Lactate distribution and metabolism during and after anoxia in the turtle, Chrysemys picta bellii.
To determine the fate of lactate during and after prolonged anoxia, 14C-labeled lactate was injected into turtles after 2 h of a 6-h submergence at 20 degrees C. 14C activities of plasma and chamber water were tested at intervals during anoxia and also in expired air during 39 h of recovery. Partitioning of label in major body compartments [extracellular fluid (ECF), intracellular fluid (ICF), and shell] and 14C activity and glycogen in selected tissues (heart, liver, and muscle) were measured after anoxia (n = 7) and after recovery (n = 6). Shell 14C and [lactate] were extensively measured on six anoxic turtles. During anoxia all 14C remained in the animal indicating no urine production. At 6 h of anoxia 47% of recovered 14C, presumably still as lactate, was in the ECF, 27% in the ICF, and 30% in the shell. During recovery, plasma [lactate] fell from 35 to 5 meq, but surrounding water and expired air accounted for only 9 and 8%, respectively, of recovered label. The ICF portion grew to 41%, associated with a recovery in tissue glycogen. The shell still had 22% of total label. We conclude that, during recovery from anoxia, lactate is predominantly resynthesized to glycogen, and only a small fraction is directly oxidized. During anoxia, however, lactate is widely distributed in the body, and a surprisingly large and functionally significant fraction resides in the shell.
Jackson
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Department of Physiology, Brown University, Providence, Rhode Island 02912, USA.
Toney
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Okamoto
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D000818:Animals; D002245:Carbon Dioxide; D002250:Carbon Radioisotopes; D005110:Extracellular Space / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism*; D019344:Lactic Acid / Q000097:blood / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D009132:Muscles / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D012119:Respiration; D014018:Tissue Distribution; D014426:Turtles / Q000378:metabolism*
D002250:Carbon Radioisotopes; D002245:Carbon Dioxide; D019344:Lactic Acid; D006003:Glycogen