The Role Of Intracellular Acidosis In Muscle Fatigue
The Role of Intracellular Acidosis in Muscle Fatigue Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 384) Muscle fatigue is often accompanied by an intracellular acidosis of variable size. The variability reflects the involvement of different metabolic pathways, the presence or absence of blood flow and the effectiveness of pH-regulating pathways. Intracellular acidosis affects many aspects of muscle cell function; for instance it reduces maximal Ca2+-activated force and Ca2+ sensitivity, slows the maximal shortening velocity and prolongs relaxation. However, acidosis is not the only metabolic change in fatigue which causes each of the above, and there are important aspects of muscle fatigue (e.g., the failure of Ca2+ release) which do not appear to be caused by acidosis. Muscle FatigueMouse Skeletal MuscleMyosin Light Chain PhosphorylationSingle Muscle FibreTetanic Contraction These 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. This is a preview of subscription content, log in to check access. Unable to display preview. Download preview PDF. Adams GR, Fisher MJ & Meyer RA (1991). Hypercapnic acidosis and increased H2PO4 concentration do not decrease force in cat skeletal muscle. American Journal of Physiology 260, C805C812. PubMed Google Scholar Allen DG, Lee JA & Westerblad H (1989). Intracellular calcium and force in isolated single muscle fibres from Xenopus. Journal of Physiology (London) 415, 433458. Google Scholar Amorena CE, Wilding TJ, Manchester JK & Roos A (1990). Changes in intracellular pH caused by high K+ in normal and acidified frog muscle. Journal of General Physiology 96, 959972. PubMed CrossRef Google Scholar B Continue reading >>
Sodium Bicarbonate Use
metabolic acidosis leads to adverse cardiovascular effects bicarbonate must be administered in a solution as sodium bicarbonate 8.4% solution contains 1mmol of HCO3-/mL and is very hypertonic (2,000mOsm/kg) goal of NaHCO3 administration in severe metabolic acidosis to counteract the negative cardiovascular effects of acidaemia alternatives to NaHCO3 include carbicarb, dichloroacetate, Tris/THAM Treatment of sodium channel blocker overdose (e.g. tricyclic overdose) Urinary alkalinisation (salicylate poisoning) Metabolic acidosis (NAGMA) due to HCO3 loss (RTA, fistula losses) Cardiac arrest (in prolonged resuscitation + documented severe metabolic acidosis) Diabetic ketoacidosis (very rarely, perhaps if shocked and pH < 6.8) Severe pulmonary hypertension with RVF to optimize RV function Severe ischemic heart disease where lactic acidosis is thought to be an arrhythmogenic risk hypernatraemia (1mmol of Na+ for every 1mmol of HCO3-) hyperosmolality (cause arterial vasodilation and hypotension) impaired oxygen unloading due to left shift of the oxyhaemoglobin dissociation curve removal of acidotic inhibition of glycolysis by increased activity of PFK hypercapnia (CO2 readily passes intracellularly and worsens intracellular acidosis) severe tissue necrosis if extravasation takes place bicarbonate increases lactate production by: increasing the activity of the rate limiting enzyme phosphofructokinase and removal of acidotic inhibition of glycolysis shifts Hb-O2 dissociation curve, increased oxygen affinity of haemoglobin and thereby decreases oxygen delivery to tissues POINTS TO REMEMBER WHEN USING BICARBONATE it is generally better to correct underlying cause of acidosis and give supportive care than to give sodium bicarbonate ensure adequate ventilation to eliminate CO2 pro Continue reading >>
Effects Of Intracellular Acidosis On Endothelial Function: An Overview.
