130
B. Giardina et al.
decade has clearly shown that great evolutionary changes have occurred in
several enzymatic and structural proteins [9,10] allowing Antarctic fish to
sustain metabolic activities substantially comparable to those found in fish
with higher cell temperature. These molecular and cellular adaptations are
so strongly shaped for low temperatures that Antarctic fish die when water
temperature rises from -1.9 °C to +5 °C [4]. This is the lowest temperature
of heat death known for any animal and the lowest temperature at which
synthesis of heat shock proteins is induced [11].
On this basis we may say that the fitness of Antarctic fishes to their
environment is paid by an extreme degree of stenothermality and therefore
by a significant loss of biological flexibility.
Here we recall some new and some already published results trying to
give a picture of the main characteristics of the oxidative metabolism of
Antarctic fish.
Material and Methods
Specimens were collected in the vicinity of Terra Nova Bay (Ross Sea)
and of Palmer Station (Antarctica Peninsula). All the specimens were
stored at -80°C until analysis.
Mitochondria from fish liver (~15 g) were prepared, after
homogenization of tissue with a Potter-Heve1heim homogenizer, by
gradient centrifugation in H-medium (0.7 M sucrose, 0.21 M D-mannitol,
0.002 M HEPES, BSA 0.05% w/v BSA), as reported by Pedersen et al.
[12].
Aliquots of mitochondria were used to determine coenzyme Q, vitamin
E, NADH oxidase and NADH CoQ reductase. Coenzyme Q and vitamin E
were also determined on debris fraction.
Coenzyme Q was determined according to Lippa et al. [13]. Vitamin E
was measured with the method of Ericson and Soerensen [14].
The overall activity of mitochondrial respiratory chain was tested as
NADH oxidase activity as reported by Mackler [15].
Furthennore the activity of the first and third complexes of respiratory
chain was evaluated as they are more substrate specific and speciesrepresentative. The first complex was measured testing the activity of
NADH CoQ reductase with the method of Youssef [16] and the third
complex was measured testing the activity of NADH cytochrome c
reductase according to Youssef and Stiggall [17].
Mitochondrial Respiration
As centres of oxidative phosphorylation, mitochondria are critical sites of
adenosine triphosphate (ATP) production in aerobic tissues and therefore
B. Giardina et al.
decade has clearly shown that great evolutionary changes have occurred in
several enzymatic and structural proteins [9,10] allowing Antarctic fish to
sustain metabolic activities substantially comparable to those found in fish
with higher cell temperature. These molecular and cellular adaptations are
so strongly shaped for low temperatures that Antarctic fish die when water
temperature rises from -1.9 °C to +5 °C [4]. This is the lowest temperature
of heat death known for any animal and the lowest temperature at which
synthesis of heat shock proteins is induced [11].
On this basis we may say that the fitness of Antarctic fishes to their
environment is paid by an extreme degree of stenothermality and therefore
by a significant loss of biological flexibility.
Here we recall some new and some already published results trying to
give a picture of the main characteristics of the oxidative metabolism of
Antarctic fish.
Material and Methods
Specimens were collected in the vicinity of Terra Nova Bay (Ross Sea)
and of Palmer Station (Antarctica Peninsula). All the specimens were
stored at -80°C until analysis.
Mitochondria from fish liver (~15 g) were prepared, after
homogenization of tissue with a Potter-Heve1heim homogenizer, by
gradient centrifugation in H-medium (0.7 M sucrose, 0.21 M D-mannitol,
0.002 M HEPES, BSA 0.05% w/v BSA), as reported by Pedersen et al.
[12].
Aliquots of mitochondria were used to determine coenzyme Q, vitamin
E, NADH oxidase and NADH CoQ reductase. Coenzyme Q and vitamin E
were also determined on debris fraction.
Coenzyme Q was determined according to Lippa et al. [13]. Vitamin E
was measured with the method of Ericson and Soerensen [14].
The overall activity of mitochondrial respiratory chain was tested as
NADH oxidase activity as reported by Mackler [15].
Furthennore the activity of the first and third complexes of respiratory
chain was evaluated as they are more substrate specific and speciesrepresentative. The first complex was measured testing the activity of
NADH CoQ reductase with the method of Youssef [16] and the third
complex was measured testing the activity of NADH cytochrome c
reductase according to Youssef and Stiggall [17].
Mitochondrial Respiration
As centres of oxidative phosphorylation, mitochondria are critical sites of
adenosine triphosphate (ATP) production in aerobic tissues and therefore