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Acidosis Effects

Physiological Effects Of Hyperchloraemia And Acidosis

Physiological Effects Of Hyperchloraemia And Acidosis

Physiological effects of hyperchloraemia and acidosis Chelsea and Westminster NHS Foundation Trust Chelsea and Westminster NHS Foundation Trust BJA: British Journal of Anaesthesia, Volume 101, Issue 2, 1 August 2008, Pages 141150, J. M. Handy, N. Soni; Physiological effects of hyperchloraemia and acidosis, BJA: British Journal of Anaesthesia, Volume 101, Issue 2, 1 August 2008, Pages 141150, The advent of balanced solutions for i.v. fluid resuscitation and replacement is imminent and will affect any specialty involved in fluid management. Part of the background to their introduction has focused on the non-physiological nature of normal saline solution and the developing science about the potential problems of hyperchloraemic acidosis. This review assesses the physiological significance of hyperchloraemic acidosis and of acidosis in general. It aims to differentiate the effects of the causes of acidosis from the physiological consequences of acidosis. It is intended to provide an assessment of the importance of hyperchloraemic acidosis and thereby the likely benefits of balanced solutions. Hyperchloraemic acidosis is increasingly recognized as a clinical entity, a new enemy within, that had gone otherwise unnoticed for decades. Although any associated morbidity may be subtle at present, there is a trend in current evidence to suggest that hyperchloraemic acidosis may have adverse consequences which may be circumvented by the use of balanced solutions. These consequences, both theoretical and clinical, may result from hyperchloraemia, acidosis, or both. There is some evidence of hyperchloraemia causing problems, but at present the clinical relevance is uncertain. The literature does appear to be unified in stating that acidosis results in adverse physiological effects bu Continue reading >>

Acidosis - An Overview | Sciencedirect Topics

Acidosis - An Overview | Sciencedirect Topics

Acidosis is an important prognostic factor in survival from respiratory failure during COPD exacerbation, and thus early correction of acidosis is an essential goal of therapy. Katherine Ahn Jin, in Comprehensive Pediatric Hospital Medicine , 2007 Acidosis is defined as an abnormal clinical process that causes a net gain in hydrogen ions (H+) in the extracellular fluid. Metabolic acidosis occurs when there is an accumulation of H+ or a loss of bicarbonate ions (HCO3) and is reflected by a decrease in plasma HCO3 (<22 mEq/L). Respiratory acidosis occurs when there is an accumulation of carbon dioxide (CO2) and is reflected by an increase in the arterial partial pressure of carbon dioxide (Pco2 >40 mm Hg). Clinically, acid-base scenarios can involve a primary acidosis or alkalosis with or without compensation, or a mixed acid-base disorder. The pH reflects the net effect of these processes (Fig. 27-1). The term acidemia is defined as an abnormal decrease in blood pH (<7.37). Sharma S. Prabhakar M.D., M.B.A., F.A.C.P., F.A.S.N., in Medical Secrets (Fifth Edition) , 2012 What is the conceptual difference between an AG and a non-AG metabolic acidosis? An AG acidosis is caused by the addition of a nonvolatile acid to the ECF. Examples include diabetic ketoacidosis, lactic acidosis, and uremic acidosis. A non-AG acidosis commonly (but not exclusively) represents a loss of . Examples include lower GI losses from diarrhea and urinary losses due to renal tubular acidosis (RTA). Therefore, when approaching a patient with an AG acidosis, one should look for the source and identity of the acid gained. By contrast, when evaluating a patient with a non-AG acidosis, one should begin by looking for the source of the Mario G. Bianchetti, Alberto Bettinelli, in Comprehensive Pediatric Ne Continue reading >>

Acute Effects Of Acidosis On Protein And Amino Acid Metabolism In Perfused Rat Liver

Acute Effects Of Acidosis On Protein And Amino Acid Metabolism In Perfused Rat Liver

