Carbohydrate and amino acid metabolism in fasting and aestivating African lungfish (Protopterus dolloi).
The potential importance of carbohydrates and amino acids as fuels during periods of fasting and aestivation in the African lungfish, Protopterus dolloi, were examined. No significant decreases in tissue glycogen levels were observed following 60 days of fasting or aestivation, suggesting lungfish may undergo 'glycogen sparing'. Yet glycogenolysis may be important during aestivation based on the differing responses of two flux-generating enzymes of the glycolytic pathway, hexokinase (HK) and pyruvate kinase (PK). PK is required for glycogen breakdown whereas HK is not. HK activity is significantly down-regulated in the heart and gill tissues during aestivation, while PK activity is sustained. The significant negative correlation between the activity of HK and glucose levels in the heart of aestivating lungfish suggests HK may be regulated by glucose concentrations. There was no indication of anaerobic glycolytic flux during aestivation as lactate did not accumulate in any of the tissues examined, and no significant induction of lactate dehydrogenase (LDH)activity was observed. The increase in glutamate dehydrogenase (GDH) and aspartate aminotransferase (Asp-AT) activities in the liver of aestivating P. dolloi suggests some energy may be obtained via increased aminoacid catabolism, leading to the generation of tricarboxylic acid (TCA) cycle intermediates. These findings indicate the importance of both carbohydrate and amino acid fuel stores during aestivation in aphylogenetically ancient, air-breathing fish.
Frick
Natasha Therese
NT
Department of Integrative Biology, University of Guelph, Guelph, Ont. N1G2W1, Canada.
Bystriansky
Jason Scott
JS
Ip
Yuen Kwong
YK
Chew
Shit Fun
SF
Ballantyne
James Stuart
JS
D000349:Africa; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D050260:Carbohydrate Metabolism; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004956:Estivation / Q000502:physiology*; D005215:Fasting / Q000502:physiology*; D005399:Fishes / Q000502:physiology*; D005943:Gluconeogenesis; D006003:Glycogen / Q000097:blood; D006593:Hexokinase / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D019344:Lactic Acid / Q000097:blood; D009132:Muscles / Q000378:metabolism; D009206:Myocardium / Q000201:enzymology; D009994:Osmolar Concentration; D014867:Water / Q000378:metabolism
D000596:Amino Acids; D001786:Blood Glucose; D014867:Water; D019344:Lactic Acid; D006003:Glycogen; D007770:L-Lactate Dehydrogenase; D002950:Citrate (si)-Synthase; D006593:Hexokinase