AJP - Regulatory, Integrative and Comparative Physiology, Vol 263, Issue 6 1309-R1317, Copyright © 1992 by American Physiological Society
Metabolic responses to forced dives in Pekin duck measured by indirect calorimetry and 31P-MRS
R. Stephenson and D. R. Jones
Department of Zoology, University of Toronto, Ontario, Canada.
We tested the hypothesis that forced-dived ducks experience a reduction in
metabolic rate during prolonged submergence. Unidirectionally ventilated
conscious ducks were subjected to forced dives by temporarily stopping the
airflow in the ventilation system and simultaneously filling a face mask
with cold water. A typical cardiovascular response to submergence was
observed: bradycardia and maintained arterial blood pressure.
Phosphorylated metabolite concentrations in the pectoral muscle were
measured noninvasively by phosphorus magnetic resonance spectroscopy
(31P-MRS). ATP content was constant, and phosphocreatine was depleted via
the creatine kinase reaction at a rate similar to the resting rate of ATP
turnover, which was estimated to be 0.9 mumol.min-1 x g-1 in resting
perfused pectoral muscle of pentobarbital-anesthetized ducks. Oxygen from
myoglobin supplied at most 12% of the ATP required by the resting muscle
during dives. Whole animal postdive excess oxygen consumption and blood
lactic acid accumulation suggested that the shortfall in aerobic metabolism
during forced dives was compensated by an increase in anaerobic metabolism.
