ANTARCTIC FISH METABOLIC RESPONSES AS POTENTIAL BIOMARKERS OF ENVIRONMENTAL IMPACT
Keywords:Antarctic, Fish, Biomarkers, Metabolism, Environment
The principal objective of this review is to discuss the energy metabolism, of L-arginine, antioxidant defense and the xenobiotics of Antarctic fishes as possible markers of environmental change. With the establishment of the circumpolar current and the physical isolation of the region, Antarctic fishes evolved under stable low temperatures. The elevated endemism, low diversity, and the probable stenthermability motivated a number of studies on Antarctic fishes. The presence of enzymes with physical and chemical properties adaptaded to low temperatures was evident in various studies and fortified the cold adaptation concept of these organisms. By ratifying the Antarctica Environmental Protection Treaty (Madrid protocol), the member countries committed themselves to monitoring the environment of the region. Though, it is one of the most pristine regions of the planet, increasing human activity in Antarctica has given rise to concerns about pollution from combustion oils, heavy metals and sewage. As the energy sustainability of the tissues requires that the velocity of the ATP generator systems should be in step with the energy demand, changes in the environment would lead to elevation in the energy demand of the organisms, which in turn demanded an adjustment of the ATP synthesis velocity. In these cases the enzymatic upregulation and downregulation have been used as biomarkers of the energy metabolism. Traditionally, the antioxidant defense enzymes and the xenobiotic metabolism of fishes have been used as biomarkers to access the natural or anthropic environmental change. However, these studies must be correlated the levels of enzymes with the principal risk factors in the environmental pollution. L-arginine metabolism enzymes have been used as biomarkers of the physiological response in mammals, but there are few studies on Antarctic fishes. The central role of the amino acid L-arginine in the synthesis of nitric oxide, polyamines and as a signal in various physiological processes has drawn the attention of scientists. The tissue distribution and the isoforms distribution, along with its control via upregulation and downregulation of the arginase enzymes, nitric oxide synthase and ornithina decarboxylase in Antarctic fishes are potential biomarkers for environmental change.