1. J Crit Care. 2012 Apr;27(2):108-18. doi: 10.1016/j.jcrc.2011.06.001. Epub 2011Jul 27. Effects of intracellular acidosis on endothelial function: an overview. Crimi E(1), Taccone FS, Infante T, Scolletta S, Crudele V, Napoli C. (1)Department of Anesthesia and Critical Care Medicine, Shands Hospital, University of Florida, Gainesville, FL 32608, USA. The endothelium represents the largest functional organ in the human body playingan active role in vasoregulation, coagulation, inflammation, and microvascularpermeability. Endothelium contributes to maintain vascular integrity,intravascular volume, and tissue oxygenation promoting inflammatory networkresponse for local defense and repair. Acid-basis homeostasis is an importantphysiologic parameter that controls cell function, and changes in pH caninfluence vascular tone by regulating endothelium and vascular smooth musclecells. This review presents a current perspective of the effects of intracellularacidosis on the function and the basic regulatory mechanisms of endothelialcells.Copyright 2012. Published by Elsevier Inc. Continue reading >>
Intracellular Acidosis: Can It Delay The Inevitable?
Citation:Moseley, Richard H. (1990)."Intracellular acidosis: Can it delay the inevitable?." Hepatology 11(4): 707-708.
Role Of Extracellular And Intracellular Acidosis For Hypercapnia-induced Inhibition Of Tension Of Isolated Rat Cerebral Arteries.
Role of extracellular and intracellular acidosis for hypercapnia-induced inhibition of tension of isolated rat cerebral arteries. Department of Pharmacology, University of Aarhus, Denmark. The importance of smooth muscle cell pHi and pHo for the hypercapnic vasodilation of rat cerebral arteries was evaluated in vitro. Vessel segments were mounted in a myograph for isometric tension recording; pHi was measured by loading the smooth muscle cells with the fluorescent dye BCECF, and pHo was measured with a glass electrode. In all studies, Ca(2+)-dependent basal tension (in the absence of any agonist) and tension in the presence of arginine vasopressin were investigated. Control solution was physiological saline bubbled with 5% CO2 and containing 25 mmol/L HCO3- (pH 7.45 to 7.50). Induction of hypercapnic acidosis (10% CO2) or normocapnic acidosis (15 mmol/L HCO3-) caused significant inhibition of smooth muscle tension, and both conditions reduced pHi as well as pHo. N-Nitro-L-arginine significantly inhibited the relaxation to hypercapnic acidosis but had no significant effect on relaxation to normocapnic acidosis. Predominant extracellular acidosis, induced by reducing [HCO3-] from 25 to 9 mmol/L and CO2 from 5% to 2.5%, also caused inhibition of tension in steady state. By contrast, predominant intracellular acidosis, induced by increasing [HCO3-] from 25 to 65 mmol/L and CO2 from 5% to 15%, induced a small increase of basal tension and a small decrease of tension in the presence of arginine vasopressin. The responses to predominant intracellular or extracellular acidosis were qualitatively similar in the presence and absence of endothelium and in the presence and absence of N-nitro-L-arginine. It is concluded that the extracellular acidosis and not smooth muscle intracel Continue reading >>
Direct Activation Of Cloned Katp Channels By Intracellular Acidosis*
From the Department of Biology, Georgia State University, Atlanta, Georgia 30302-4010 ATP-sensitive K+(KATP) channels may be regulated by protons in addition to ATP, phospholipids, and other nucleotides. Such regulation allows a control of cellular excitability in conditions when pH is low but ATP concentration is normal. However, whether the KATP changes its activity with pH alterations remains uncertain. In this study we showed that the reconstituted KATP was strongly activated during hypercapnia and intracellular acidosis using whole-cell recordings. Further characterizations in excised patches indicated that channel activity increased with a moderate drop in intracellular pH and decreased with strong acidification. The channel activation was produced by a direct action of protons on the Kir6 subunit and relied on a histidine residue that is conserved in all KATP. The inhibition appeared to be a result of channel rundown and was not seen in whole-cell recordings. The biphasic response may explain the contradictory pH sensitivity observed in cell-endogenous KATP in excised patches. Site-specific mutations of two residues showed that pH and ATP sensitivities were independent of each other. Thus, these results demonstrate that the proton is a potent activator of the KATP. The pH-dependent activation may enable the KATP to control vascular tones, insulin secretion, and neuronal excitability in several pathophysiologic conditions. Continue reading >>
Bicarbonate Therapy And Intracellular Acidosis.
