Homogeneity of [3H]ouabain-binding sites in rat soleus muscle.
Ontology highlight
ABSTRACT:
SUBMITTER: Kjeldsen K
PROVIDER: S-EPMC1148728 | biostudies-other | 1988 Jan
REPOSITORIES: biostudies-other
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Project description:Sustained sarcolemma depolarization due to loss of the Na,K-ATPase function is characteristic for skeletal muscle motor dysfunction. Ouabain, a specific ligand of the Na,K-ATPase, has a circulating endogenous analogue. We hypothesized that the Na,K-ATPase targeted by the elevated level of circulating ouabain modulates skeletal muscle electrogenesis and prevents its disuse-induced disturbances. Isolated soleus muscles from rats intraperitoneally injected with ouabain alone or subsequently exposed to muscle disuse by 6-h hindlimb suspension (HS) were studied. Conventional electrophysiology, Western blotting, and confocal microscopy with cytochemistry were used. Acutely applied 10 nM ouabain hyperpolarized the membrane. However, a single injection of ouabain (1 µg/kg) prior HS was unable to prevent the HS-induced membrane depolarization. Chronic administration of ouabain for four days did not change the α1 and α2 Na,K-ATPase protein content, however it partially prevented the HS-induced loss of the Na,K-ATPase electrogenic activity and sarcolemma depolarization. These changes were associated with increased phosphorylation levels of AMP-activated protein kinase (AMPK), its substrate acetyl-CoA carboxylase and p70 protein, accompanied with increased mRNA expression of interleikin-6 (IL-6) and IL-6 receptor. Considering the role of AMPK in regulation of the Na,K-ATPase, we suggest an IL-6/AMPK contribution to prevent the effects of chronic ouabain under skeletal muscle disuse.
| S-EPMC8069997 | biostudies-literature
Project description:In the standard [3H]ouabain-binding assay for quantification of the Na,K-ATPase (Na+ + K+-dependent ATPase) concentration in rat skeletal muscles, samples are incubated for 2 X 60 min in 1 microM-[3H]ouabain at 37 degrees C followed by a wash-out for 4 X 30 min at 0 degree C. To obtain accurate determinations, values determined by this standard assay should be corrected for non-specific uptake and retention of [3H]ouabain (11% overestimation), loss of specifically bound [3H]ouabain during wash-out (21% underestimation), evaporation from muscle samples during weighing (4% overestimation), impurity of [3H]ouabain (5% underestimation) and incomplete saturation of [3H]ouabain binding sites (6% underestimation). Thus corrected the standard [3H]ouabain-binding assay determines the total Na,K-ATPase concentration. Hence, in the soleus muscle of 12-week-old rats the total [3H]ouabain-binding-site concentration is 278 +/- 20 pmol/g wet wt. This is at variance with the evaluation of the Na,K-ATPase concentration from Na,K-ATPase activity measurements in muscle membrane fractions, where the recovery of Na,K-ATPase is only 2-18%. Quantification of the total Na,K-ATPase concentration is of particular importance since it is a prerequisite for the discussion of quantitative aspects of the Na,K-ATPase.
| S-EPMC1147479 | biostudies-other
Project description:The plant alkaloid ryanodine, known to interact selectively with the intracellular Ca(2+)-release channel in skeletal and cardiac muscles, has been repeatedly reported to affect smooth-muscle contractile functions that are consistent with its intracellular action at the Ca(2+)-release channel sites. Direct evidence for the binding of [3H]ryanodine to smooth-muscle membranes is sparse. Following our recent detailed characterization of functional effects of ryanodine and a preliminary report on the presence of [3H]ryanodine binding sites in rat vas deferens smooth muscle, we now report in this study a detailed characterization of binding of [3H]ryanodine to smooth muscle at the subcellular-membrane level. The ryanodine receptor in rat vas deferens muscle layer is primarily of smooth-muscle origin and is localized at the subcellular membrane site that is consistent with its role as a Ca(2+)-release channel in the sarcoplasmic reticulum (SR). Ryanodine binding to its receptor is Ca(2+)-dependent, with half-maximal binding occurring within the physiologically relevant cytosolic Ca2+ concentration. It is also sensitive to many factors, including change in Mg2+ concentration, ionic strength and osmolarity across the membrane vesicles. Agents known to inhibit (Ruthenium Red, Mg2+) or enhance (caffeine, Na+, K+) the Ca(2+)-induced Ca2+ release also inhibit or enhance the binding of ryanodine. Quantitative differences in ryanodine receptors exist among smooth muscles and do not seem to parallel their SR contents. Results from the present study indicate both the need and the basis for future investigations of the functional role of the ryanodine receptor in different smooth muscles.
