoplasmic reticulum (SR) of striated muscle is a highly specialized intracellular membrane system that plays a key role in the contraction-relaxation cycle of muscle. Its primary function is the regulation of cytoplasmic Ca2+ concentration. A key element in this regulation is the Sarco(endo)plasmic reticulum Ca2+-adenosine triphosphatase (SERCA), which by sequestering Ca2+ into the SR, induces and maintains relaxation. It has been extensively studied with respect to structure and mechanism of action, and more recently to gene expression. Three separate genes encode five SERCA isoforms, two of which, SERCA 1 and SERCA 2, are expressed in skeletal muscle. In the first part of this review we focus on the general properties of the Ca2+ pump (structure and function and regulation of activity). In the second part we describe variations in SERCA expression in various physiological and pathological situations. These have essentially been studied in the heart and skeletal muscles, with data in respiratory muscles being very limited.

Significance of Ca2+ and K+ in Micrasterias Growth and Morphogenesis

Significance of Ca 2+ and K+ for the complex morphogenesis of Micrasterias, which takes place through multipolar tip growth, was investigated. Studies with different external Ca2+ concentrations and Ca2+ channel inhibitors LaCl3 and verapamil indicate that Ca2+ and Ca2+ channels are essential in the development, while treatments with different K+ concentrations and K+ channel inhibitor TEA demonstrate that potassium or K+ channels are not needed in the process, albeit the existence of K + channels. K+ is not needed even for the regulation of turgor pressure, which was found to decrease clearly during cell development. The plasma membrane ATPase inhibitors diethylstilbesterol (DES) and Na-orthovanadate stop morphogenesis and indicate the importance of ion pumps in the developmental process. Both supraoptimal, external K+ and Ca2+ cause abundant Ca2+ precipitate formation in chloroplasts, which shows that chloroplasts are important in regulation of cytoplasmic Ca2+ metabolism and that K+ activates the uptake of Ca 2+ through Ca2+ channels.

Handling of Cytoplasmic Ca2+ by the Sarcoplasmic Reticulum during α1-Adrenoceptor-Mediated Contraction of Rat Mesenteric Resistance Arteries

We investigated the role of the sarcoplasmic reticulum (SR) in the regulation of cytoplasmic Ca2+ ([Ca2+]i) during alpha 1-adrenoceptor-mediated contraction in rat mesenteric resistance arteries. Phenylephrine (PE) at 1 microM elevated the tension and [Ca2+]i measured with fura-2 in Ca(2+)-containing PSS, but did not do so in Ca(2+)-free PSS, suggesting that the contraction elicited by this concentration depends on the Ca2+ influx. Caffeine (100 mM) was shown to discharge Ca2+ in the SR, and cyclopiazonic acid (CPA, 10 microM) was shown to inhibit the Ca2+ uptake into the SR in these arteries. In resting arteries, both CPA and ryanodine (10 microM) sustainedly elevated [Ca2+]i without affecting the tension. In PE-stimulated arteries, both agents caused transient increase in [Ca2+]i, which was larger than that in resting arteries, and augmented the contraction. In the presence of PE, the caffeine-evoked [Ca2+]i transient was more greatly decreased after the application of ryanodine than after CPA. The CPA-induced rise in [Ca2+]i could be ascribed to inhibition of Ca2+ buffering by the SR, and the ryanodine-induced one can be attributed to the acceleration of Ca2+ release. It is suggested that both Ca2+ release from and Ca2+ uptake into the SR are enhanced during PE-induced contraction, which depends on the transmembrane Ca2+ influx.

Steroid hormone actions at the plasma membrane: Induced calcium uptake and exocytotic events

Calcium as an intracellular second messenger is not a new concept, although the subject is undergoing a resurgence in interest, in part reflecting our current appreciation of calcium channels and their role in Ca2+ influx, as well as the regulation of cytoplasmic Ca2+ movements by phosphoinositide metabolism (Michell, 1986). Perhaps the most intriguing aspect of the topic is that the agonists are not restricted to a single structural class, but include neurotransmitters, peptide hormones, and steroid hormones (see Table 1). Parallels in signal transduction between divergent structural classes of regulatory substances have been proposed before (Szego, 1978). The current work will attempt to focus more closely on systems where agonist-mediated changes in cellular calcium culminate in an exocytotic event.

Inositol trisphosphate, calcium and muscle contraction.

