Acid–base balance during hypoxic hypometabolism: selected vertebrate strategies

• Published in: Respiratory physiology & neurobiology Vol. 141; no. 3; pp. 273 - 283
• Main Author: Jackson, Donald C
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdarm Elsevier B.V 12.08.2004; Elsevier
• Subjects: Acclimatization - physiology; Acid base balance; Acid-Base Equilibrium - physiology; Anaerobiosis; Animals; Biological and medical sciences; Carbon Dioxide - blood; Cutaneous; Diving; Environment; Fishes - physiology; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Hypometabolism; Hypoxia; Hypoxia - blood; Hypoxia - metabolism; Hypoxic hypometabolism; Lactic Acid - blood; Respiration; Turtles - physiology; Vertebrates: respiratory system; Anaerobiosis; Acid base balance; Diving; Hypoxia; Respiration; Hypometabolism; Cutaneous; Hypoxic hypometabolism; Oxygen; Respiratory system; Vertebrata; Mammalia; Skin
• ISSN: 1569-9048; 1878-1519
• DOI: 10.1016/j.resp.2004.01.009

An important functional advantage of hypoxic hypometabolism is that it blunts the acid–base consequences of hypoxia. Hypoxia can lead to anaerobiosis and metabolic acidosis and, in animals that are apneic, to respiratory acidosis. A fall in blood and tissue pH is a major limiting factor in hypoxic tolerance and a variety of strategies occur in vertebrates, in concert with hypometabolism, to respond to this acid–base challenge. These include sequestering of lactic acid away from the circulating blood during the hypoxic exposure, either in underperfused tissues or in mineralized tissues, supplementing extracellular buffering by releasing bone mineral into the circulation, and utilizing alternative metabolic pathways for anaerobiosis to produce ethanol rather than lactate as the principal end-product. For submerged air-breathing ectotherms, effective cutaneous O 2 and CO 2 exchange can also allow an animal to avoid or minimize both anaerobiosis and respiratory acidosis. These responses serve to maintain a viable acid–base state in the body and to extend the time that the hypoxic stress can be endured.