Piscine insights into comparisons of anoxia tolerance, ammonia toxicity, stroke and hepatic encephalopathy.
Although the number of fish species that have been studied for both hypoxia/anoxia tolerance and ammonia tolerance are few, there appears to be a correlation between the ability to survive these two insults. After establishing this correlation with examples from the literature, and after examining the role Peter Lutz played in catalyzing this convergent interest in two variables, this article explores potential mechanisms underpinning this correlation. We draw especially on the larger body of information for two human diseases with the same effected organ (brain), namely stroke and hepatic encephalopathy. While several dissimilarities exist between the responses of vertebrates to anoxia and hyperammonemia, one consistent observation in both conditions is an overactivation of NMDA receptors or glutamate neurotoxicity. We propose a glutamate excitotoxicity hypothesis to explain the correlation between ammonia and hypoxia resistance in fish. Furthermore, we suggest several experimental paths to test this hypothesis.
Walsh
Patrick J
PJ
NIEHS Marine and Freshwater Biomedical Sciences Center, Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, FL 33149, USA. pwalsh@uottawa.ca
Veauvy
Clemence M
CM
McDonald
M Danielle
MD
Pamenter
Matthew E
ME
Buck
Leslie T
LT
Wilkie
Michael P
MP
D000222:Adaptation, Physiological; D000818:Animals; D005399:Fishes / Q000502:physiology*; D006501:Hepatic Encephalopathy / Q000503:physiopathology / Q000662:veterinary*; D022124:Hyperammonemia / Q000503:physiopathology / Q000662:veterinary*; D000860:Hypoxia / Q000503:physiopathology / Q000662:veterinary*; D020521:Stroke / Q000503:physiopathology / Q000662:veterinary*