The identity of organelles storing intracellular calcium and the role of Ins(1,4,5)P3 in muscle have been explored with, respectively, electron probe X-ray microanalysis (EPMA) and laser photolysis of 'caged' compounds. The participation of G-protein(s) in the release of intracellular Ca2+ was determined in saponin-permeabilized smooth muscle. The sarcoplasmic reticulum (SR) is identified as the major source of activator Ca2+ in both smooth and striated muscle; similar (EPMA) studies suggest that the endoplasmic reticulum is the major Ca2+ storage site in non-muscle cells. In none of the cell types did mitochondria play a significant, physiological role in the regulation of cytoplasmic Ca2+. The latency of guinea pig portal vein smooth muscle contraction following photolytic release of phenylephrine, an alpha 1-agonist, is 1.5 +/- 0.26 s at 20 degrees C and 0.6 +/- 0.18 s at 30 degrees C; the latency of contraction after photolytic release of Ins(1,4,5)P3 from caged Ins(1,4,5)P3 is 0.5 +/- 0.12 s at 20 degrees C. The long latency of alpha 1-adrenergic Ca2+ release and its temperature dependence are consistent with a process mediated by G-protein-coupled activation of phosphatidylinositol 4,5 bisphosphate (PtdIns(4,5)P2) hydrolysis. GTP gamma S, a non-hydrolysable analogue of GTP, causes Ca2+ release and contraction in permeabilized smooth muscle. Ins(1,4,5)P3 has an additive effect during the late, but not the early, phase of GTP gamma S action, and GTP gamma S can cause Ca2+ release and contraction of permeabilized smooth muscles refractory to Ins(1,4,5)P3. These results suggest that activation of G protein(s) can release Ca2+ by, at least, two G-protein-regulated mechanisms: one mediated by Ins(1,4,5)P3 and the other Ins(1,4,5)P3-independent. The low Ins(1,4,5)P3 5-phosphatase activity and the slow time-course (seconds) of the contractile response to Ins(1,4,5)P3 released with laser flash photolysis from caged Ins(1,4,5)P3 in frog skeletal muscle suggest that Ins(1,4,5)P3 is unlikely to be the physiological messenger of excitation-contraction coupling of striated muscle. In contrast, in smooth muscle the high Ins(1,4,5)P3-5-phosphatase activity and the rate of force development after photolytic release of Ins(1,4,5)P3 are compatible with a physiological role of Ins(1,4,5)P3 as a messenger of pharmacomechanical coupling.

Kinetics of inositol 1,4,5-trisphosphate and inositol cyclic 1:2,4,5-trisphosphate metabolism in intact rat parotid acinar cells. Relationship to calcium signalling.

Stimulation of rat parotid acinar cells by the muscarinic cholinergic receptor agonist methacholine results in the formation of inositol 1,4,5-trisphosphate [1,4,5)IP3) and inositol cyclic 1:2,4,5-trisphosphate [c1:2,4,5)IP3) which, after 40 min, accumulate to a ratio of 1:0.57. The turnover rates of these inositol trisphosphates have been determined in cholinergically stimulated rat parotid cells by measuring the degradation of the 3H-labeled compounds following receptor blockade. (1,4,5)IP3 is rapidly metabolized, with a half-time of 7.6 s; (c1:2,4,5)IP3 declines much more slowly with a half-time of almost 10 min. Because the formation and metabolism of (c1:2,4,5)IP3 are so slow, (c1:2,4,5)IP3 gradually accumulates upon prolonged receptor activation. Inositol trisphosphate turnover was compared to the receptor-mediated changes in cytoplasmic Ca2+ concentration, as measured by the fluorescent Ca2+ indicator, fura-2. The Ca2+ signal decays upon termination of inositol phosphate formation and returns to base line within 30 s. Thus, while (c1:2,4,5)IP3 may have some yet unknown biological effects on Ca2+ homeostasis, its metabolism seems far too slow to be the primary regulator of cytosolic Ca2+ levels under long term stimulatory conditions. The rate at which the Ca2+ signal decays is, however, somewhat slowed after prolonged agonist stimulation. Furthermore, the capacity of the cells to mobilize intracellular Ca2+ in response to a second agonist stimulation is slightly delayed when the duration of the first stimulus is prolonged. The results suggest that the regulation of cytoplasmic Ca2+ levels may be more complicated than initially realized and could depend on the combined actions of more than one inositol polyphosphate.