1. Clin Sci (Lond). 1997 Dec;93(6):593-8. Bicarbonate therapy and intracellular acidosis. (1)Renal Laboratory, St Thomas' Hospital, London, U.K. 1. The correction of metabolic acidosis with sodium bicarbonate remainscontroversial. Experiments in vitro have suggested possible deleterious effectsafter alkalinization of the extracellular fluid. Disequilibrium of carbon dioxideand bicarbonate across cell membranes after alkali administration, leading to thephenomenon of 'paradoxical' intracellular acidosis, has been held responsible forsome of these adverse effects. 2. Changes in intracellular pH in suspensions ofleucocytes from healthy volunteers were monitored using a fluorescentintracellular dye. The effect in vitro of increasing extracellular pH with sodiumbicarbonate was studied at different sodium bicarbonate concentrations. Lacticacid and propionic acid were added to the extracellular buffer to mimicconditions of metabolic acidosis. 3. The addition of a large bolus of sodiumbicarbonate caused intracellular acidification as has been observed previously.The extent of the intracellular acidosis was dependent on several factors, being most evident at higher starting intracellular pH. When sodium bicarbonate wasadded as a series of small boluses the reduction in intracellular pH was small.Under conditions of initial acidosis this was rapidly followed by intracellularalkalinization. 4. Although intracellular acidification occurs after addition of sodium bicarbonate to a suspension of human leucocytes in vitro, the effect isminimal when the conditions approximate those seen in clinical practice. Wesuggest that the observed small and transient lowering of intracellular pH isinsufficient grounds in itself to abandon the use of sodium bicarbonate in human acidosis. Continue reading >>
Metabolic acidosis is a condition that occurs when the body produces excessive quantities of acid or when the kidneys are not removing enough acid from the body. If unchecked, metabolic acidosis leads to acidemia, i.e., blood pH is low (less than 7.35) due to increased production of hydrogen ions by the body or the inability of the body to form bicarbonate (HCO3−) in the kidney. Its causes are diverse, and its consequences can be serious, including coma and death. Together with respiratory acidosis, it is one of the two general causes of acidemia. Terminology : Acidosis refers to a process that causes a low pH in blood and tissues. Acidemia refers specifically to a low pH in the blood. In most cases, acidosis occurs first for reasons explained below. Free hydrogen ions then diffuse into the blood, lowering the pH. Arterial blood gas analysis detects acidemia (pH lower than 7.35). When acidemia is present, acidosis is presumed. Signs and symptoms Symptoms are not specific, and diagnosis can be difficult unless the patient presents with clear indications for arterial blood gas sampling. Symptoms may include chest pain, palpitations, headache, altered mental status such as severe anxiety due to hypoxia, decreased visual acuity, nausea, vomiting, abdominal pain, altered appetite and weight gain, muscle weakness, bone pain, and joint pain. Those in metabolic acidosis may exhibit deep, rapid breathing called Kussmaul respirations which is classically associated with diabetic ketoacidosis. Rapid deep breaths increase the amount of carbon dioxide exhaled, thus lowering the serum carbon dioxide levels, resulting in some degree of compensation. Overcompensation via respiratory alkalosis to form an alkalemia does not occur. Extreme acidemia leads to neurological and cardia Continue reading >>
Bicarbonate Therapy And Intracellular Acidosis
1. The correction of metabolic acidosis with sodium bicarbonate remains controversial. Experiments in vitro have suggested possible deleterious effects after alkalinization of the extracellular fluid. Disequilibrium of carbon dioxide and bicarbonate across cell membranes after alkali administration, leading to the phenomenon of 'paradoxical' intracellular acidosis, has been held responsible for some of these adverse effects. 2. Changes in intracellular pH in suspensions of leucocytes from healthy volunteers were monitored using a fluorescent intracellular dye. The effect in vitro of increasing extracellular pH with sodium bicarbonate was studied at different sodium bicarbonate concentrations. Lactic acid and propionic acid were added to the extracellular buffer to mimic conditions of metabolic acidosis. 