• The Korean Journal of Physiology
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• v.29 no.1
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• pp.13-27
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• 1995

single $K^{+}$ channels of skeletal muscle from the rat and frog were into planar lipid bilayers and their properties were studied. Fusion was induced by an osmotic gradient. Of the four types of $K^{+}$ channels recorded, the two most frequently observed were a voltage and $Ca^{2+}-activated$ $K^{+}$ channel and a $K^{+}$ channel with a prominent conductance substate. The first $K^{+}$ channel was identified as the large $Ca^{2+}-activated$ $K^{+}$ (BK) channel because the open-state probability was increased with depolarization (e-fold change per $10.6{\pm}3.5$ mV, n=8) and internal $Ca^{2+}$ (half-activation at $16.7{\pm}3.8$ mV, n=8, pCa 4) and its conductance was large ($247{\pm}4.9$ pS, n=24 in 0.1 M KCI). Lifetime distributions of open- and closed-states could be fitted with single exponentials of several milliseconds. The mean open- and closed-lifetimes were linearly dependent on the intracellular $[Ca^{2+}]$ and $1/[Ca^{2+}]$, respectively. The second $K^{+}$ channel showed a conductance substate at $30{\sim}60%$ of the open state. Its current-voltage relation was linear in the range of $-80\;{\sim}\;+80\;mV$. The slope conductance of the substate and open-state were 40 and 144 pS in 0.2 M KCl, respectively. The channel was highly selective for $K^{+}$ over Cl. The open-state probability was weakly voltage-dependent (e-fold change per 35 mV. The lifetime distributions of open- and closed-states were fitted with two exponentials and the major gating occurred slowly at several hundred milliseconds. Based on the above results, we think the second type of $K^{+}$ channel is the sarcoplasmic reticulum $K^{+}$ (SRK) channel. In addition, both types of channel were also incorporated into the lipids extracted from the skeletal muscle. The channel properties recorded in the bilayers termed from synthetic and extracted lipids were qualitatively similar. Our data indicate that BK and SRK channels are rich in the skeletal muscle and their properties and regulation could be effectively studied in planar lipid bilayer.

• The Korean Journal of Pharmacology
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• v.31 no.2
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• pp.207-217
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• 1995

To investigate the functional and immunological properties of the Ca-release channel in the sarcoplasmic reticulum(SR) of the eel skeletal muscle, $[^3H]ryanodine$ binding, SDS gel electrophoresis, $^{45}Ca\;release$ studies, and immunoblot assay were carried out in the SR of the eel skeletal muscle. Maximal binding sites(Bmax) and $K_D$ values of $[^3H]ryanodine$ for Ca-release channel of the SR of the eel skeletal muscle were $19.44{\pm}1.40\;pmole/mg$ protein and $15.55{\pm}1.69\;nM$, respectively. $[^3H]Ryanodine$ binding to RyR was increased by calcium and AMP. The SR of the eel skeletal muscle has two high molecular weight bands on the SDS PAGE. The mobility of upper band was more slower than the single band of the rabbit skeletal muscle, and that of the lower band was similar with the single band of canine cardiac muscle. Vesicular $^{45}Ca-release$ was activated by calcium. Ca-induced $^{45}Ca-release$ was significantly inhibited by $MgCl_2(2\;mM)$, ruthenium red$(10\;{/mu}M)$ or tetracaine(1 mM), but not by high concentration of calcium itself. AMP-induced $^{45}Ca-release$ was slightly occurred only in the absence of calcium, it was not inhibited by $MgCl_2$ or ruthenium red. Caffeine also increased $^{45}Ca-release$ from the SR vesicles, but it was not affected by $MgCl_2$ or ruthenium red. Polyclonal Ab against rat skeletal muscle RyR is reacted with that of rabbit, but not reacted with that of the eel skeletal muscle. These results suggested that ryanodine receptor of the SR of the eel skeletal muscle is showing some similar properties with that of mammalian skeletal muscle, but might be an another isotype channel having two bands which is less sensitive to AMP, not cross-reacted with antisera against rat RyR, and not inhibited by high concentration of calcium.

• The Korean Journal of Zoology
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• v.17 no.2
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• pp.93-102
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• 1974

Fragmente dsarcoplasmic reticulum of rabbit skeletal muscle was prepared and biochemical properties of its ATPase activity were studied. The ATPase of the fragments could be distinguished as $Mg^++ - ATPase and (Mg^++ - Ca^++)$-ATPase. The activity of $(Mg^++ - Ca^++)$-ATPase was predominant over that of $Mg^++$-ATPase in the temperature range of $0 \\sim 40^\\circ C$ and in the pH 6.4$\\sim$7.6. At higher temperatures the predominance of $(Mg^++ - Ca^++)$-ATpase was far greater. The apparent energies of activation were 14 kcal/mole for $Mg^++$-ATPase, 21kcal/mole for $(Mg^++ - Ca^++)$-ATPase, and 18kcal/mole for total ATPase. Changes in pH and Mg concentration did not alter the energies of activation of these ATPases. The Km values of these ATPases were found to be 0.36 mM for $Mg^++$-ATPase, 2.20 mM for $(Mg^++ - Ca^++)$-ATpase, and 0.86 mM for total ATPase.

