Mechanisms of acid-base regulation in the African lungfish Protopterus annectens. 2007

K M Gilmour, and R M Euverman, and A J Esbaugh, and L Kenney, and S F Chew, and Y K Ip, and S F Perry
Department of Biology and Centre for Advanced Research in Environmental Genomics, University of Ottawa, Ottawa, ON, Canada. kgilmour@uottawa.ca

African lungfish Protopterus annectens utilized both respiratory and metabolic compensation to restore arterial pH to control levels following the imposition of a metabolic acidosis or alkalosis. Acid infusion (3 mmol kg(-1) NH(4)Cl) to lower arterial pH by 0.24 units increased both pulmonary (by 1.8-fold) and branchial (by 1.7-fold) ventilation frequencies significantly, contributing to 4.8-fold and 1.9-fold increases in, respectively, aerial and aquatic CO(2) excretion. This respiratory compensation appeared to be the main mechanism behind the restoration of arterial pH, because even though net acid excretion (J(net)H(+)) increased following acid infusion in 7 of 11 fish, the mean increase in net acid excretion, 184.5+/-118.5 micromol H(+) kg(-1) h(-1) (mean +/- s.e.m., N=11), was not significantly different from zero. Base infusion (3 mmol kg(-1) NaHCO(3)) to increase arterial pH by 0.29 units halved branchial ventilation frequency, although pulmonary ventilation frequency was unaffected. Correspondingly, aquatic CO(2) excretion also fell significantly (by 3.7-fold) while aerial CO(2) excretion was unaffected. Metabolic compensation consisting of negative net acid excretion (net base excretion) accompanied this respiratory compensation, with J(net)H(+) decreasing from 88.5+/-75.6 to -337.9+/-199.4 micromol H(+) kg(-1) h(-1) (N=8). Partitioning of net acid excretion into renal and extra-renal (assumed to be branchial and/or cutaneous) components revealed that under control conditions, net acid excretion occurred primarily by extra-renal routes. Finally, several genes that are involved in the exchange of acid-base equivalents between the animal and its environment (carbonic anhydrase, V-type H(+)-ATPase and Na(+)/HCO (-)(3) cotransporter) were cloned, and their branchial and renal mRNA expressions were examined prior to and following acid or base infusion. In no case was mRNA expression significantly altered by metabolic acid-base disturbance. These findings suggest that lungfish, like tetrapods, alter ventilation to compensate for metabolic acid-base disturbances, a mechanism that is not employed by water-breathing fish. Like fish and amphibians, however, extra-renal routes play a key role in metabolic compensation.

UI MeSH Term Description Entries
D007668 Kidney Body organ that filters blood for the secretion of URINE and that regulates ion concentrations. Kidneys
D008297 Male Males
D008969 Molecular Sequence Data Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories. Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D010802 Phylogeny The relationships of groups of organisms as reflected by their genetic makeup. Community Phylogenetics,Molecular Phylogenetics,Phylogenetic Analyses,Phylogenetic Analysis,Phylogenetic Clustering,Phylogenetic Comparative Analysis,Phylogenetic Comparative Methods,Phylogenetic Distance,Phylogenetic Generalized Least Squares,Phylogenetic Groups,Phylogenetic Incongruence,Phylogenetic Inference,Phylogenetic Networks,Phylogenetic Reconstruction,Phylogenetic Relatedness,Phylogenetic Relationships,Phylogenetic Signal,Phylogenetic Structure,Phylogenetic Tree,Phylogenetic Trees,Phylogenomics,Analyse, Phylogenetic,Analysis, Phylogenetic,Analysis, Phylogenetic Comparative,Clustering, Phylogenetic,Community Phylogenetic,Comparative Analysis, Phylogenetic,Comparative Method, Phylogenetic,Distance, Phylogenetic,Group, Phylogenetic,Incongruence, Phylogenetic,Inference, Phylogenetic,Method, Phylogenetic Comparative,Molecular Phylogenetic,Network, Phylogenetic,Phylogenetic Analyse,Phylogenetic Clusterings,Phylogenetic Comparative Analyses,Phylogenetic Comparative Method,Phylogenetic Distances,Phylogenetic Group,Phylogenetic Incongruences,Phylogenetic Inferences,Phylogenetic Network,Phylogenetic Reconstructions,Phylogenetic Relatednesses,Phylogenetic Relationship,Phylogenetic Signals,Phylogenetic Structures,Phylogenetic, Community,Phylogenetic, Molecular,Phylogenies,Phylogenomic,Reconstruction, Phylogenetic,Relatedness, Phylogenetic,Relationship, Phylogenetic,Signal, Phylogenetic,Structure, Phylogenetic,Tree, Phylogenetic
D002256 Carbonic Anhydrases A family of zinc-containing enzymes that catalyze the reversible hydration of carbon dioxide. They play an important role in the transport of CARBON DIOXIDE from the tissues to the LUNG. EC 4.2.1.1. Carbonate Dehydratase,Carbonic Anhydrase,Anhydrases, Carbonic,Dehydratase, Carbonate
D005260 Female Females
D005399 Fishes A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.
D005880 Gills Paired respiratory organs of fishes and some amphibians that are analogous to lungs. They are richly supplied with blood vessels by which oxygen and carbon dioxide are exchanged directly with the environment. Gill
D006180 Proton-Translocating ATPases Multisubunit enzymes that reversibly synthesize ADENOSINE TRIPHOSPHATE. They are coupled to the transport of protons across a membrane. ATP Dependent Proton Translocase,ATPase, F0,ATPase, F1,Adenosinetriphosphatase F1,F(1)F(0)-ATPase,F1 ATPase,H(+)-Transporting ATP Synthase,H(+)-Transporting ATPase,H(+)ATPase Complex,Proton-Translocating ATPase,Proton-Translocating ATPase Complex,Proton-Translocating ATPase Complexes,ATPase, F(1)F(0),ATPase, F0F1,ATPase, H(+),Adenosine Triphosphatase Complex,F(0)F(1)-ATP Synthase,F-0-ATPase,F-1-ATPase,F0F1 ATPase,F1-ATPase,F1F0 ATPase Complex,H(+)-ATPase,H(+)-Transporting ATP Synthase, Acyl-Phosphate-Linked,H+ ATPase,H+ Transporting ATP Synthase,H+-Translocating ATPase,Proton-Translocating ATPase, F0 Sector,Proton-Translocating ATPase, F1 Sector,ATPase Complex, Proton-Translocating,ATPase Complexes, Proton-Translocating,ATPase, H+,ATPase, H+-Translocating,ATPase, Proton-Translocating,Complex, Adenosine Triphosphatase,Complexes, Proton-Translocating ATPase,F 0 ATPase,F 1 ATPase,F0 ATPase,H+ Translocating ATPase,Proton Translocating ATPase,Proton Translocating ATPase Complex,Proton Translocating ATPase Complexes,Proton Translocating ATPase, F0 Sector,Proton Translocating ATPase, F1 Sector,Triphosphatase Complex, Adenosine
D000136 Acid-Base Equilibrium The balance between acids and bases in the BODY FLUIDS. The pH (HYDROGEN-ION CONCENTRATION) of the arterial BLOOD provides an index for the total body acid-base balance. Anion Gap,Acid-Base Balance,Acid Base Balance,Acid Base Equilibrium,Anion Gaps,Balance, Acid-Base,Equilibrium, Acid-Base,Gap, Anion,Gaps, Anion

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