3. The addition of a large bolus of sodium bicarbonate caused intracellular acidification as has been observed previously. The extent of the intracellular acidosis was dependent on several factors, being most evident at higher starting intracellular pH. When sodium bicarbonate was added as a series of small boluses the reduction in intracellular pH was small. Under conditions of initial acidosis this was rapidly followed by intracellular alkalinization. 4. Although intracellular acidification occurs after addition of sodium bicarbonate to a suspension of human leucocytes in vitro, the effect is minimal when the conditions approximate those seen in clinical practice. We suggest that the observed small and transient lowering of intracellular pH is insufficient grounds in itself to abandon the use of sodium bicarbonate in human acidosis. Do you want to read the rest of this article? ... However, an experimental study by Benjamin et al. on dogs subjected to hemorrhagic shoc Continue reading >>
The Use Of Sodium Bicarbonate In The Treatment Of Acidosis In Sepsis: A Literature Update On A Long Term Debate
Volume2015(2015), Article ID605830, 7 pages The Use of Sodium Bicarbonate in the Treatment of Acidosis in Sepsis: A Literature Update on a Long Term Debate 1Internal Medicine Department, University Hospital of Patras, 26500 Rion, Greece 2University of Patras School of Medicine, 26500 Rion, Greece 3Intensive Care Department, Brugmann University Hospital, 1030 Brussels, Belgium 4Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA Received 22 March 2015; Revised 29 June 2015; Accepted 1 July 2015 Copyright 2015 Dimitrios Velissaris et al. This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Introduction. Sepsis and its consequences such as metabolic acidosis are resulting in increased mortality. Although correction of metabolic acidosis with sodium bicarbonate seems a reasonable approach, there is ongoing debate regarding the role of bicarbonates as a therapeutic option. Methods. We conducted a PubMed literature search in order to identify published literature related to the effects of sodium bicarbonate treatment on metabolic acidosis due to sepsis. The search included all articles published in English in the last 35 years. Results. There is ongoing debate regarding the use of bicarbonates for the treatment of acidosis in sepsis, but there is a trend towards not using bicarbonate in sepsis patients with arterial blood gas . Conclusions. Routine use of bicarbonate for treatment of severe acidemia and lactic acidosis due to sepsis is subject of controversy, and current opinion does not favor routine use of bicarbonates. However, available evidence is inconclusive, and Continue reading >>
Pyruvate In The Correction Of Intracellular Acidosis: A Metabolic Basis As A Novel Superior Buffer
Pyruvate in the Correction of Intracellular Acidosis: A Metabolic Basis as a Novel Superior Buffer Tel. +1 847 394 6250, Fax +1 847 394 4621, E-Mail [email protected] The review focuses on biochemical metabolisms of conventional buffers and emphasizes advantages of sodium pyruvate (Pyr) in the correction of intracellular acidosis. Exogenous lactate (Lac) as an alternative of natural buffer, bicarbonate, consumes intracellular protons on an equimolar basis, regenerating bicarbonate anions in plasma while the completion of gluconeogenesis and/or oxidation occurs via tricarboxylic-acid cycle in mitochondria mainly in liver and kidney, or heart. The general assumption that Lac is metabolized to bicarbonate in liver to serve as a buffer has been questioned. Pyr as a novel buffer would be superior to conventional ones in the correction of metabolic acidosis. Several likely biochemical mechanisms of Pyr action are discussed. Experimental evidence, in vivo, strongly suggested that Pyr would be particularly efficient in the correction of severe acidemia: type A lactic acidosis, hypercapnia with cardiac arrest, and diabetic and alcoholic ketoacidosis in animal experiments and clinic settings. Because of its multi-cytoprotection, Pyrs not only correct acidosis, but also benefit theunderlying dysfunction of vital organs. In addition, Pyr is also a potential buffer component of dialysis solutions. However, the instability of Pyr in aqueous solutions restricts its clinical applications as a therapeutic agent. Attempts to create a stable Pyr preparation are needed. Since 1970s, pyruvate (Pyr) has become increasingly attractive in the protection of dysfunctional vital organs, particularly in myocardial ischemia and reperfusion injury, pointing to a potential therapeutic value for the dy Continue reading >>