• Applied Microscopy
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• v.17 no.2
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• pp.31-40
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• 1987

The tentacular retractor muscle has many arrays of muscle fiber bundles under the epithelial layer. Most of muscle fiber bundles are arranged in parallel to the longitudinal axes of muscle fibers and a small number of them perpendiculary to them. These smooth muscle cells are filled with compactly arranged myosins and actins. These microfilaments, when the tentacle is protracted, keep abreast with straight for-ward-lined shapes while these microfilaments, when it is retracted, with curved shapes. The foldings in the sarcolemma of the muscle cell, when the tentacle is retracted, lead to the formation of normal subsurface tubules along with which a few mitochondria are included. It is thought that the formation of the sarcolemmal differentiation like the subsurface tubules has a close relation with the protraction and retraction of the tentacle. Mitochondria are found throughout the muscle cell, and sarcoplasmic reticulum (SR) developed greatly in the exoplasm close to the sarcolemma and associated with the cell membrane. Dense bodies are distributed irregularly and thin filaments are scattered around the thick filament in cross-sections, but the thin filaments may be arranged in complete or partial orbits around thick filaments. Complete orbits are infrequent.

• Genomics & Informatics
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• v.5 no.2
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• pp.77-82
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• 2007

Serotonin (5-HT), the endogenous nonselective 5-HT receptor agonist, activates the inositol-1,4,5-triphosphate/calcium $(InsP3/Ca^{2+})$ signaling pathway and exerts both stimulatory and inhibitory actions on cAMP production and neuromodulin secretion in rat hypothalamic neurons. Specific mRNA transcripts for 5-HT1A, 5-HT2C and 5-HT4 were identified in rat hypothalamic neurons. These experiments were supported by combined techniques such as cAMP and a $Ca^{2+}$ assays in order to elucidate the associated receptors and signaling pathways. The cAMP production and neuromodulin release were profoundly inhibited during the activation of the Gi-coupled 5-HT1A receptor. Treatment with a selective agonist to activate the Gq-coupled 5-HT2C receptor stimulated InsP3 production and caused $Ca^{2+}$ release from the sarcoplasmic reticulum. Selective activation of the Gs-coupled 5-HT4 receptor also stimulated cAMP production, and caused an increase in neuromodulin secretion. These findings demonstrate the ability of 5-HT receptor subtypes expressed in neurons to induce neuromodulin production. This leads to the activation of single or multiple G-proteins which regulate the $InsP3/Ca^{2+}/PLC-{\gamma}$ and adenyl cyclase / cAMP signaling pathways.

• YAKHAK HOEJI
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• v.35 no.1
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• pp.45-60
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• 1991

lonophores, uniquely, create specific pathways of ion permeability in model and cell membranes. Calcium-transporting ionophores of microbiological origin, such as A23187 and ionomycin, have been used as experimental tools to elucidate the physiological role of calcium as a second messenger in many cell types. These ionophores are believed to bypass the initial ligand-receptor step in the activation of cells by increasing membrane permeability to calcium. In this report, we shall discuss several naturally occurring substances that share some properties of calcium-ionophores, primarily concentrating on oxidized fatty acids. We have previously demonstrated that oxidized linoteic and arachidonic acids, obtained either by lipoxygenase catalysis or nonenzymatic processes, significantly promote calcium translocation in a two-phase partition model and modulate calcium-transporting function in the isolated sarcoplasmic reticulum vesicles obtained from mammalian hearts. We have also confirmed that calcium-ionophoric properties are due not to their general amphiphilic nature of certain lipids, but to distinct structural characteristics. Although there are some skeptical views on the occurrence of ionophores in higher organisms, increasing evidence suggests that membrane lipids or their derivatives may serve as physiological calcium-ionophores. Abnormal accumulation of lipid peroxidation products(particularly end products), however, may be associated with the general oxidative damages as seen in many pathological conditions.

