Document Detail

The differential cardio-respiratory responses to ambient hypoxia and systemic hypoxaemia in the South American lungfish, Lepidosiren paradoxa.
MedLine Citation:
PMID:  11691604     Owner:  NLM     Status:  MEDLINE    
Lungfishes (Dipnoi) occupy an evolutionary transition between water and air breathing and possess well-developed lungs and reduced gills. The South American species, Lepidosiren paradoxa, is an obligate air-breather and has the lowest aquatic respiration of the three extant genera. To study the relative importance, location and modality of reflexogenic sites sensitive to oxygen in the generation of cardio-respiratory responses, we measured ventilatory responses to changes in ambient oxygen and to reductions in blood oxygen content. Animals were exposed to aquatic and aerial hypoxia, both separately and in combination. While aerial hypoxia elicited brisk ventilatory responses, aquatic hypoxia had no effect, indicating a primary role for internal rather than branchial receptors. Reducing haematocrit and blood oxygen content by approximately 50% did not affect ventilation during normoxia, showing that the specific modality of the internal oxygen sensitive chemoreceptors is blood PO(2) per se and not oxygen concentration. In light of previous studies, it appears that the heart rate responses and the changes in pulmonary ventilation during oxygen shortage are similar in lungfish and tetrapods. Furthermore, the modality of the oxygen receptors controlling these responses is similar to tetrapods. Because the cardio-respiratory responses and the modality of the oxygen receptors differ from typical water-breathing teleosts, it appears that many of the changes in the mechanisms exerting reflex control over cardio-respiratory functions occurred at an early stage in vertebrate evolution.
A Sanchez; R Soncini; T Wang; P Koldkjaer; E W Taylor; M L Glass
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Comparative biochemistry and physiology. Part A, Molecular & integrative physiology     Volume:  130     ISSN:  1095-6433     ISO Abbreviation:  Comp. Biochem. Physiol., Part A Mol. Integr. Physiol.     Publication Date:  2001 Nov 
Date Detail:
Created Date:  2001-11-05     Completed Date:  2002-01-25     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9806096     Medline TA:  Comp Biochem Physiol A Mol Integr Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  677-87     Citation Subset:  IM    
Department of Physiology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
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MeSH Terms
Gills / pathology,  physiology*
Heart / physiology*
Heart Rate
Myocardium / pathology
Oxygen / blood*,  metabolism
Reg. No./Substance:

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