Hemodynamic Consequences Of Severe Lactic Acidosis In Shock States: From Bench To Bedside
Hemodynamic consequences of severe lactic acidosis in shock states: from bench to bedside Kimmoun et al.; licensee BioMed Central.2015 The Erratum to this article has been published in Critical Care 2017 21:40 Lactic acidosis is a very common biological issue for shock patients. Experimental data clearly demonstrate that metabolic acidosis, including lactic acidosis, participates in the reduction of cardiac contractility and in the vascular hyporesponsiveness to vasopressors through various mechanisms. However, the contributions of each mechanism responsible for these deleterious effects have not been fully determined and their respective consequences on organ failure are still poorly defined, particularly in humans. Despite some convincing experimental data, no clinical trial has established the level at which pH becomes deleterious for hemodynamics. Consequently, the essential treatment for lactic acidosis in shock patients is to correct the cause. It is unknown, however, whether symptomatic pH correction is beneficial in shock patients. The latest Surviving Sepsis Campaign guidelines recommend against the use of buffer therapy with pH 7.15 and issue no recommendation for pH levels <7.15. Furthermore, based on strong experimental and clinical evidence, sodium bicarbonate infusion alone is not recommended for restoring pH. Indeed, bicarbonate induces carbon dioxide generation and hypocalcemia, both cardiovascular depressant factors. This review addresses the principal hemodynamic consequences of shock-associated lactic acidosis. Despite the lack of formal evidence, this review also highlights the various adapted supportive therapy options that could be putatively added to causal treatment in attempting to reverse the hemodynamic consequences of shock-associated lactic Continue reading >>
8.7 Use Of Bicarbonate In Metabolic Acidosis
8.7 Use of Bicarbonate in Metabolic Acidosis Metabolic acidosis causes adverse metabolic effects (see Section 5.4 ). In particular the adverse effects on the cardiovascular system may cause serious clinical problems. Bicarbonate is an anion and cannot be given alone. Its therapeutic use is as a solution of sodium bicarbonate. An 8.4% solution is a molar solution (ie it contains 1mmol of HCO3- per ml) and is the concentration clinically available in Australia. This solution is very hypertonic (osmolality is 2,000 mOsm/kg). The main goal of alkali therapy is to counteract the extracellular acidaemia with the aim of reversing or avoiding the adverse clinical effects of the acidosis (esp the adverse cardiovascular effects). Other reasons for use of bicarbonate in some cases of acidosis are: to promote alkaline diuresis (eg to hasten salicylate excretion) 8.7.2 Undesirable effects of bicarbonate administration In general, the severity of these effects are related to the amount of bicarbonate used. These undesirable effects include: 8.7.3 Important points about bicarbonate 1. Ventilation must be adequate to eliminate the CO2 produced from bicarbonate Bicarbonate decreases H+ by reacting with it to to produce CO2 and water. For this reaction to continue the product (CO2) must be removed. So bicarbonate therapy can increase extracellular pH only if ventilation is adequate to remove the CO2. Indeed if hypercapnia occurs then as CO2 crosses cell membranes easily, intracellular pH may decrease even further with further deterioration of cellular function. 2. Bicarbonate may cause clinical deterioration if tissue hypoxia is present If tissue hypoxia is present, then the use of bicarbonate may be particularly disadvantageous due to increased lactate production (removal of acidotic i Continue reading >>
Species-specific Differences In Thermal Tolerance May Define Susceptibility To Intracellular Acidosis In Reef Corals.
