Physiology Comparative Aspects of Extracellular Acid-Base Balance

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Comparative Aspects of Extracellular Acid-Base Balance
by J.P. Truchot



Series: Zoophysiology (Volume 20)
Pages: 248
Publisher: ---
Edition: 1st ed., 1987
Language: English
ISBN-10: 364283132X
ISBN-13: 978-3-642-83132-4

Description

Interest in comparative acid-base physiology has considerably grown during last decades even in the absence of major technical or conceptual advances. This is firstly because it has become clear that the extracellular acid-base state reflects the performance of many exchange functions at the organism level: respiration and ventilation of the gas exchange surfaces, metab­ olism, iono-and osmoregulation. Such functions are much in­ fluenced by ambient conditions, and the measurement of acid­ base parameters thus provides useful information about the organism's responses to environmental challenges. Secondly, many processes at the molecular level are now known to be pH­ sensitive, and acid-base regulation thus appears to be a major requirement for the functional integrity of cells and organisms. How extracellular acid-base balance can be maintained in a wide variety of animals living in different conditions is the sub­ ject of this book. The approach is comparative and environ­ mental throughout. All body fluids share similar buffer proper­ ties, and common physicochemical principles apply to any acid­ base system. However, in accord with differing designs and con­ straints along animal evolution, varying effector organs and mechanisms are at work to maintain an appropriate acid-base state in the organism. Particular emphasis is placed on the fun­ damental differences between water and air breathers and on the acid-base and respiratory problems arising at the transition from an aquatic to a terrestrial life. Also the complex array of factors influencing the acid-base state in water-dwelling animals is thoroughly discussed.

