242
M. Maffia et al.
The main characteristics of this transport system, obtained by using the
above described radioactive technique in kinetic and specificity
experiments reported elsewhere [3J, are summarized in Table 1.
Temperature Effect on Transport Systems
An investigation of the temperature effects on plasma membrane transport
systems was performed by analyzing at different temperatures, both in T.
bernacchii and A. anguilla intestine, activity of the luminal N a + -dependent
2000+----.L----.L----L..--'---'-----L.--425000
'r:::
'E
• 1500
'r:::
~ 5.. 1000
Cl
E
"6 500
E
r:::
• T. bernacchii
• A anguilla
••. ··I
~ ~.y}-V
__ --ox I
I----I
.. ~ ... ,
::::l
3
20000 Q.
3
10
15000 "0
~
!!!.
10000 ::::l,
3
~OOO :5',
O+--'--'---r--r--r---r--+D~
-5
0
5
10
15
20
25
30
temperature °C
Fig. 4. Temperature dependence of Na+- D[14C]_glucose uptake (expressed as nmoles ofDglucose x mg proteins-! x min-i) in T bernacchii and A. anguilla brush border membrane
vesicles. Left and right ordinate pertain to the Antarctic and the temperate species
respectively.
50~--L------L------L------L------~
";'r::: 40
~
0.. 30
Cl
E
~ 20
E
10
T. bemacchii
A. anguilla
O~--~----~---~-----~-----+
o
10
20
30
40
temperature °C
Fig. 5. Effect of temperature on Na+/K+-ATPase activity in T bernacchii andA. anguilla.
mD correspond to nmoles of inorganic phosphate for minute deriving from the Na+/K+ATPase cataiysed reaction.