5. ACID-BASE BALANCE
199
ished. As a consequence, for a given pco2 less CO, can be bound chemically and the CO, combining curve will be lowered by an equivalent
amount. Likewise the position of the p H - log pco, line will be shifted
to lower pH values for a given pm2. In the medical literature a loss in
buffer base is called a “metabolic acidosis” and an increase in buffer base
is called a “metabolic alkalosis.”
A typical example for a metabolic acidosis in fish is the accumulation of lactic acid in blood and tissues after severe exercise (Black,
1958; Black et al., 1959, 1962). In the rainbow trout, for example, Black
et al. (1966a) observed an increase in blood lactate from 5.1 to 69.7 mg I %
after 15 min of strenuous exercise which would correspond to a decrease
in buffer base of 7 mEq/liter.
3. THE EFFECTS OF OXYGENATION OF HEMOGLOBIN
As seen in Fig. 7 the CO, combining power of oxygenated blood is
less than that of reduced blood. The following two factors contribute
to this change in the CO, combining curve:
( 1 ) Because of the difference in the dissociation constant between
oxyhemoglobin and hemoglobin (see below) more bicarbonate is formed
at a given pro, in a solution containing reduced hemoglobin than in a
solution containing oxygenated hemoglobin.
( 2 ) The formation of carbamino hemoglobin is more pronounced
with reduced hemoglobin than with oxygenated hemoglobin.
Both factors participate almost equally in the change of the CO,
combining curve of mammals, although there is still some controversy
about the exact quantitative relationship. The effect of the oxygenation
on the C 0 2 combining curve is one aspect of the so-called Haldane effect.
The other and more important aspect is the effect on the buffer capacity
and the pH - log pco2 line. From Eqs. (14) and (16b) it becomes immediately evident that a decrease in K must increase p or dB/dpH. The
oxygenation of hemoglobin now increases its dissociation constant appreciably. In horse hemoglobin for instance, K is changed by a factor of
about 30 (pKo,III, = 6.68, pKktl, = 7.95). Similar effects are obtained in
the blood of other mammals and also in some fish. Reduced hemoglobin,
therefore, having a lower K and a higher pK, respectively, must be a
stronger buffer substance. Since at the tissues the transfer of CO, into
the blood takes place when 0, is released from the oxyhemoglobin,
there is a simultaneous increase in the buffer capacity. The importance
of this effect is obvious: If the exchange ratio R of CO, and 0, is 0.7,
it can be assumed with the figures of pK given above that the CO, entering the blood will not cause any change in pH because of the Haldane
199
ished. As a consequence, for a given pco2 less CO, can be bound chemically and the CO, combining curve will be lowered by an equivalent
amount. Likewise the position of the p H - log pco, line will be shifted
to lower pH values for a given pm2. In the medical literature a loss in
buffer base is called a “metabolic acidosis” and an increase in buffer base
is called a “metabolic alkalosis.”
A typical example for a metabolic acidosis in fish is the accumulation of lactic acid in blood and tissues after severe exercise (Black,
1958; Black et al., 1959, 1962). In the rainbow trout, for example, Black
et al. (1966a) observed an increase in blood lactate from 5.1 to 69.7 mg I %
after 15 min of strenuous exercise which would correspond to a decrease
in buffer base of 7 mEq/liter.
3. THE EFFECTS OF OXYGENATION OF HEMOGLOBIN
As seen in Fig. 7 the CO, combining power of oxygenated blood is
less than that of reduced blood. The following two factors contribute
to this change in the CO, combining curve:
( 1 ) Because of the difference in the dissociation constant between
oxyhemoglobin and hemoglobin (see below) more bicarbonate is formed
at a given pro, in a solution containing reduced hemoglobin than in a
solution containing oxygenated hemoglobin.
( 2 ) The formation of carbamino hemoglobin is more pronounced
with reduced hemoglobin than with oxygenated hemoglobin.
Both factors participate almost equally in the change of the CO,
combining curve of mammals, although there is still some controversy
about the exact quantitative relationship. The effect of the oxygenation
on the C 0 2 combining curve is one aspect of the so-called Haldane effect.
The other and more important aspect is the effect on the buffer capacity
and the pH - log pco2 line. From Eqs. (14) and (16b) it becomes immediately evident that a decrease in K must increase p or dB/dpH. The
oxygenation of hemoglobin now increases its dissociation constant appreciably. In horse hemoglobin for instance, K is changed by a factor of
about 30 (pKo,III, = 6.68, pKktl, = 7.95). Similar effects are obtained in
the blood of other mammals and also in some fish. Reduced hemoglobin,
therefore, having a lower K and a higher pK, respectively, must be a
stronger buffer substance. Since at the tissues the transfer of CO, into
the blood takes place when 0, is released from the oxyhemoglobin,
there is a simultaneous increase in the buffer capacity. The importance
of this effect is obvious: If the exchange ratio R of CO, and 0, is 0.7,
it can be assumed with the figures of pK given above that the CO, entering the blood will not cause any change in pH because of the Haldane