Ion and Metabolite Transport Through the Intestinal Luminal Membranes of the Antarctic Fish Trematomus bernacchii
Because they live in an aquatic environment, fish are continuously challenged with preserving the internal fluid osmolality from an increase (sea water fish) or a lowering (fresh water fish) and with maintaining an invariant ion composition despite great differences from the external milieu. The intestinal, renal and gill epithelia are the main physiological structures involved in these homeostatic processes since with their passive and active transport mechanisms they maintain ion concentrations, organic metabolites and H2O in the physiological range. In particular the intestinal epithelium is a selective barrier that controls ion and water absorption from sea water introduced into the gut and accomplishes the uptake of nutrients and metabolites needed for life and growth. Transport phenomena, either active or passive, through morphologically and functionally polarized cells of this epithelium are regulated by the components of their apical and basolateral plasma membranes such as lipids (phospholipids and cholesterol) and protein (enzymatic and transport proteins). Because fishes are essentially ectothermic animals, all these components are affected by the environmental temperature, the main effects being on membrane fluidity, permeability, and protein activity.
KeywordsBrush Border Membrane Vesicle Antarctic Fish Fresh Water Fish Intestinal Membrane Metabolite Transport
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