Document Detail

Ontogeny of hypoxic modulation of cardiac performance and its allometry in the African clawed frog Xenopus laevis.
MedLine Citation:
PMID:  22752075     Owner:  NLM     Status:  Publisher    
The ontogeny of cardiac hypoxic responses, and how such responses may be modified by rearing environment, are poorly understood in amphibians. In this study, cardiac performance was investigated in Xenopus laevis from 2 to 25 days post-fertilization (dpf). Larvae were reared under either normoxia or moderate hypoxia (PO(2) = 110 mmHg), and each population was assessed in both normoxia and acute hypoxia. Heart rate (f ( h )) of normoxic-reared larvae exhibited an early increase from 77 ± 1 beats min(-1) at 2 dpf to 153 ± 1 beats min(-1) at 4 dpf, followed by gradual decreases to 123 ± 3 beats min(-1) at 25 dpf. Stroke volume (SV), 6 ± 1 nl, and cardiac output (CO), 0.8 ± 0.1 μl min(-1), at 5 dpf both increased by more than 40-fold to 25 dpf with rapid larval growth (~30-fold increase in body mass). When exposed to acute hypoxia, normoxic-reared larvae increased f ( h ) and CO between 5 and 25 dpf. Increased SV in acute hypoxia, produced by increased end-diastolic volume (EDV), only occurred before 10 dpf. Hypoxic-reared larvae showed decreased acute hypoxic responses of EDV, SV and CO at 7 and 10 dpf. Over the period of 2-25 dpf, cardiac scaling with mass showed scaling coefficients of -0.04 (f ( h )), 1.23 (SV) and 1.19 (CO), contrary to the cardiac scaling relationships described in birds and mammals. In addition, f ( h ) scaling in hypoxic-reared larvae was altered to a shallower slope of -0.01. Collectively, these results indicate that acute cardiac hypoxic responses develop before 5 dpf. Chronic hypoxia at a moderate level can not only modulate this cardiac reflex, but also changes cardiac scaling relationship with mass.
T-C Francis Pan; Warren W Burggren
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-7-3
Journal Detail:
Title:  Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology     Volume:  -     ISSN:  1432-136X     ISO Abbreviation:  -     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-7-3     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8413200     Medline TA:  J Comp Physiol B     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Developmental Integrative Biology Research Cluster, Department of Biological Sciences, University of North Texas, Denton, TX, 76203-5017, USA,
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