Metabolic responses to forced dives in Pekin duck measured by indirect calorimetry and 31P-MRS.
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.
Stephenson
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Department of Zoology, University of Toronto, Ontario, Canada.
Jones
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DR
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002153:Calorimetry, Indirect; D004242:Diving; D004372:Ducks / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D009132:Muscles / Q000378:metabolism; D010477:Perfusion; D010725:Phosphocreatine / Q000378:metabolism; D010758:Phosphorus; D012146:Rest
D010725:Phosphocreatine; D010758:Phosphorus; D000255:Adenosine Triphosphate