The aim of this study was to evaluate cell diversity by considering
how Ca2+ signaling has been adapted in skeletal muscle cell
function. We characterized single C2C12 myoblasts through
intracellular Ca2+ signaling kinetics after exposure to specific
drugs and calcium blockers using fast fluorescence
microspectrofluorimetry followed by ATP effect analysis, which
confirmed the expression of functional purinergic adenosine and
P2 receptors. Further, we found that glutamate sensitivity of
C2C12 cells was mediated by ionotropic glutamate receptors; on
the other hand, most cells were responsive to cyclopiazonic acid,
which inhibits the sarco-endoplasmic reticulum Ca2+-ATPase
pump. These results suggest that C2C12 cells possess functional
L- and P/Q-type voltage-operated Ca2+ channels, ryanodine
receptors and functional sarcoplasmic reticulum Ca2+ stores
(typical for muscle cells), adenosine and P2 purinergic receptors,
as well as ionotropic glutamate receptors. The evaluation of
intracellular Ca2+ signaling is a promising approach towards
a better understanding and control of the physiopathological
properties of myogenic cells that could be used as a predictive
factor in the selection of optimal cells for scaffold recellularization
or for tissue engineered constructs used in stem cell therapy.
Tissue differentiation and proliferation throughout fetal development interconnect with changes in the oxidative phosphorylation system (OXPHOS) on the cellular level. Reevaluation of the expression data revealed a significant increase in COX4 and MTATP6 liver transcription levels after the 22nd gestational week (GW) which inspired us to characterize its functional impact. Specific activities of cytochrome c oxidase (COX), citrate synthase (CS), succinate-coenzyme Q reductase (SQR) and mtDNA determined by spectrophotometry and RT-PCR were studied in a set of 25 liver and 18 skeletal muscle samples at 13th to 29th GW. Additionally, liver hematopoiesis (LH) was surveyed by light microscopy. The mtDNA content positively correlated with the gestational age only in the liver. The activities of COX, CS and SQR in both liver and muscle isolated mitochondria significantly decreased after the 22nd GW in comparison with earlier GW. A continuous decline of LH, not correlating with the documented OXPHOS-specific activities, was observed from the 14th to the 24th GW indicating their exclusive reflection of liver tissue processes. Two apparently contradictory processes of increasing mtDNA transcription and decreasing OXPHOS-specific activities seem to be indispensable for rapid postnatal adaptation to high energy demands. The inadequate capacity of mitochondrial energy production may be an important factor in the mortality of children born before the critical developmental point of the 22nd GW., H. Kolarová, J. Křížová, M. Hůlková, H. Hansiková, H. Hůlková, V. Smid, J. Zeman, T. Honzík, M. Tesarová., and Seznam literatury
Experimental hypothermia caused extensive changes in the number of both classes of insulin receptors in different rat tissues. In the liver, the number of high affinity insulin receptors (HAIRs) decreased by 50 % (from 25.3 to 12.6 fmol/mg membrane protein), whereas number of low affinity insulin receptors (LAIRs) was almost unchanged in comparison to normothermic animals (5.63 and 4.39 pmol/mg, respectively). In the adipose tissue, number of both classes was reduced - HAIRs by 81 % (from 24.0 to 4.50 fmol/mg) and LAIRs by 92 % (from 16.0 to 1.29 pmol/mg). In the skeletal muscle, capacity of HAIRs was not changed (16.2 and 19.3 fmol/mg in normo- and hypothermic animals, respectively), whereas number of LAIRs increased by 150 % (from 6.65 to 16.6 pmol/mg). Hypothermic rats also showed lower amount (by 85 %) of LAIRs in the heart muscle (9.37 and 1.43 pmol/mg in control and experimental animals, respectively). Simultaneously, no significant changes were found in HAIRs (16.3 and 11.9 fmol/mg, respectively) and LAIRs (4.43 and 3.88 pmol/mg, respectively) in the brain. These differences in insulin receptors responses to hypothermia may reflect different physiological role of insulin in the regulation of target cell metabolism and/or the differences in tissue distribution of the insulin receptor isoforms., T. Torlinska, M. Perz, E. Madry, T. Hryniewiecki, K. W. Nowak, P. Mackowiak., and Obsahuje bibliografii
This study was designed to determine whether the supplement of superoxide dismutase (SOD) could attenuate strain-induced oxidative damage to skeletal muscle in rats. Experimental animals were injured in right gastrocnemius muscles by a strain injury model. SOD-treated groups were given Cu/Zn SOD 10 000 U/kg body weight per day since injured, while control groups were given normal saline. Parameters of antioxidant and muscle damage were detected in plasma 3 and 7 days postinjury. The injured muscles were removed and fixed for histology observation and immunohisto-chemistry assay of desmin. The results showed that plasma levels of SOD, glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC) in SOD group were significantly higher than in the saline group on day 3 or 7, while the plasma creatine kinase (CK) and malondialdehyde (MDA) were lower in the SOD group than in the saline group. The histological examination of muscle sections revealed a lower degree of damage in the SOD group in which the expression level of desmin was higher than in the saline group. It is suggested that SOD supplement may attenuate strain-induced muscle damage and facilitate its regeneration
The metabolic turnover in the isolated in vitro perfused and superfused rat skeletal muscle (musculus gracilis cranialis) was enhanced by increasing the medium flow rate under relaxed conditions. In a recent study we have measured the tissue concentrations of second messengers: cyclic adenosine 3 ́5 ́- monophosphate (cAMP), cyclic guanosine 3 ́5 ́-
monophosphate (cGMP), and D-myo-inositol 1, 4, 5-trisphosphate (IP3) under similar experimental conditions to analyze their potential role in the described stimulation of metabolic rate by changes of perfusion flow rate. The tissue levels of the two second messengers’ cAMP and cGMP were not significantly changed after increasing the perfusion
flow rate and they probably have no transduction role in the induced alteration of skeletal muscle metabolism. However, the IP3 content was extremely reduced after increasing flow rate. This decrease in the tissue concentration of IP3 induced by increasing the flow rate indicates the possible role of IP3 in this signal transduction, leading to changes in
the cellular metabolic pathways.
Insulin resistance (IR) is the result of long-lasting positive energy balance and the imbalance between the uptake of energy rich substrates (glucose, lipids) and energy output. The defects in the metabolism of glucose in IR and type 2 diabetes are closely associated with the disturbances in the metabolism of lipids. In this review, we have summarized the evidence indicating that one of the important mechanisms underlying the development of IR is the impaired ability of skeletal muscle to oxidize fatty acids as a consequence of elevated glucose oxidation in the situation of hyperglycemia and hyperinsulinemia and the impaired ability to switch easily between glucose and fat oxidation in response to homeostatic signals. The decreased fat oxidation results into the accumulation of intermediates of fatty acid metabolism that are supposed to interfere with the insulin signaling cascade and in consequence negatively influence the glucose utilization. Pathologically elevated fatty acid concentration in serum is now accepted as an important risk factor leading to IR. Adipose tissue plays a crucial role in the regulation of fatty acid homeostasis. The adipose tissue may be the primary site where the early metabolic disturbances leading to the development of IR take place and the development of IR in other tissues follows. In this review we present recent evidence of mutual interaction between
skeletal muscle and adipose tissue in the establishment of IR and type 2 diabetes.