Acute effects of acidosis on protein and amino acid metabolism in perfused rat liver 1Department of Physiology, Charles University Prague, Hradec Krlov, Czech Republic 2Department of Pharmacology, Charles University Prague, Hradec Krlov, Czech Republic 3University Hospital Motol, Prague, Czech Republic Correspondence: Dr Milan Holeek, Department of Physiology, Charles University Medical Faculty, imkova 870, 500 38 Hradec Krlov, Czech Republic. Tel.:/Fax: +420 49 5518190; E-mail: [email protected] Received 2003 Feb 5; Accepted 2003 Aug 1. Copyright 2003 Blackwell Publishing Ltd This article has been cited by other articles in PMC. Acidosis is frequently associated with protein wasting and derangements in amino acid metabolism. As its effect on protein metabolism is significantly modulated by other abnormal metabolic conditions caused by specific illnesses, it is difficult to separate out the effects on protein metabolism solely due to acidosis. The aim of the present study was to evaluate, using a model of isolated perfused rat liver, the direct response of hepatic tissue to acidosis. We have compared hepatic response to perfusion with a solution of pH 7.2 and 7.4 (controls). Parameters of protein and amino acid metabolism were measured using both recirculation and single-pass technique with 4,5-[3H]leucine, [114C]leucine and [114C]ketoisocaproate (ketoleucine) as tracers and on the basis of difference of amino acid levels in perfusion solution at the beginning and end of perfusion. In liver perfused with a solution of pH 7.2, we observed higher rates of proteolysis, protein synthesis, amino acid utilization and urea production. Furthermore, the liver perfused with a solution of pH 7.2 released a higher amount of proteins to perfusate than the liver perfused with a s Continue reading >>

The Effects Of Acidosis And Alkalosis On Long Bone Vascular Resistance.

The Effects Of Acidosis And Alkalosis On Long Bone Vascular Resistance.

The effects of acidosis and alkalosis on long bone vascular resistance. Mayo Graduate School of Medicine, Rochester, Minnesota. This study used an ex vivo perfusion model to investigate the direct effects of acidosis and alkalosis on the vascular resistance of the canine tibia. Baseline vascular resistance (BVR) and the vascular smooth muscle response to bolus doses of norepinephrine (NE) (0.025-3.2 nmol) and periarterial sympathetic nerve stimulation (NS) (10-25 Hz: 9 V, 2 ms pulses, 10 s) were studied. In Group I, these parameters were measured at normal pH (duration 7.34-7.44) and then during acidosis (pH 7.2-7.33). In Group II, they were measured at normal pH and then during alkalosis (pH 7.47-7.58). In Group III (control), they were measured serially at a normal pH. Alkalosis increased BVR by 56% (p < 0.0001). Acidosis attenuated (18% reduction) and alkalosis enhanced (66% increase) the vasoconstrictor action of NE (p < 0.0001). Acidosis also attenuated (11% reduction) the effect of sympathetic NS (p = 0.012). It is concluded that perfusion pH influences the sensitivity of long bone resistance vessels to circulating NE and sympathetic NS. Thus, local concentration of hydrogen ions may provide bone with a mechanism to autoregulate blood flow. Continue reading >>