Species-specific differences in thermal tolerance may define susceptibility to intracellular acidosis in reef corals. Gibbin, E. M.Putnam, H. M.Gates, R. D.Nitschke, M. R.Davy, S. K. It is widely acknowledged that temperature stress affects an organism's sensitivity to ocean acidification and vice versa, yet it is not clear how the two are mechanistically linked. Here, we induced thermal stress in two coral species with differing bleaching susceptibilities to measure how a reduction in photosynthetic performance impacts intracellular pH (pH(i)) regulation in the symbiotic dinoflagellates (Symbiodinium sp.) and their host coral cells. Our hypothesis was that thermally induced photosynthetic dysfunction in the symbiont would prevent the efficient removal of additional CO2, lowering its buffering capacity and thus increasing the host cell's susceptibility to intracellular acidosis. To test this, we exposed Pocillopora damicornis (a thermally sensitive coral) and Montipora capitata (a thermally resilient coral) to four different temperature treatments (23.8, 25.5, 28 and 31 A degrees C) for 1 week. We then isolated intact symbiotic coral endodermal cells, placed them in a live-cell chamber attached to a confocal microscope and bathed them in CO2-acidified seawater (similar to pH 7.6) for 30 min, before measuring the light-adapted pH(i) of both the host cell and its symbiont. Cells isolated from P. damicornis were more prone to cellular acidosis (declines in pH(i) of 11 and 8 % in host and symbiont, respectively, at 31 A degrees C relative to 23.8 A degrees C) than cells isolated from M. capitata (5 and 4 %, respectively). These results highlight the important role of Symbiodinium productivity (in addition to a range of physico-chemical factors such as skeletal morphology a Continue reading >>
Effect Of Sodium Bicarbonate On Intracellular Ph Under Different Buffering Conditions - Sciencedirect
Volume 49, Issue 5 , May 1996, Pages 1262-1267 Effect of sodium bicarbonate on intracellular pH under different buffering conditions Author links open overlay panel JacquesLevrautDr. Effect of sodium bicarbonate on intracellular pH under different buffering conditions. Previous in vitro studies have reported a paradoxical exacerbation of intracellular acidosis following bicarbonate therapy due to the generated CO2 entering the cytoplasm. However, these studies were conducted in nonphysiological Hepes-buffered media. We compared the effect of a sodium bicarbonate load on the intracellular pH (pHi) of hepatocytes placed in nonbicarbonate (NBBS) or bicarbonate (BBS) buffering systems. The pHi of isolated rat hepatocytes was measured using the fluorescent pH sensitive dye BCECF and a single-cell imaging technique. Cells were placed in medium buffered with or Hepes. All media were adjusted to pH 7 with L-lactic acid or HCl. An acute 45mM sodium bicarbonate load was added to each medium and the changes in pHi were measured every three seconds for 90 seconds. The sodium bicarbonate load caused rapid cytoplasmic acidification of cells in NBBS (N = 50, P < 0.001). In contrast, hepatocytes in BBS underwent a marked increase in pHi (N = 50, P < 0.001) without any initial decrease in pHi. These differences were highly significant for the buffer (P < 0.01), but not for the acid used. We conclude that sodium bicarbonate exacerbates intracellular acidosis only in a NBBS. Hence, in vitro studies reporting a paradoxical intracellular acidosis following bicarbonate therapy cannot be extrapolated to the in vivo buffering conditions, and should not be used to argue against bicarbonate therapy. Continue reading >>