• Biomedical Science Letters
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• v.8 no.1
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• pp.21-27
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• 2002

To investigate an effect of bum on the cardiac function, we studied some biochemical assay, ultrastructural changes and stereological analysis in heart tissue. Sprague-Dawley rats were induced a 15% total body surface area scald burn. 5 and 24 hours later, the heart was excised. Burned rats showed the decrease of heart weight per body weight (%) compared with control. The activity of serum aspartate aminotransferase was significantly increased at 5 (p＜0.001) and 24 hours (p＜0.01) after burn compared with control. And the activity of serum LDH was decreased at 5 hours after burn but increased at 24 hours compared with control. Ultrastructurally, enlargement of interstitium and destruction of sarcolemma were observed at 5 and 24 hours after burn. Especially at 5 hours postburn, hypercontraction band was noted and at 24 hours, wavy fiber and muscle fraying were noted. In stereological changes, volume density of mitochondria and myofibril was significantly decreased at postburn 5 and 24 hours. But volume density of sarcoplasmic reticulum was significantly increased at postburn 5 hours. Our data suggest that dermal scald bum causes myocardial dysfunction.

• BMB Reports
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• v.47 no.2
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• pp.69-79
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• 2014

$Ca^{2+}$ release from intracellular stores and influx from extracellular reservoir regulate a wide range of physiological functions including muscle contraction and rhythmic heartbeat. One of the most ubiquitous pathways involved in controlled $Ca^{2+}$ influx into cells is store-operated $Ca^{2+}$ entry (SOCE), which is activated by the reduction of $Ca^{2+}$ concentration in the lumen of endoplasmic or sarcoplasmic reticulum (ER/SR). Although SOCE is pronounced in non-excitable cells, accumulating evidences highlight its presence and important roles in skeletal muscle and heart. Recent discovery of STIM proteins as ER/SR $Ca^{2+}$ sensors and Orai proteins as $Ca^{2+}$ channel pore forming unit expedited the mechanistic understanding of this pathway. This review focuses on current advances of SOCE components, regulation and physiologic and pathophysiologic roles in muscles. The specific property and the dysfunction of this pathway in muscle diseases, and new directions for future research in this rapidly growing field are discussed.

• Archives of Plastic Surgery
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• v.33 no.1
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• pp.31-38
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• 2006

The effect of melatonin on morphological changes after ischemia-reperfusion injury was investigated in rat skeletal muscle. Dimethyl-sulfoxide(DMSO) was also tested for comparison. Muscle injury was evaluated in 4 groups as a single laparotomy group(control), ischemia-reperfusion group, DMSO group, melatonin group. Left hind limb ischemia was induced for 4 hours by vascular clamping of the common femoral artery and followed by 24 hours of reperfusion. The midportion of gastrocnemius muscle was taken for histological evaluation. In light microscopic study, ischemia-reperfusion group showed severe neutrophil infiltration, interstitial edema, and partial loss or degeneration of muscle fibers. The muscle tissue of melatonin group showed relatively normal architecture with mild inflammatory cell infiltration. In electron microscopic study, dilated cisternae of sarcoplasmic reticulum, dilated mitochondria with electron loose matrix and dilated cristae, disordered or loss of myofilament, indistinct A-band and I-band, intracytoplasmic vacuoles, and markedly decreased glycogen granules were observed in ischemia-reperfusion group. But relatively well maintained A-band, I-band, Z-line, M-line, and mildly dilated mitochondria with well preserved cristae were observed in melatonin group. The DMSO group showed intermediately attenuated ultrastructural changes. The results show that melatonin improves morphologically ischemia-reperfusion injury more effectively than DMSO. In conclusion, melatonin seems to be a promising agent that can salvage the skeletal muscle from severe ischemia-reperfusion injury.

• Molecules and Cells
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• v.26 no.3
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• pp.265-269
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• 2008

Calumenin, a multiple EF-hand $Ca^{2+}$ binding protein is located in the SR of mammalian heart, but the functional role of the protein in the heart is unknown. In the present study, an adenovirus gene transfer system was employed for neonatal rat heart to examine the effects of calumenin over-expression (Calu-OE) on $Ca^{2+}$ transients. Calu-OE (8 folds) did not alter the expression levels of DHPR, RyR2, NCX, SERCA2, CSQ and PLN. However, Calu-OE affected several parameters of $Ca^{2+}$ transients. Among them, prolongation of time to 50% baseline ($T_{50}$) was the most outstanding change in electrically-evoked $Ca^{2+}$ transients. The higher $T_{50}$ was due to an inhibition of SERCA2-mediated $Ca^{2+}$ uptake into SR, as tested by oxalate-supported $Ca^{2+}$ uptake. Furthermore, co-IP study showed a direct interaction between calumenin and SERCA2. Taken together, calumenin in the cardiac SR may play an important role in the regulation of $Ca^{2+}$ uptake during the EC coupling process.