5.4 Metabolic Acidosis - Metabolic Effects

5.4 Metabolic Acidosis - Metabolic Effects

5.4 Metabolic Acidosis - Metabolic Effects A metabolic acidosis can cause significant physiological effects, particularly affecting the respiratory and cardiovascular systems. Hyperventilation ( Kussmaul respirations ) - this is the compensatory response Shift of oxyhaemoglobin dissociation curve (ODC) to the right Decreased 2,3 DPG levels in red cells (shifting the ODC back to the left) Sympathetic overactivity (incl tachycardia, vasoconstriction,decreased arrhythmia threshold) Resistance to the effects of catecholamines Increased bone resorption (chronic acidosis only) Shift of K+ out of cells causing hyperkalaemia 5.4.2 Some Effects have Opposing Actions. The cardiac stimulatory effects of sympathetic activity and release of catecholamines usually counteract the direct myocardial depression while plasma pH remains above 7.2. At systemic pH values less than this, the direct depression of contractility usually predominates. The direct vasodilatation is offset by the indirect sympathetically mediated vasoconstriction and cardiac stimulation during a mild acidosis. The venoconstriction shifts blood centrally and this causes pulmonary congestion. Pulmonary artery pressure usually rises during acidosis. The shift of the oxygen dissociation curve to the right due to the acidosis occurs rapidly. After 6 hours of acidosis, the red cell levels of 2,3 DPG have declined enough to shift the oxygen dissociation curve (ODC) back to normal. Acidosis is commonly said to cause hyperkalaemia by a shift of potassium out of cells. The effect on potassium levels is extremely variable and indirect effects due to the type of acidosis present are much more important. For example hyperkalaemia is due to renal failure in uraemic acidosis rather than the acidosis. Significant potassium loss du Continue reading >>

Effects Of Acidosis On Brain Capillary Endothelial Cells And Cholinergic Neurons: Relevance To Vascular Dementia And Alzheimer's Disease.

Effects Of Acidosis On Brain Capillary Endothelial Cells And Cholinergic Neurons: Relevance To Vascular Dementia And Alzheimer's Disease.

Effects of acidosis on brain capillary endothelial cells and cholinergic neurons: relevance to vascular dementia and Alzheimer's disease. Laboratory of Experimental Alzheimer's Research, Department of General Psychiatry, Innsbruck Medical University, Austria. Alzheimer's disease is a progressive brain disorder which is neuropathologically characterized by an increased number of beta-amyloid plaques, tau pathology and synapse loss. Recent research suggests that vascular pathology may be also important for the development and progression of Alzheimer's disease. It is still unknown whether there is a relation between damage of brain capillary endothelial cells (BCEC) and subsequent cholinergic cell death. The aim of this study was to examine the effects of acidosis on cell death of BCEC and cholinergic neurons in an organotypic brain slice model. We show that BCEC were heavily damaged in medium at pH<6.6. Cholinergic neurons incubated in medium pH 6.0 degenerated within 2-3 days and were not rescued by nerve growth factor (NGF). Lactate did not affect the survival of BCEC or cholinergic neurons. Both BCEC and cholinergic cells were not affected at pH 7.4, 7.0 or 6.6. It is concluded that both endothelial cells and cholinergic neurons have a high capacity to compensate for pH changes. At a certain pH, however, the vascular and neuronal cells show the same vulnerability, indicating that a low pH is deleterious for the cerebral microenvironment. Future studies are necessary to explore whether temporary pH changes could be responsible for cerebrovascular damage and cholinergic cell death. Acidosis may play an important role in the development of vascular dementia and Alzheimer's disease. Continue reading >>

Acidosis

Acidosis

For acidosis referring to acidity of the urine, see renal tubular acidosis. "Acidemia" redirects here. It is not to be confused with Academia. Acidosis is a process causing increased acidity in the blood and other body tissues (i.e., an increased hydrogen ion concentration). If not further qualified, it usually refers to acidity of the blood plasma. The term acidemia describes the state of low blood pH, while acidosis is used to describe the processes leading to these states. Nevertheless, the terms are sometimes used interchangeably. The distinction may be relevant where a patient has factors causing both acidosis and alkalosis, wherein the relative severity of both determines whether the result is a high, low, or normal pH. Acidosis is said to occur when arterial pH falls below 7.35 (except in the fetus – see below), while its counterpart (alkalosis) occurs at a pH over 7.45. Arterial blood gas analysis and other tests are required to separate the main causes. The rate of cellular metabolic activity affects and, at the same time, is affected by the pH of the body fluids. In mammals, the normal pH of arterial blood lies between 7.35 and 7.50 depending on the species (e.g., healthy human-arterial blood pH varies between 7.35 and 7.45). Blood pH values compatible with life in mammals are limited to a pH range between 6.8 and 7.8. Changes in the pH of arterial blood (and therefore the extracellular fluid) outside this range result in irreversible cell damage.[1] Signs and symptoms[edit] General symptoms of acidosis.[2] These usually accompany symptoms of another primary defect (respiratory or metabolic). Nervous system involvement may be seen with acidosis and occurs more often with respiratory acidosis than with metabolic acidosis. Signs and symptoms that may be seen i Continue reading >>