The effects of continuous illumination on the function and structure of Micrasterias torreyi Bail. (Conjugatophyceae)

Abstract. The division rate of Micrasterias torreyi cells grown under continuous illumination first accelerated but soon slowed down, and the cells lost their ability to divide after about 1 month. During the treatment the cells became pale green, the pyrenoids became fewer in number and defects appeared in the chloroplasts. After 1 month, the cells also soon died, even when subjected to intermittent illumination. The most striking structural alterations were found in the chloroplasts: the starch granules lost their typical structure, the lamellae were damaged and numerous electron dense precipitates appeared in the chloroplasts. The precipitates were similar to those formed in cells treated with supraoptimal external calcium concentrations and X‐ray microanalysis showed that the precipitates were rich in calcium in both cases. The results suggest that light controls and activates the Ca2+ uptake in the plasma membrane as well as in the chloroplast envelope, that the large sized chloroplasts of Micrasterias are effective in regulation of cytoplasmic Ca2+ concentration, and that the injuries caused by continuous illumination may be largely due to the accumulation of Ca2+ in the chloroplasts.

The hepatic microsomal Ca2+ sequestering system.

The hepatic microsomal Ca2+ sequestering system is analogous to that of sarcoplasmic reticulum and fulfills a similar role to it; namely, regulation of cytoplasmic Ca2+ concentration. It does so by taking up Ca2+ in an ATP dependent manner and releases it by either the reversal of the uptake process and/or by a different, unknown mechanism.KeywordsATPase ActivitySarcoplasmic ReticulumMicrosomal FractionCoupling FactorMicrosomal ProteinThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Dysfunction of calcium handling by smooth muscle in hypertension.

Dysfunction of ion handling, including binding and fluxes (passive and active transport) of physiologically important ions such as potassium, sodium, calcium, and magnesium, by vascular smooth muscle cell membranes has repeatedly been reported to be associated with the pathophysiology of hypertension. The specific purpose of this review is to summarize and evaluate the evidence for alterations of calcium ion (Ca2+) handling by vascular smooth muscle in various forms of hypertension in the animal model on the basis that regulation of cytoplasmic Ca2+ concentration is a complex and yet vitally important process for a normal function of vascular smooth muscle and that derangement of such a regulation may result in excessive retention of cytoplasmic Ca2+, contribute toward increase of total peripheral resistance, and ultimately lead to elevation of blood pressure. Emphasis is placed upon the consideration of the usefulness of the subcellular membrane fractionation technique in studies of binding and transport of Ca2+ by vascular and nonvascular smooth muscle membranes from genetic as well as experimental hypertensive rats. The limitations of the interpretation of data using such an approach are also considered. Decreased active transport of Ca2+ across isolated plasma membrane vesicles from large and small arteries occurs in several but not all forms of hypertension. This membrane abnormality also occurs in nonvascular smooth muscles and other tissues or cells not confined to the cardiovascular system in genetic hypertension, but not in experimental hypertension. A hypothesis of general membrane defects in spontaneous hypertension is proposed.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructure, function and composition of smooth muscle.

Filamentous myosin is present in both relaxed (myosin light chains unphosphorylated) and contracted (light chains phosphorylated) vascular smooth muscle. The organization of myosin and actin filaments and the insertion of the latter on cytoplasmic and plasma membrane bound dense bodies is consistent with a mini sarcomere-like organization and a sliding filament mechanism of contraction in smooth muscle. Mitochondria are high capacity, low affinity Ca stores in smooth muscle. They do not play a role in the regulation of cytoplasmic Ca2+ at physiological levels. The localization and Ca content of the junctional sarcoplasmatic reticulum (SR) is consistent with this organelle being the major intracellular source of activator Ca released by excitatory transmitters. Repeated contractions in the absence of extracellular Ca2+ (thought to represent recycling of intracellular activator Ca2+) can be demonstrated if the excitatory agent is not allowed to remain in contact with the smooth muscle throughout relaxation.; the demonstration of "recycling" is facilitated if the efflux of cellular Ca2+ is blocked. The rise in total cytoplasmic calcium measured with electron probe analysis during a maintained (30 min) contracture in rabbit portal-anterior mesenteric vein smooth muscle (approximately 0.9 mol/kg dry cytoplasm) is greater than the amount of Ca that could be bound to calmodulin.