Ion and Metabolite Transport Through the
Intestinal Luminal Membranes of the Antarctic
Fish Trematomus bernacchii
Michele Maffia, Raffaele Acierno, Mariella Rollo, and Carlo Storelli
Laboratory of General Physiology, Department of Biology, University of Leece,
Via Provineiale Leeee-Monteroni, 73100 Leece, Italy
Introduction
Because they live in an aquatic environment, fish are continuously
challenged with preserving the internal fluid osmolarity 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 H20 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.
Between the late Oligocene and early Miocene (about 25 million years
ago) the complete separation of Antarctica from other continents took
place [1]. After this separation, the climatic history of Antarctica shows a
constant trend of temperature decrease that has brought sea water
temperature from ~5 to ~-2 °C (present day). In this condition, all
ectothermic organisms that continued to live in Antarctic waters dealt with
the thermodynamically adverse effect of low temperature on biochemical
constraints and were able to survive in this cold environment.
Our group has been involved, for several years, in studying the
adaptation of epithelial absorbing or secreting membranes to cold [2-4].
Data presented here represent some of the results that we have collected,
using the intestine of the Antarctic teleost, Trematomus bernacchii, in the
G. di Prisco, E. Pisano, A. Clarke (Eds)
Fishes of Antarctica. A biological overview
© Springer- Verlag Italia 1998
Intestinal Luminal Membranes of the Antarctic
Fish Trematomus bernacchii
Michele Maffia, Raffaele Acierno, Mariella Rollo, and Carlo Storelli
Laboratory of General Physiology, Department of Biology, University of Leece,
Via Provineiale Leeee-Monteroni, 73100 Leece, Italy
Introduction
Because they live in an aquatic environment, fish are continuously
challenged with preserving the internal fluid osmolarity 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 H20 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.
Between the late Oligocene and early Miocene (about 25 million years
ago) the complete separation of Antarctica from other continents took
place [1]. After this separation, the climatic history of Antarctica shows a
constant trend of temperature decrease that has brought sea water
temperature from ~5 to ~-2 °C (present day). In this condition, all
ectothermic organisms that continued to live in Antarctic waters dealt with
the thermodynamically adverse effect of low temperature on biochemical
constraints and were able to survive in this cold environment.
Our group has been involved, for several years, in studying the
adaptation of epithelial absorbing or secreting membranes to cold [2-4].
Data presented here represent some of the results that we have collected,
using the intestine of the Antarctic teleost, Trematomus bernacchii, in the
G. di Prisco, E. Pisano, A. Clarke (Eds)
Fishes of Antarctica. A biological overview
© Springer- Verlag Italia 1998