240
AUSTEN RIGGS
necessary thermodynamic consequence of the Bohr effect ( Wyman,
1948), these bloods presumably have hemoglobins with oxygen equilibria
essentially independent of pH.
Lenfant and Johansen (1966) make the important point that blood
samples should be obtained from “free swimming undisturbed animals
with the least possible trauma.” This suggestion is given added weight
by the finding that the P,, of rabbit blood rises 2.7 mm when 100 pg
aldosterone per kilogram body weight is injected (Bauer and RathschlagSchaefer, 19s8). Of course, one cannot extrapolate from rabbit to fish,
but the observation indicates that changes in hormone balance can influence the oxygen affinity.
In sharp contrast to the dogfish, the hemoglobin of the barn-door
skate, Raja binoculata, has a large Bohr effect-in both red cells and
in solution which extends from pH 6.5 to 10.5 (Manwell, 195813). No
other hemoglobin is known which has a Bohr effect which extends over
such a range. The red cell suspension has a significantly lower oxygen
affinity than the hemoglobin solution. The largest difference between
cell and solution occurs at pH 6.5 and is smaller at higher pH. Therefore, the measured Bohr effect is larger in the red cell suspension than
in the solution when measured between pH 7.0 and 7.5. Although these
differences may be explained by the presence of allosteric substances
in the red cell, other explanations are not excluded: the two sets of
experiments were not carried out under identical conditions. The large
Bohr effect requires that at any pH above the isoelectric point the red
cell will have a lower oxygen affinity than possessed by hemoglobin in
solution at the extracellular pH.
Manwell found that the cooperativity is pH dependent: n = 1.2 at
pH 6.5 and increases to +1.6-1.7 at pH 7.5. Although this held true for
both red cell and solution from the adult, hemolysis appears to abolish
cooperativity in the embryonic hemoglobin. These curious features
strongly suggest a unique embryonic hemoglobin, but the possibility
cannot be excluded that the measured difference in oxygen affinity may
result in whole or in part from some allosteric substance.
3. TELEOSTS
The properties of the hemoglobins of teleost fishes cover an enormous
range in oxygen affinity, size of Bohr effect, and temperature dependence.
One might suppose that these variations reflect the large differences in
metabolic activity and in the available environmental oxygen, and this
appears to be generally true. However, many seeming paradoxes exist.
For example, most teleost hemoglobins have oxygen equilibria which
AUSTEN RIGGS
necessary thermodynamic consequence of the Bohr effect ( Wyman,
1948), these bloods presumably have hemoglobins with oxygen equilibria
essentially independent of pH.
Lenfant and Johansen (1966) make the important point that blood
samples should be obtained from “free swimming undisturbed animals
with the least possible trauma.” This suggestion is given added weight
by the finding that the P,, of rabbit blood rises 2.7 mm when 100 pg
aldosterone per kilogram body weight is injected (Bauer and RathschlagSchaefer, 19s8). Of course, one cannot extrapolate from rabbit to fish,
but the observation indicates that changes in hormone balance can influence the oxygen affinity.
In sharp contrast to the dogfish, the hemoglobin of the barn-door
skate, Raja binoculata, has a large Bohr effect-in both red cells and
in solution which extends from pH 6.5 to 10.5 (Manwell, 195813). No
other hemoglobin is known which has a Bohr effect which extends over
such a range. The red cell suspension has a significantly lower oxygen
affinity than the hemoglobin solution. The largest difference between
cell and solution occurs at pH 6.5 and is smaller at higher pH. Therefore, the measured Bohr effect is larger in the red cell suspension than
in the solution when measured between pH 7.0 and 7.5. Although these
differences may be explained by the presence of allosteric substances
in the red cell, other explanations are not excluded: the two sets of
experiments were not carried out under identical conditions. The large
Bohr effect requires that at any pH above the isoelectric point the red
cell will have a lower oxygen affinity than possessed by hemoglobin in
solution at the extracellular pH.
Manwell found that the cooperativity is pH dependent: n = 1.2 at
pH 6.5 and increases to +1.6-1.7 at pH 7.5. Although this held true for
both red cell and solution from the adult, hemolysis appears to abolish
cooperativity in the embryonic hemoglobin. These curious features
strongly suggest a unique embryonic hemoglobin, but the possibility
cannot be excluded that the measured difference in oxygen affinity may
result in whole or in part from some allosteric substance.
3. TELEOSTS
The properties of the hemoglobins of teleost fishes cover an enormous
range in oxygen affinity, size of Bohr effect, and temperature dependence.
One might suppose that these variations reflect the large differences in
metabolic activity and in the available environmental oxygen, and this
appears to be generally true. However, many seeming paradoxes exist.
For example, most teleost hemoglobins have oxygen equilibria which