Acidosis

Acidosis

When your body fluids contain too much acid, it’s known as acidosis. Acidosis occurs when your kidneys and lungs can’t keep your body’s pH in balance. Many of the body’s processes produce acid. Your lungs and kidneys can usually compensate for slight pH imbalances, but problems with these organs can lead to excess acid accumulating in your body. The acidity of your blood is measured by determining its pH. A lower pH means that your blood is more acidic, while a higher pH means that your blood is more basic. The pH of your blood should be around 7.4. According to the American Association for Clinical Chemistry (AACC), acidosis is characterized by a pH of 7.35 or lower. Alkalosis is characterized by a pH level of 7.45 or higher. While seemingly slight, these numerical differences can be serious. Acidosis can lead to numerous health issues, and it can even be life-threatening. There are two types of acidosis, each with various causes. The type of acidosis is categorized as either respiratory acidosis or metabolic acidosis, depending on the primary cause of your acidosis. Respiratory acidosis Respiratory acidosis occurs when too much CO2 builds up in the body. Normally, the lungs remove CO2 while you breathe. However, sometimes your body can’t get rid of enough CO2. This may happen due to: chronic airway conditions, like asthma injury to the chest obesity, which can make breathing difficult sedative misuse deformed chest structure Metabolic acidosis Metabolic acidosis starts in the kidneys instead of the lungs. It occurs when they can’t eliminate enough acid or when they get rid of too much base. There are three major forms of metabolic acidosis: Diabetic acidosis occurs in people with diabetes that’s poorly controlled. If your body lacks enough insulin, keton Continue reading >>

Effects Of Acidosis And Alkalosis On Hypoxic Pulmonary Vasoconstriction In Dogs.

Effects Of Acidosis And Alkalosis On Hypoxic Pulmonary Vasoconstriction In Dogs.

Effects of acidosis and alkalosis on hypoxic pulmonary vasoconstriction in dogs. Laboratory of Cardiovascular and Respiratory Physiology, Erasme University Hospital, Brussels, Belgium. Am J Physiol. 1990 Feb;258(2 Pt 2):H347-53. We studied the effects of metabolic and respiratory acidosis (pH 7.20) and alkalosis (pH 7.60) on pulmonary vascular tone in 32 pentobarbital-anesthetized dogs ventilated with hyperoxia (inspired oxygen fraction, FIO2 0.40) and with hypoxia (FIO2 0.10). Ventilation, pulmonary capillary wedge pressure (Ppw), and cardiac output (3 l.min-1.m-2) were maintained constant to prevent passive changes in pulmonary arterial pressure (Ppa). Metabolic acidosis and alkalosis were induced with HCl (2 mmol.kg-1.h-1) and NaHCO3-Na2CO3 (5 mmol.kg-1.h-1) infusions, respectively, and respiratory acidosis and alkalosis by modifying the inspiratory CO2 fraction. The hypoxia-induced rise in Ppa-Ppw gradient increased from 5 to 9 mmHg in metabolic acidosis (P less than 0.001), decreased from 6 to 1 mmHg in metabolic alkalosis (P less than 0.001), remained unchanged in respiratory acidosis, and decreased from 5 to 2 mmHg in respiratory alkalosis (P less than 0.001). Linear relationships were found between pH and Ppa-Ppw gradients. These data indicate that in intact anesthetized dogs, metabolic acidosis and alkalosis, respectively, enhance and reverse hypoxic pulmonary vasoconstriction (HPV). Respiratory acidosis did not affect HPV and respiratory alkalosis blunted HPV, which suggests an pH-independent vasodilating effect of CO2. Continue reading >>

Effects Of Metabolic And Respiratory Acidosis On Bone.

