QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online October 21, 2004
Journal of Experimental Biology 207, 4111-4120 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01279

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Munns, S. L. Articles by Hicks, J. W. Search for Related Content PubMed PubMed Citation Articles by Munns, S. L. Articles by Hicks, J. W. Social Bookmarking                         What's this?

Elevated intra-abdominal pressure limits venous return during exercise in Varanus exanthematicus

Suzanne L. Munns^*, Lynn K. Hartzler, Albert F. Bennett and James W. Hicks

Department of Ecology and Evolutionary Biology, University of California, 321 Steinhaus Hall, Irvine, CA 92697, USA

^* Author for correspondence (e-mail: smunns{at}uci.edu)

Accepted 6 September 2004

The effects of treadmill exercise on components of the cardiovascular (venous return, heart rate, arterial blood pressure) and respiratory systems (minute ventilation, tidal volume, breathing frequency, oxygen consumption, carbon dioxide production) and intra-abdominal pressure were investigated in the Savannah monitor lizard, Varanus exanthematicus B., at 35°C. Compared with resting conditions, treadmill exercise significantly increased lung ventilation, gular pumping, intra-abdominal pressure, mean arterial blood pressure and venous return (blood flow in the post caval vein). However, venous return declines at high levels of activity, and mean arterial pressure and venous return did not attain peak values until the recovery period, immediately following activity. Elevating intra-abdominal pressure in resting lizards (via saline infusion) resulted in significant reductions in venous return when the transmural pressure of the post caval vein became negative (i.e. when intra-abdominal pressure exceeded central venous pressure). Together these results suggest that increments in intra-abdominal pressure compress the large abdominal veins and inhibit venous return. During locomotion, the physical compression of the large abdominal veins may represent a significant limitation to cardiac output and maximal oxygen consumption in lizards.

Key words: exercise, hemodynamics, intra-abdominal pressure, lizard, locomotion, oxygen consumption, reptile, venous return, ventilation

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				M. Skals, N. Skovgaard, A. S. Abe, and T. Wang Venous tone and cardiac function in the South American rattlesnake Crotalus durissus: mean circulatory filling pressure during adrenergic stimulation in anaesthetised and fully recovered animals J. Exp. Biol., October 1, 2005; 208(19): 3747 - 3759. [Abstract] [Full Text] [PDF]

				S. L. Munns, L. K. Hartzler, A. F. Bennett, and J. W. Hicks Terrestrial locomotion does not constrain venous return in the American alligator, Alligator mississippiensis J. Exp. Biol., September 1, 2005; 208(17): 3331 - 3339. [Abstract] [Full Text] [PDF]