| S-EPMC1132409 | biostudies-other
Project description:Nitric oxide (NO), produced by NO-synthases via L-arginine oxidation, is an essential trigger for signaling processes involved in structural and metabolic changes in muscle fibers. Recently, it was shown that L-arginine administration prevented the decrease in levels of the muscle cytoskeletal proteins, desmin and dystrophin, in rat soleus muscle after 14 days of hindlimb unloading. Therefore, in this study, we investigated the effect of L-arginine administration on the degree of atrophy changes in the rat soleus muscles under unloading conditions, and on the content, gene expression, and phosphorylation level of titin, the giant protein of striated muscles, able to form a third type of myofilaments-elastic filaments. A 7-day gravitational unloading [hindlimb suspension (HS) group] resulted in a decrease in the soleus weight:body weight ratio (by 31.8%, p < 0.05), indicating muscle atrophy development. The content of intact titin (T1) decreased (by 22.4%, p < 0.05) and the content of proteolytic fragments of titin (T2) increased (by 66.7%, p < 0.05) in the soleus muscle of HS rats, compared to control rats. The titin gene expression and phosphorylation level of titin between these two groups were not significantly different. L-Arginine administration under 7-day gravitational unloading decreased the degree of atrophy changes and also prevented the decrease in levels of T1 in the soleus muscle as compared to HS group. Furthermore, L-arginine administration under unloading resulted in increased titin mRNA level (by 76%, p < 0.05) and decreased phosphorylation level of T2 (by 28%, p < 0.05), compared to those in the HS group. These results suggest that administration of L-arginine, the NO precursor, under unloading decreased the degree of atrophy changes, increased gene expression of titin and prevented the decrease in levels of T1 in the rat soleus muscle. The results can be used to search for approaches to reduce the development of negative changes caused by gravitational unloading in the muscle.
| S-EPMC6764413 | biostudies-literature
Project description:The effects of obesity on different musculoskeletal tissues are not well understood. The glycolytic quadriceps muscles are compromised with obesity, but due to its high oxidative capacity, the soleus muscle may be protected against obesity-induced muscle damage. To determine the time-course relationship between a high-fat/high-sucrose (HFS) metabolic challenge and soleus muscle integrity, defined as intramuscular fat invasion, fibrosis and molecular alterations over six time points. Male Sprague-Dawley rats were fed a HFS diet (n = 64) and killed at serial short-term (3 days, 1 week, 2 weeks, 4 weeks) and long-term (12 weeks, 28 weeks) time points. Chow-fed controls (n = 21) were killed at 4, 12, and 28 weeks. At sacrifice, animals were weighed, body composition was calculated (DXA), and soleus muscles were harvested and flash-frozen. Cytokine and adipokine mRNA levels for soleus muscles were assessed, using RT-qPCR Histological assessment of muscle fibrosis and intramuscular fat was conducted, CD68+ cell number was determined using immunohistochemistry, and fiber typing was assessed using myosin heavy chain protein analysis. HFS animals demonstrated significant increases in body fat by 1 week, and this increase in body fat was sustained through 28 weeks on the HFS diet. Short-term time-point soleus muscles demonstrated up-regulated mRNA levels for inflammation, atrophy, and oxidative stress molecules. However, intramuscular fat, fibrosis, and CD68+ cell number were similar to their respective control group at all time points evaluated. Therefore, the oxidative capacity of the soleus may be protective against diet-induced alterations to muscle integrity. Increasing oxidative capacity of muscles using aerobic exercise may be a beneficial strategy for mitigating obesity-induced muscle damage, and its consequences.
| S-EPMC5449557 | biostudies-literature
Project description:Tenotomy is the release of muscle preload that causes abrupt shortening of the muscle and models atrophy and fibrosis without inflammatory response. Fibrosis in the skeletal muscle is known to be triggered by TGF-β, which is activated by mediators of inflammatory events. As these were lacking, tenotomy provided an opportunity to investigate transcriptional events on a background without inflammation. An unbiased look at the transcriptome of tenotomy-immobilized soleus muscle revealed that the majority of the transcriptional changes took place in the first four weeks. The transcriptome provided clear-cut evidence for the upregulation of collagens and several extracellular matrix components that defined fibrotic remodeling of the skeletal muscle architecture as well as activation of the fibro-adipogenic precursors.