Effects Of Metabolic And Respiratory Acidosis On Bone.

1. Curr Opin Nephrol Hypertens. 1993 Jul;2(4):588-96. Effects of metabolic and respiratory acidosis on bone. (1)University of Rochester School of Medicine and Dentistry, Strong Memorial Hospital, NY 14642. Acidosis had long been thought to influence the bone mineral; however, there was little direct evidence to support this impression. When neonatal mouse calvariae are cultured for 3 hours in medium with a reduced bicarbonate concentration, amodel of acute metabolic acidosis, there is net calcium efflux from bone inaddition to a net influx of protons into bone lessening the magnitude of theacidosis. The protons appear to exchange for sodium and potassium on the bonesurface. In these acute experiments, the calcium efflux appears to be due tomobilization of carbonated apatite through an alteration in the physicochemicaldriving forces for bone accretion and dissolution. In more chronic cultures(greater than 48 hours) metabolic acidosis induces calcium efflux by stimulating osteoclastic bone resorption and inhibiting osteoblastic bone formation. Whencalvariae are cultured acutely in medium with an elevated partial pressure ofcarbon dioxide, a model of respiratory acidosis, there is also calcium efflux,but at the same decrement in pH the magnitude is far less than that observedduring metabolic acidosis. There does not appear to be any measurable influx ofprotons into bone, and during chronic cultures there is no measurable calciumefflux. Thus, acidosis influences the bone mineral; however, for the samedecrement in pH there is a marked difference in the response of bone to models ofmetabolic and respiratory acidosis. Continue reading >>

Effects Of Acidosis On Rat Muscle Metabolism And Performance During Heavy Exercise.

Effects Of Acidosis On Rat Muscle Metabolism And Performance During Heavy Exercise.

Effects of acidosis on rat muscle metabolism and performance during heavy exercise. Am J Physiol. 1985 Mar;248(3 Pt 1):C337-47. The metabolism and performance of a perfused rat hindquarter preparation was examined during heavy exercise in three conditions: control (C), metabolic acidosis (MA, decreased bicarbonate concentration), and respiratory acidosis (RA, increased CO2 tension). A one-pass system was used to perfuse the hindquarters for 30 min at rest and 20 min during tetanic stimulation via the sciatic nerve. The isometric tension generated by the gastrocnemius-plantaris-soleus muscle group was recorded, and biopsies were taken pre- and postperfusion. Initial isometric tensions were similar in all conditions, but the rate of tension decay was largest in acidosis; the 5-min tensions for C, MA, and RA were 1,835 +/- 63, 1,534 +/- 63, and 1,434 +/- 73 g, respectively. O2 uptake in C was greater than in MA and RA (23.4 +/- 1.3 vs. 17.0 +/- 1.4 and 16.5 +/- 2.3 mumol X min-1), paralleling the tension findings. Hindquarter lactate release was greatest in C, least in MA, and intermediate in RA. Acidosis resulted in less muscle glycogen utilization and lactate accumulation than during control. Muscle creatine phosphate utilization and ATP levels were unaffected by acidosis. Acidosis decreased the muscle's ability to generate isometric tension and depressed both aerobic and anaerobic metabolism. During stimulation in this model lactate left the muscle mainly as a function of the production rate, although a low plasma bicarbonate concentration at pH 7.15 depressed muscle lactate release. Continue reading >>