1. General Properties of Water and Body Fluids as Acid-Base Systems.- 1.1 Definition of an Acid-Base System.- 1.2 Components of Physiological Acid-Base Systems.- 1.2.1 Water, Hydrogen, and Hydroxyl Ions, and the Concepts of Neutrality, Acidity, and Alkalinity.- 1.2.2 Strong Ions.- 1.2.3 Weak Acids, Conjugate Bases, and Buffering.- 1.3 Physicochemical Constraints in Acid-Base Systems.- 1.3.1 Conservation of Mass.- 1.3.2 Law of Mass Action.- 1.3.3 Electrical Neutrality and the Concept of “Strong Ion Difference”.- 1.4 Dependent and Independent Variables in Physiological Acid-Base Systems.- 1.5 Titration Behavior of Acid-Base Systems.- 1.5.1 Titration by Changes of PCO2 at Constant [SID].- 1.5.2 Titration Involving [SID] Changes.- 1.5.3 Other Types of Titrations.- 1.5.3.1 Changes of Concentration of Noncarbonic Buffers.- 1.5.3.2 Changes of Dissociation Constants in a Multicomponent Buffer System.- 2. Methodological Approaches and Problems.- 2.1 Data Acquisition: The Description of the Acid-Base State.- 2.1.1 General Principles.- 2.1.2 Measurements.- 2.1.3 Calculations.- 2.2 Interpretation of the Data: “Normal” State, Disturbances, Compensations.- 2.2.1 Problems of Definition of a “Normal” Acid-Base State.- 2.2.2 Distinguishing Passive Disturbances and Physiologically Controlled Adjustments.- 2.3 Specific Methods to be Used in Aquatic Animals.- 2.3.1 Control of Water PCO2 and Acid-Base Balance.- 2.3.2 Methods for Studying Intercompartmental Acid-Base Movements.- 2.4 Some Other Specific Problems and Limitations.- 2.4.1 Compartimentalization of Extracellular Acid-Base Systems.- 2.4.2 Equilibrium and Disequilibrium Values.- 3. Extracellular Acid-Base Status and the Nature of the Respiratory Medium.- 3.1 Extracellular pH, PCO2, and [HCO?3] in Water Breathers and Air Breathers.- 3.2 Extracellular Acid-Base Balance in Bimodal Breathers.- 3.3 Extracellular Acid-Base Balance During the Transition from Water to Air Breathing.- 3.3.1 Increased Air Breathing at High Ambient Temperature.- 3.3.2 Increased Air Breathing in Hypoxic Water.- 3.3.3 Complete Transition to Air Breathing: Lungfishes.- 3.3.4 Complete Transition to Air Breathing: Intertidal Animals.- 3.3.5 Ontogenetic Transition to Air Breathing.- 4. Acid-Base Balance and Respiratory Gases in the Ambient Medium.- 4.1 Natural Variations of O2 and CO2 in Ambient Media.- 4.1.1 Air.- 4.1.2 Water.- 4.2 Extracellular Acid-Base Balance and the Oxygenation of the Ambient Medium.- 4.2.1 Water Breathers.- 4.2.2 Air Breathers.- 4.3 Extracellular Acid-Base Balance as a Function of Ambient PCO2.- 4.3.1 Air Breathers.- 4.3.2 Water Breathers.- 4.4 Extracellular Acid-Base Balance During Combined Changes of Ambient PO2 and PCO2.- 5. Extracellular Acid-Base Balance in Aquatic Animals as a Function of the Ionic Composition and the Acid-Base Balance of the Ambient Water.- 5.1 Extracellular Acid-Base State and the Salinity of the Ambient Water.- 5.2 Extracellular Acid-Base Balance and the Concentration of Certain Ions in Freshwater.- 5.3 Extracellular Acid-Base Balance and the Acid-Base State of Ambient Water.- 5.4 Extracellular Acid-Base Disturbances in Acid Waters.- 5.5 An Overview of Ambient Factors Affecting Extracellular Acid-Base Balance in Aquatic Animals.- 6. Extracellular Acid-Base Balance and Body Temperature.- 6.1 Temperature and the Acid-Base State of Buffer Systems in Vitro.- 6.1.1 Physical Effect of Temperature on Weak Acid Dissociation.- 6.1.2 Extracellular Fluids in Vitro at Variable Temperature.- 6.1.3 Binary Buffer Models.- 6.1.4 Application to Peripheral Blood in Homeotherms.- 6.2 Normal Extracellular pH at Variable Body Temperature in Poikilotherms.- 6.2.1 Historical Account.- 6.2.2 In Vivo pH vs. Body Temperature.- 6.2.3 What Extracellular Acid-Base Variable is Under Physiological Control in Ectotherms?.- 6.3 In Vivo Variations of the Carbonic System with Body Temperature.- 6.3.1 General Considerations.- 6.3.2 Air-Breathing Ectotherms.- 6.3.3 Water Breathers.- 6.4 Significance of the Extracellular pH-Body Temperature Relationship: a Critical Evaluation.- 7. Comparative Physiology and Evolution of Acid-Base Regulatory Mechanisms.- 7.1 Buffering of ECF Acid and Base Loads.- 7.1.1 Physicochemical Buffering Capacity of Extracellular Fluids.- 7.1.2 Buffering by Mineralized Tissues.- 7.1.3 Buffering of ECF by Cellular Buffers.- 7.2 Mechanisms and Organ Systems Involved in Excretion of Acid or Base Loads.- 7.2.1 Branchial Mechanisms.- 7.2.1.1 Branchial Acid-Base Fluxes.- 7.2.1.2 The Ammonia Mechanism.- 7.2.1.3 Ionic Mechanisms.- 7.2.1.4 The Role of Carbonic Anhydrase.- 7.2.2 The Amphibian Skin.- 7.2.3 Renal Mechanisms.- 7.2.3.1 Basic Mechanisms of Renal Acid Excretion.- 7.2.3.2 Renal Responses to Acid-Base Disturbances.- 7.2.4 Respiratory Mechanisms.- 7.2.4.1 Terrestrial Vertebrates.- 7.2.4.2 Aquatic Animals.- 7.2.4.3 Respiratory Regulation of Acid-Base Balance During Temperature Changes.- 7.3 Comparative Physiology of Acid-Base Regulation: An Evolutionary Overview.- 8. Extracellular Acid-Base Balance in Some Specific Physiological Situations.- 8.1 Muscular Activity.- 8.2 Panting.- 8.3 Diving.- 8.4 Hibernation.- 8.5 Miscellaneous.- 8.5.1 Acid-Base Balance of the Avian Embryo.- 8.5.2 The Laying Hen.- 8.5.3 The Crustacean Molting Cycle.- References.- Notes Added in Proof.- References Added in Proof.- Subject and Species Index.

 
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