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EN
The fraction of free fatty acids (FFA) is present in skeletal muscles. However, there is almost no data regarding regulation in the content of this intramuscular lipid pool. We took advantage of the isolated muscle preparation to examine whether: a) increasing exogenous concentration of FFA (500µM or 700µM, 30min) b) insulin (10.00 I.U./L, 30min), c) adrenalin (4.4 nM, 30min), or d) contractions (200ms, tetani, 1Hz, 30min), affect the FFA content inside myocytes. Incubation of soleus (S) and extensor digitorum longus (EDL) with increasing concentrations of exogenous FFA (from 500µM to 700µM) resulted in an increase in the total FFA fraction in both muscles studied (by 280.2% and 259.1%, respectively). In contracting muscles FFA pool was significantly reduced both in S (by 73.1%) and in EDL (by 31.1%). Neither stimulation by adrenalin nor insulin affected the total content of FFA fraction in the muscles examined. We conclude that a) increased availability of exogenous FFA at the sarcolemma level results in an increase in the size of intramuscular FFA fraction b) the intracellular FFA fraction is utilized by contracting muscles with regard to the fiber composition and to a greater extent in more oxidative muscles, c) FFA fraction remains stable upon stimulation by insulin or adrenalin.
EN
Data presented in this paper show that the size of the endogenous coenzyme Q (CoQ) pool is not a limiting factor in the activation of mitochondrial glyceropho- sphate-dependent respiration by exogenous CoQ3, since successive additions of succinate and NADH to brown adipose tissue mitochondria further increase the rate of oxygen uptake. Because the inhibition of glycerophosphate-dependent respiration by oleate was eliminated by added CoQ3, our data indicate that the activating effect of CoQ3 is related to the release of the inhibitory effect of endogenous free fatty acids (FFA). Both the inhibitory effect of FFA and the activating effect of CoQ3 could be demonstrated only for glycerophosphate-dependent respiration, while succinate- or NADH-dependent respiration was not affected. The presented data suggest differ­ences between mitochondrial glycerophosphate dehydrogenase and succinate or NADH dehydrogenases in the transfer of reducing equivalents to the CoQ pool.
EN
Krawczuk I. and Górski J.: The significance of plasma triacylglycerols in metabolism of free fatty acids and triacylgrylcerols in rat skeletal muscles. Acta Physiol. Pol., The continuous uptake of plasma triacyl- gylcerols has been shown to be necessary to maintain the stable resting concentration of free fatty acids and triacylglycerols only in a muscle composed of fast - twitch oxidative gylcolytic fibres.
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nr 03
147-154
EN
Free fatty acids (FFAs) are not only an important source of energy but they also play key roles in regulating various physiological responses. FFAs including short-chain fatty acids (SCFAs) have recently been demonstrated to act as ligands of several G-protein-coupled receptors (GPCRs) (FFA1, FFA2, FFA3, GPR84 and GPR120). FFA1 and GPR120 are activated by medium- and long chain fatty acids. GPR84 is activated by mediam-chain, but not long chain FFAs. On the other hand, FFA2 and FFA3 are both activated by SCFAs. Tissue distribution studies have indicated that FFA2 and FFA3 function as chemical sensors in the colon. For the involvement of SCFAs in the regulation of colonic motility, propionate and butyrate concentration- -dependently induced phasic and tonic contractions in rat colonic circular muscle. The responses were not observed in mucosal free preparation. Thus, FFA2 and FFA3 are important molecular devices to monitor the chemical composition in colonic lumen. For the local function of SCFAs, it should be stressed that individual SCFA has different mode of actions on colonic smooth muscles. These different effects may be due to the relative contribution of FFA2 and FFA3 on the control of intestinal muscle activity. In this article, we have reviewed the expression and functions of these molecules, especially FFA2 and FFA3 on the regulation of colonic motility.
EN
Mitochondria of the amoeba Acanthamoeba castellanii possess a free fatty acid-ac­tivated uncoupling protein (AcUCP) that mediates proton re-uptake driven by the mi­tochondrial proton electrochemical gradient. We show that AcUCP activity diverts energy from ATP synthesis during state 3 mitochondrial respiration in a fatty acid-dependent way. The efficiency of AcUCP in mitochondrial uncoupling increases when the state 3 respiratory rate decreases as the AcUCP contribution is constant at a given linoleic acid concentration while the ATP synthase contribution decreases with respiratory rate. Respiration sustained by this energy-dissipating process remains constant at a given linoleic acid concentration until more than 60% inhibition of state 3 respiration by n-butyl malonate is achieved. The present study supports the validity of the ADP/O method to determine the actual contributions of AcUCP (activated with various linoleic acid concentrations) and ATP synthase in state 3 respiration of A. castellanii mitochondria fully depleted of free fatty acid-activated and describes how the two contributions vary when the rate of succinate dehydrogenase is decreased by succinate uptake limitation.
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