3. CELLULAR ASPECTS OF ACTIVE TRANSPORT
169
peptidation, and so on) (119,120)
free amino acids are believed to play
an active part in the osmotic regulation of aquatic invertebrates.
To illustrate this proposition, it may be appropriate to consider the
following observations.
The osmolar concentration in inorganic ions of the muscle of marine
invertebrates is very low with respect to the concentration prevailing in
the extracellular fluid. The muscles are nevertheless in equilibrium with
the milieu interieur, in which ionic concentrations are nearly the same as
in sea water. It has thus been postulated that small organic molecules
should be found in the intracellular fluid in order to explain the osmotic
pressure observed (121). Glycine and taurine have indeed been found
in tissues of various marine invertebrates, and more recently a systematic
study of the intracellular pool of free amino acids has been undertaken in
this laboratory in relation to the problem of animal adaptation to the
aquatic life
(122-129).
If we consider Table XIII, giving the nonprotein free amino acids
found in some invertebrate muscle and blood, it can be seen that:
(a) the concentration of 15 amino acids in blood serum is generally
TABLE XIII
FREE AMINO ACID CONTENT" OF SERUM AND MUSCLE
IN VARIOUS SPECIES (122, 123)
Hirudo
Mytilus Ostrea Anodonta Sipunculus mediAmino acid
Homarus vulgaris
edulis
edulis
cygnea
nudus
cinalis
Amino acid
Serum
Muscle
«Muscle
Alanine
8.7
205
340
646. 0
8.8
116.0
8.5
Arginine
1.6
1110
415.5
66. ,6
36.5
467.0
2.0
Aspartic acid
7.0
26.6
200.4
26. .1
4.4
30.4
9.2
Glutamic acid
3.5
500
317.0
264. 0
29.4
44.8
81.6
Glycine
24.0
1510
399.0
248. 0
13.2
1300.0
11.7
Histidine
3.5
15.5
12.1
22. .9
2.5
3.5
2.1
Isoleucine
—
—
24.8
19. 2
6.3
8.1
2.6
Leucine
4.2
78.7
15.4
12 .9
3.6
3.0
5.4
Lysine
2.1
43.8
39.4
22 .0
8.2
12.9
5.0
Methionine
0.0
14.9
9.8
8 .4
0.4
2.7
0.4
Phenylalanine
0.2
16.5
9.6
8 .5
1.6
1.2
1.6
Proline
6.0
1200
29.0
166 .0
1.0
18.8
5.2
Threonine
0.0
11.9
30.5
9 .7
3.6
8.0
7.6
Tyrosine
3.3
0.0
12.7
10 .3
2.2
2.7
2.0
Valine
0.0
35
14.4
10 .8
3.3
2.5
7.9
° Values are given as milligrams per 100 gm. fresh weight.
169
peptidation, and so on) (119,120)
free amino acids are believed to play
an active part in the osmotic regulation of aquatic invertebrates.
To illustrate this proposition, it may be appropriate to consider the
following observations.
The osmolar concentration in inorganic ions of the muscle of marine
invertebrates is very low with respect to the concentration prevailing in
the extracellular fluid. The muscles are nevertheless in equilibrium with
the milieu interieur, in which ionic concentrations are nearly the same as
in sea water. It has thus been postulated that small organic molecules
should be found in the intracellular fluid in order to explain the osmotic
pressure observed (121). Glycine and taurine have indeed been found
in tissues of various marine invertebrates, and more recently a systematic
study of the intracellular pool of free amino acids has been undertaken in
this laboratory in relation to the problem of animal adaptation to the
aquatic life
(122-129).
If we consider Table XIII, giving the nonprotein free amino acids
found in some invertebrate muscle and blood, it can be seen that:
(a) the concentration of 15 amino acids in blood serum is generally
TABLE XIII
FREE AMINO ACID CONTENT" OF SERUM AND MUSCLE
IN VARIOUS SPECIES (122, 123)
Hirudo
Mytilus Ostrea Anodonta Sipunculus mediAmino acid
Homarus vulgaris
edulis
edulis
cygnea
nudus
cinalis
Amino acid
Serum
Muscle
«Muscle
Alanine
8.7
205
340
646. 0
8.8
116.0
8.5
Arginine
1.6
1110
415.5
66. ,6
36.5
467.0
2.0
Aspartic acid
7.0
26.6
200.4
26. .1
4.4
30.4
9.2
Glutamic acid
3.5
500
317.0
264. 0
29.4
44.8
81.6
Glycine
24.0
1510
399.0
248. 0
13.2
1300.0
11.7
Histidine
3.5
15.5
12.1
22. .9
2.5
3.5
2.1
Isoleucine
—
—
24.8
19. 2
6.3
8.1
2.6
Leucine
4.2
78.7
15.4
12 .9
3.6
3.0
5.4
Lysine
2.1
43.8
39.4
22 .0
8.2
12.9
5.0
Methionine
0.0
14.9
9.8
8 .4
0.4
2.7
0.4
Phenylalanine
0.2
16.5
9.6
8 .5
1.6
1.2
1.6
Proline
6.0
1200
29.0
166 .0
1.0
18.8
5.2
Threonine
0.0
11.9
30.5
9 .7
3.6
8.0
7.6
Tyrosine
3.3
0.0
12.7
10 .3
2.2
2.7
2.0
Valine
0.0
35
14.4
10 .8
3.3
2.5
7.9
° Values are given as milligrams per 100 gm. fresh weight.