Respiratory Acidosis: Causes, Symptoms, And Treatment

Respiratory Acidosis: Causes, Symptoms, And Treatment

Respiratory acidosis develops when air exhaled out of the lungs does not adequately exchange the carbon dioxide formed in the body for the inhaled oxygen in air. There are many conditions or situations that may lead to this. One of the conditions that can reduce the ability to adequately exhale carbon dioxide (CO2) is chronic obstructive pulmonary disease or COPD. CO2 that is not exhaled can shift the normal balance of acids and bases in the body toward acidic. The CO2 mixes with water in the body to form carbonic acid. With chronic respiratory acidosis, the body partially makes up for the retained CO2 and maintains acid-base balance near normal. The body's main response is an increase in excretion of carbonic acid and retention of bicarbonate base in the kidneys. Medical treatment for chronic respiratory acidosis is mainly treatment of the underlying illness which has hindered breathing. Treatment may also be applied to improve breathing directly. Respiratory acidosis can also be acute rather than chronic, developing suddenly from respiratory failure. Emergency medical treatment is required for acute respiratory acidosis to: Regain healthful respiration Restore acid-base balance Treat the causes of the respiratory failure Here are some key points about respiratory acidosis. More detail and supporting information is in the main article. Respiratory acidosis develops when decreased breathing fails to get rid of CO2 formed in the body adequately The pH of blood, as a measure of acid-base balance, is maintained near normal in chronic respiratory acidosis by compensating responses in the body mainly in the kidney Acute respiratory acidosis requires emergency treatment Tipping acid-base balance to acidosis When acid levels in the body are in balance with the base levels in t Continue reading >>

Effects Of Clinically Relevant Acute Hypercapnic And Metabolic Acidosis On The Cardiovascular System: An Experimental Porcine Study

Effects Of Clinically Relevant Acute Hypercapnic And Metabolic Acidosis On The Cardiovascular System: An Experimental Porcine Study

Effects of clinically relevant acute hypercapnic and metabolic acidosis on the cardiovascular system: an experimental porcine study Stengl et al.; licensee BioMed Central Ltd.2013 Hypercapnic acidosis (HCA) that accompanies lung-protective ventilation may be considered permissive (a tolerable side effect), or it may be therapeutic by itself. Cardiovascular effects may contribute to, or limit, the potential therapeutic impact of HCA; therefore, a complex physiological study was performed in healthy pigs to evaluate the systemic and organ-specific circulatory effects of HCA, and to compare them with those of metabolic (eucapnic) acidosis (MAC). In anesthetized, mechanically ventilated and instrumented pigs, HCA was induced by increasing the inspired fraction of CO2 (n = 8) and MAC (n = 8) by the infusion of HCl, to reach an arterial plasma pH of 7.1. In the control group (n = 8), the normal plasma pH was maintained throughout the experiment. Hemodynamic parameters, including regional organ hemodynamics, blood gases, and electrocardiograms, were measured in vivo. Subsequently, isometric contractions and membrane potentials were recorded in vitro in the right ventricular trabeculae. HCA affected both the pulmonary (increase in mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance (PVR)) and systemic (increase in mean arterial pressure (MAP), decrease in systemic vascular resistance (SVR)) circulations. Although the renal perfusion remained unaffected by any type of acidosis, HCA increased carotid, portal, and, hence, total liver blood flow. MAC influenced the pulmonary circulation only (increase in MPAP and PVR). Both MAC and HCA reduced the stroke volume, which was compensated for by an increase in heart rate to maintain (MAC), or even increase (HCA), Continue reading >>

Metabolic Acidosis: Pathophysiology, Diagnosis And Management: Adverse Effects Of Metabolic Acidosis

Metabolic Acidosis: Pathophysiology, Diagnosis And Management: Adverse Effects Of Metabolic Acidosis

