title: Tissue glycogen and extracellular buffering limit the survival of red-eared slider turtles during anoxic submergence at 3 degrees C.
abstract: The goal of this study was to identify the factors that limit the survival of the red-eared slider turtle Trachemys scripta during long-term anoxic submergence at 3 degrees C. We measured blood acid-base status and tissue lactate and glycogen contents after 13, 29, and 44 d of submergence from ventricle, liver, carapace (lactate only), and four skeletal muscles. We also measured plasma Ca(2+), Mg(2+), Na(+), K(+), Cl(-), inorganic phosphate (P(i)), lactate, and glucose. After 44 d, one of the six remaining turtles died, while the other turtles were in poor condition and suffered from a severe acidemia (blood pH = 7.09 from 7.77) caused by lactic acidosis (plasma lactate 91.5 mmol L(-1)). An initial respiratory acidosis attenuated after 28 d. Lactate rose to similar concentrations in ventricle and skeletal muscle (39.3-46.1 micromol g(-1)). Liver accumulated the least lactate (21.8 micromol g(-1)), and carapace accumulated the most lactate (68.9 micromol g(-1)). Plasma Ca(2+) and Mg(2+) increased significantly throughout submergence to levels comparable to painted turtles at a similar estimated lactate load. Glycogen depletion was extensive in all tissues tested: by 83% in liver, by 90% in ventricle, and by 62%-88% in muscle. We estimate that the shell buffered 69.1% of the total lactate load, which is comparable to painted turtles. Compared with painted turtles, predive tissue glycogen contents and plasma HCO(-)(3) concentrations were low. We believe these differences contribute to the poorer tolerance to long-term anoxic submergence in red-eared slider turtles compared with painted turtles.
authors.affiliation: Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI 02912, USA.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Warren
authors.forename: Scott A
authors.initials: SA
authors.lastname: Reese
authors.forename: Donald C
authors.initials: DC
authors.lastname: Jackson
mesh_terms: D000136:Acid-Base Equilibrium; D000818:Animals; D002021:Buffers; D003080:Cold Temperature; D045604:Extracellular Fluid / Q000737:chemistry* / Q000502:physiology; D006003:Glycogen / Q000378:metabolism*; D006352:Heart Ventricles / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism; D013997:Time Factors; D014426:Turtles / Q000097:blood / Q000502:physiology*
chemical_list: D002021:Buffers; D019344:Lactic Acid; D006003:Glycogen