spacer gif spacer gif spacer gif spacer gif spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by SEYMOUR, R. S.
Right arrow Articles by BRADFORD, D. F.
Right arrow Search for Related Content
PubMed
Right arrow Articles by SEYMOUR, R. S.
Right arrow Articles by BRADFORD, D. F.
Journal of Experimental Biology 118,143-159 (1985)
Published by Company of Biologists 1985

Blood Gas Tensions and Acid-Base Regulation in the Salt-Water Crocodile, Crocodylus Porosus, at Rest and After Exhaustive Exercise

R. S. SEYMOUR 1, A. F. BENNETT 2, and D. F. BRADFORD 3

1 Department of Zoology, University of Adelaide, Adelaide, S.A. 5001, Australia
2 Department of Zoology, University of Adelaide, Adelaide, S.A. 5001, Australia; School of Biological Sciences, University of California, Irvine, California 92717, U.S.A.
3 Department of Zoology, University of Adelaide Adelaide, S.A. 5001, Australia

1. Salt-water crocodiles, Crocodylus porosus Schneider, were catheterized and Po2, Pco2, pH and lactate concentration ([lactate]) were measured in arterial blood during rest and after forced exhaustive activity at 30°C.

2. Gas exchange ratio (R), calculated from blood Po2 and Pco2, decreased from about 1.0 to 0.3 during resting voluntary breath-holding and indicated CO2 sequestration in the body fluids. The mean value for R in undisturbed animals was 0.6, which substantiates the hypothesis that some CO2 excretion is extrapulmonary.

3. In vitro buffer value of true plasma was -23.5±1.9 mmol HCO3-1-1 pH-1. In vivo buffer value, determined by short-term self titration with metabolic CO2, was -12.2±4.7mmolHCO3-1-1 pH-1.

4. Exhaustive activity for 5 min in laboratory animals resulted in pronounced metabolic lactacidosis: pH decreased approximately from 7.43 to 7.11 while lactate concentration increased from 1.2 to 20-30 mmoll-1. The acidosis was reduced by respiratory compensation during the first hour of recovery and by metabolic adjustments that were practically complete after the third hour. Greater acidosis (pH down to 6.4) in larger field-captured animals was resolved over a longer period.

5. During recovery, lactate and proton fluxes between the blood and other tissue were uncoupled.

6. The virtual absence of the fixed-acid Bohr effect in C. porosus blood is adaptive in large individuals because it facilitates continued O2 uptake from the lung into blood which may be acidified by as much as 1 pH unit as a result of physical activity.

Key words: Blood gases, acid-base regulation, exercise, reptile

Accepted on February 27, 1985






© The Company of Biologists Ltd 1985