2016-05-23 | GSE73510 | GEO
Project description:It was observed that gravitational unloading during space missions and simulated microgravity in ground-based studies leads to both transformation of slow-twitch muscle fibers into fast-twitch fibers and to the elimination of support afferentation, leading to the "switching-off" of postural muscle motor units electrical activity. In recent years, plantar mechanical stimulation (PMS) has been found to maintain the neuromuscular activity of the hindlimb muscles. Nitric oxide (NO) was shown to be one of the mediators of muscle fiber activity, which can also promote slow-type myosin expression. We hypothesized that applying PMS during rat hindlimb unloading would lead to NO production upregulation and prevention of the unloading-induced slow-to-fast fiber-type shift in rat soleus muscles. To test this hypothesis, Wistar rats were hindlimb suspended and subjected to daily PMS, and one group of PMS-subjected animals was also treated with nitric oxide synthase inhibitor (L-NAME). We discovered that PMS led to sustained NO level in soleus muscles of the suspended animals, and NOS inhibitor administration blocked this effect, as well as the positive effects of PMS on myosin I and IIa mRNA transcription and slow-to-fast fiber-type ratio during rat hindlimb unloading. The results of the study indicate that NOS activity is necessary for the PMS-mediated prevention of slow-to-fast fiber-type shift and myosin I and IIa mRNA transcription decreases during rat hindlimb unloading.
| S-EPMC7866401 | biostudies-literature
Project description:This SuperSeries is composed of the SubSeries listed below.
2006-03-17 | GSE4492 | GEO
Project description:As demonstrated previously, digitonin-permeabilized Xenopus oocytes have a large internal pool of sodium pumps which are inaccessible to cytosolic ouabain [Schmalzing, Kröner & Passow (1989) Biochem. J. 260, 395-399]. Access to internal ouabain-binding sites required permeabilization of inner membranes with SDS. In the present study, micromolar free Ca2+ was found to stimulate ouabain binding in the digitonin-permeabilized cells (K0.5 0.5 microM-Ca2+, h 1.9, average of seven experiments) without disrupting intracellular membranes. Sustained incubation at 9 microM-Ca2+ was as effective as SDS in inducing access to the ouabain-binding sites of the internal sodium pumps. Omission of either Mg2+ or ATP completely abolished the Ca2+ effect. Half-maximal stimulation by Ca2+ required approx. 0.4 mM-MgATP. Of a variety of nucleotides tested, none was as effective as ATP (rank order ATP greater than ADP greater than ATP[S] (adenosine 5'-[gamma-thio]triphosphate) greater than CTP greater than UTP greater than ITP = XTP greater than GTP). Pi, AMP, cyclic AMP, cyclic GMP, GTP[S] (guanosine 5'-[gamma-thio]triphosphate) and a stable ATP analogue p[NH]ppA (adenosine 5'-[beta gamma-imido]triphosphate), were ineffective. The metalloendoproteinase inhibitor carbobenzoxy-Gly-Phe-amide reduced the Ca2+ effect by some 50%. Inhibitors of chymotrypsin and the Ca2+ proteinase calpain had no effect. Ca2+ ionophores (A23187 and ionomycin) and the polycations neomycin and polymixin B blocked the Ca2+ response entirely. Neomycin also abolished a Ca2(+)-independent stimulation of ouabain binding by the wasp venom mastoparan. The requirements for increasing the accessibility of ouabain-binding sites are remarkably similar to those for exocytosis in secretory cells, suggesting that oocytes and eggs possess a Ca2(+)-regulated pathway for the plasma membrane insertion of sodium pumps.
| S-EPMC1131652 | biostudies-other
Project description:Desformylflustrabromine (dFBr) is a positive allosteric modulator (PAM) of α4β2 and α2β2 nAChRs that, at concentrations >1 µM, also inhibits these receptors and α7 nAChRs. However, its interactions with muscle-type nAChRs have not been characterized, and the locations of its binding site(s) in any nAChR are not known. We report here that dFBr inhibits human muscle (αβεδ) and Torpedo (αβγδ) nAChR expressed in Xenopus oocytes with IC50 values of ∼ 1 μM. dFBr also inhibited the equilibrium binding of ion channel blockers to Torpedo nAChRs with higher affinity in the nAChR desensitized state ([(3)H]phencyclidine; IC50 = 4 μM) than in the resting state ([(3)H]tetracaine; IC50 = 60 μM), whereas it bound with only very low affinity to the ACh binding sites ([(3)H]ACh, IC50 = 1 mM). Upon irradiation at 312 nm, [(3)H]dFBr photoincorporated into amino acids within the Torpedo nAChR ion channel with the efficiency of photoincorporation enhanced in the presence of agonist and the agonist-enhanced photolabeling inhibitable by phencyclidine. In the presence of agonist, [(3)H]dFBr also photolabeled amino acids in the nAChR extracellular domain within binding pockets identified previously for the nonselective nAChR PAMs galantamine and physostigmine at the canonical α-γ interface containing the transmitter binding sites and at the noncanonical δ-β subunit interface. These results establish that dFBr inhibits muscle-type nAChR by binding in the ion channel and that [(3)H]dFBr is a photoaffinity probe with broad amino acid side chain reactivity.
| S-EPMC4468644 | biostudies-literature