title: Fuel homeostasis in the harbor seal during submerged swimming.
abstract: 1. The turnover rates and oxidation rates of plasma glucose, lactate, and free fatty acids (FFA) were measured in three harbor seals (average mass = 40 kg) at rest or during voluntary submerged swimming in a water flume at 35% (1.3 m.s-1) and 50% (2 m.s-1) of maximum oxygen consumption (MO2max). 2. For seals resting in water, the total turnover rates for glucose, lactate, and FFA were 23.2, 26.2, and 7.5 mumols.min-1.kg-1, respectively. Direct oxidation of these metabolites accounted for approximately 7%, 27%, and 33% of their turnover and 3%, 7%, and 18% of the total ATP production, respectively. 3. For swimming seals, MO2max was achieved at a drag load equivalent to a speed of 3 m.s-1 and averaged 1.85 mmol O2.min-1.kg-1, which is 9-fold greater than resting metabolism in water at 18 degrees C. 4. At 35% and 50% MO2max, glucose turnover and oxidation rates did not change from resting levels. Glucose oxidation contributed about 1% of the total ATP production during swimming. 5. At 50% MO2max, lactate turnover and anaerobic ATP production doubled, but the steady state plasma lactate concentration remained low at 1.1 mM. Lactate oxidation increased 63% but still contributed only 4% of the total ATP production. Anaerobic metabolism contributed about 1% of the total ATP production at rest and during swimming. 6. The plasma FFA concentration and turnover rate increased only 24% and 37% over resting levels, respectively, at 50% MO2max. However, the oxidation rate increased almost 3.5-fold and accounted for 85% of the turnover.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Physiological Research Laboratory, Scripps Institution of Oceanography, La Jolla, CA 92037.
authors.forename: R W
authors.initials: RW
authors.lastname: Davis
authors.forename: M A
authors.initials: MA
authors.lastname: Castellini
authors.forename: T M
authors.initials: TM
authors.lastname: Williams
authors.forename: G L
authors.initials: GL
authors.lastname: Kooyman
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000332:Aerobiosis; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004242:Diving; D004734:Energy Metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D006706:Homeostasis; D007101:Immersion / Q000503:physiopathology; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008297:Male; D010101:Oxygen Consumption; D046048:Seals, Earless / Q000378:metabolism*; D013550:Swimming
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007773:Lactates; D019344:Lactic Acid; D000255:Adenosine Triphosphate