AJP - Regulatory, Integrative and Comparative Physiology, Vol 242, Issue 5 434-R440, Copyright © 1982 by American Physiological Society
Cardiovascular adjustments to laboratory diving in beavers and nutria
T. McKean
Beavers (Castor canadensis) and nutria (Myocastor coypus) were anesthetized
with halothane and catheters placed in the left ventricle, aorta and
pulmonary artery, right ventricle or right atrium. The animals were
strapped to a board and following recovery from anesthesia the following
measurements were taken: regional distribution of blood flow, cardiac
output, O2 consumption, arterial and venous blood gases, and pH. The animal
was then immersed in 15-20 degrees C water for up to 2.75 min (nutria) or 4
min (beaver) and the measurements repeated. Heart rate and cardiac output
decreased by 80 and 75%, respectively. Arterial and venous oxygen partial
pressure and content fell as did pH whereas CO2 pressures rose during
diving. Oxygen consumption at rest was 124 and 102% of that predicted on
the basis of body mass for the beaver and nutria, respectively. Rate of
decline of O2 stores during diving decreased by 93% in beavers and 89% in
nutria compared to the predive value. Regional blood flow decreased to all
organs except the adrenals, heart, and lungs. Blood flow to the brain
increased during diving.
