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Amino Acids as Fates of Anoxia‐Induced Lactate Loads in the Painted Turtle
Author(s) -
Hill Craig A.,
Yarasheski Kevin E.,
Warren Daniel E.
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.760.19
Subject(s) - amino acid , alanine , valine , chemistry , biochemistry , methionine , metabolism , leucine , biology
The painted turtle is the most anoxia tolerant tetrapod known. During its over‐winter hibernation which often occurs in anoxic ponds, it is capable of accumulating lactate to greater than 200mM in the plasma alone. We sought to determine whether or not amino acid synthesis serves as a metabolic fate of the lactate carbon accumulated during anoxia and recovery following anoxia at 10°C and 20°C. We hypothesized that most amino acid synthesis would occur during the recovery following anoxia. To investigate this, a bolus of [U‐ 13 C]‐lactate tracer was delivered via an arterial catheter during the anoxia and allowed to equilibrate prior to recovery. Plasma was sampled throughout the dive and subsequent recovery, and liver, pectoralis, and ventricle were sampled at the end of anoxia and at the end of recovery. The enrichments of alanine, glycine, valine, methionine, aspartate, and glutamate in plasma samples and tissue extracts were measured using gas chromatography and mass spectrometry. Results show a clear difference between the end of anoxia versus the end of recovery following anoxia in both the plasma and in the cytosolic free amino acids. Furthermore, enrichment was significantly different in the liver versus pectoralis and ventricle. Direct enrichment of alanine as M+3 alanine from pyruvate was observed, but the remaining amino acids were primarily enriched as M+2, with less M+3 and M+4, showing that the lactate carbon persists for at least one turn of the citric acid cycle (CAC). The anaplerotic amino acids, glutamate and aspartate, were also highly enriched, indicating elevated pyruvate carboxylase activity and potentially representing an auxiliary pool for rapid replenishment of CAC intermediates when needed. Future studies include amino acid tracer experiments to investigate the specific utilization of amino acids during anoxia and particularly during recovery, as well as further investigation of the amphibolic metabolism inherent to the citric acid cycle. This work is the first of its kind, and makes a significant contribution towards the development of the turtle model for metabolic studies. Support or Funding Information This work was supported by the NIH; Dr. Daniel Warren (R15 DK097700), and the Washington University Biomedical Mass Spectrometry Research Facility (P41 GM103422, P30 DK020579, P30 DK056341).