Recommendations for the treatment of acute metabolic acidosis Gunnerson, K. J., Saul, M., He, S. & Kellum, J. Lactate versus non-lactate metabolic acidosis: a retrospective outcome evaluation of critically ill patients. Crit. Care Med. 10, R22-R32 (2006). Eustace, J. A., Astor, B., Muntner, P M., Ikizler, T. A. & Coresh, J. Prevalence of acidosis and inflammation and their association with low serum albumin in chronic kidney disease. Kidney Int. 65, 1031-1040 (2004). Kraut, J. A. & Kurtz, I. Metabolic acidosis of CKD: diagnosis, clinical characteristics, and treatment. Am. J. Kidney Dis. 45, 978-993 (2005). Kalantar-Zadeh, K., Mehrotra, R., Fouque, D. & Kopple, J. D. Metabolic acidosis and malnutrition-inflammation complex syndrome in chronic renal failure. Semin. Dial. 17, 455-465 (2004). Kraut, J. A. & Kurtz, I. Controversies in the treatment of acute metabolic acidosis. NephSAP 5, 1-9 (2006). Cohen, R. M., Feldman, G. M. & Fernandez, P C. The balance of acid base and charge in health and disease. Kidney Int. 52, 287-293 (1997). Rodriguez-Soriano, J. & Vallo, A. Renal tubular acidosis. Pediatr. Nephrol. 4, 268-275 (1990). Wagner, C. A., Devuyst, O., Bourgeois, S. & Mohebbi, N. Regulated acid-base transport in the collecting duct. Pflugers Arch. 458, 137-156 (2009). Boron, W. F. Acid base transport by the renal proximal tubule. J. Am. Soc. Nephrol. 17, 2368-2382 (2006). Igarashi, T., Sekine, T. & Watanabe, H. Molecular basis of proximal renal tubular acidosis. J. Nephrol. 15, S135-S141 (2002). Sly, W. S., Sato, S. & Zhu, X. L. Evaluation of carbonic anhydrase isozymes in disorders involving osteopetrosis and/or renal tubular acidosis. Clin. Biochem. 24, 311-318 (1991). Dinour, D. et al. A novel missense mutation in the sodium bicarbonate cotransporter (NBCe1/ SLC4A4) Continue reading >>

Effects Of Metabolic Acidosis On Viability Of Cells Exposed To Anoxia.

Effects Of Metabolic Acidosis On Viability Of Cells Exposed To Anoxia.

1. Am J Physiol. 1985 Jul;249(1 Pt 1):C149-59. Effects of metabolic acidosis on viability of cells exposed to anoxia. The effects of metabolic acidosis were examined in isolated rat hepatocytes undersubstrate-free oxygenated or anoxic conditions. Lowering extracellular pH to 6.6 under aerobic conditions had no deleterious effects on the cells as determined bytrypan blue exclusion, lactate dehydrogenase (LDH) release, cellular K+ and Ca2+ content, and ability to increase ATP levels after nutrients and adenosine wereadded to media. Cytosolic pH was measured in aerobic cells at varyingextracellular pH using 6-carboxyfluorescein. By using values for cytosolic pHobtained in this manner together with 5,5-dimethyl[2-14C]oxazolidine-2,4-dione(DMO) distribution data, a method was derived for determining intramitochondrial pH. The pH gradient across the mitochondrial membrane was found not to changewith a decrease in extracellular pH from 7.4 to 6.9. At pH 6.9 hepatocytes wereprotected against anoxic injury as compared with cells incubated at pH 7.5 or6.6. This protection was manifested by a decrease in vital dye uptake and LDHrelease, maintenance of higher cellular K+ content, less stimulation ofrespiration with succinate, improved recovery of ATP levels after return to anoxygenated nutrient environment, and maintenance of normal cellular Ca2+ content after reoxygenation. Recovery of cellular ATP content was independent of ATPlevels, total adenine nucleotide pool, and energy charge ratio at the end of the anoxic period. Measurement of cytoplasmic pH in anaerobic cells by [14C]DMOdistribution showed progressive cellular acidification with lowering ofextracellular pH. The protective effects observed at pH 6.9 are not unique tohepatocytes since isolated renal cortical tubules expo Continue reading >>

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