title: High aerobic capacities in the skeletal muscles of pinnipeds: adaptations to diving hypoxia.
abstract: The objective was to assess the aerobic capacity of skeletal muscles in pinnipeds. Samples of swimming and nonswimming muscles were collected from Steller sea lions (Eumetopias jubatus, n = 27), Northern fur seals (Callorhinus ursinus, n = 5), and harbor seals (Phoca vitulina, n = 37) by using a needle biopsy technique. Samples were either immediately fixed in 2% glutaraldehyde or frozen in liquid nitrogen. The volume density of mitochondria, myoglobin concentration, citrate synthase activity, and beta-hydroxyacyl-CoA dehydrogenase was determined for all samples. The swimming muscles of seals had an average total mitochondrial volume density per volume of fiber of 9.7%. The swimming muscles of sea lions and fur seals had average mitochondrial volume densities of 6.2 and 8.8%, respectively. These values were 1.7- to 2.0-fold greater than in the nonswimming muscles. Myoglobin concentration, citrate synthase activity, and beta-hydroxyacyl-CoA dehydrogenase were 1.1- to 2. 3-fold greater in the swimming vs. nonswimming muscles. The swimming muscles of pinnipeds appear to be adapted for aerobic lipid metabolism under the hypoxic conditions that occur during diving.
authors: Department of Medicine, University of California at San Diego, La Jolla, California, 92092-0623, USA. skanatou@ucsd.edu
authors: S B
authors: SB
authors: Kanatous
authors: L V
authors: LV
authors: DiMichele
authors: D F
authors: DF
authors: Cowan
authors: R W
authors: RW
authors: Davis
mesh_terms: D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000222:Adaptation, Physiological; D000818:Animals; D001835:Body Weight; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004242:Diving / Q000502:physiology*; D005260:Female; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology*; D046048:Seals, Earless / Q000033:anatomy & histology / Q000502:physiology*; D016205:Sigmodontinae; D013045:Species Specificity; D013550:Swimming / Q000502:physiology
chemical_list: D015094:3-Hydroxyacyl CoA Dehydrogenases; D002950:Citrate (si)-Synthase