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Oxygen transfer during aerobic exercise in a varanid lizard Varanus mertensi is limited by the circulation

Frappell, P., Schultz, Timothy J. and Christian, Keith A. (2002). Oxygen transfer during aerobic exercise in a varanid lizard Varanus mertensi is limited by the circulation. Journal of Experimental Biology,205(17):2725-2736.

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Title Oxygen transfer during aerobic exercise in a varanid lizard Varanus mertensi is limited by the circulation
Author Frappell, P.
Schultz, Timothy J.
Christian, Keith A.
Journal Name Journal of Experimental Biology
Publication Date 2002
Volume Number 205
Issue Number 17
ISSN 1477-9145   (check CDU catalogue open catalogue search in new window)
Start Page 2725
End Page 2736
Total Pages 12
Place of Publication Cambridge, England
Publisher The Company of Biologists
0608 - Zoology
HERDC Category C1 - Journal Article (DEST)
Abstract Oxygen transfer during sustained maximal exercise while locomoting on a treadmill at 0.33 m s(-1) was examined in a varanid lizard Varanus mertensi at 35degreesC. The rate of oxygen consumption ((V)over dot (O 2)) increased with locomotion from 3.49+/-0.75 (mean+/-S.D.) to 14.0+/-4.0 ml O-2 kg(-1) min(-1). Ventilation (V-E) increased, aided by increases in both tidal volume and frequency, in direct proportion to (V)over dot(O 2). The air convection requirement ((V)over dot(E)/(V)over dot(O 2)=27) was therefore maintained, together with arterial Pa-CO 2 and Pa-O 2. The alveolar-arterial P-O 2 difference (PA(O 2)-Pa-O 2) also remained unchanged during exercise from its value at rest, which was approximately 20 mmHg. Pulmonary diffusion for carbon monoxide (0.116+/-0.027 ml kg(-1) min(-1) mmHg(-1)) was double the value previously reported in V. exanthematicus and remained unchanged with exercise. Furthermore, exercise was associated with an increase in the arterial-venous O-2 content difference (Ca-O2-Cv(O 2)), which was assisted by a marked Bohr shift in the hemoglobin saturation curve and further unloading of venous O-2. During exercise the increase in cardiac output ((Q)over dot(tot)) did not match the increase in (V)over dot(O2) such that the blood convection requirement ((Q)over dot(tot)/(V)over dot (O 2)) decreased from the pre-exercise value of approximately 35 to 16 during exercise. Together, the results suggest that ventilation and O-2 transfer across the lung are adequate to meet the aerobic needs of V. mertensi during exercise, but the decrease in the blood convection requirement in the presence of a large arterial-venous O-2 content difference suggests that a limit in the transport of O-2 is imposed by the circulation.
Keywords exercise
oxygen consumption
oxygen transport
blood gas
breathing pattern
varanus mertensi
lung diffusion
oxygen affinity
pulmonary gas-exchange
hypaxial muscles
lung ventilation
graded activity
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