436
JOHAN B. STEEN
and Steen (1968). In venous blood leaving the rete they recorded a
lower Po, the farther away from the exit of the rete it was recorded
(Fig. 11). The half-time of the change was estimated to be 10-20 sec.
This implies that the earlier estimates of venous Po, represented the
stable end value and not the Po, actually present at the exit of the rete.
In fact the Po, at that point seemed equal to or even slightly higher than
the arterial Po? which was shown not to vary with distance from the
rete (Berg and Steen, 19f33).
The matter was further studied by measurements on the rate of the
Root shifts in suspensions of eel red cells. At 23"C, the Root off-shift
(acidification and subsequent splitting off of 0,) showed a half-time
of 0.05 sec, while the reverse process, the Root on-shift, had a tl/? of
10-20 sec (Forster and Steen, 1969).
D. Present Concept of Countercurrent
Multiplication in the Rete
Blood enters the rete with arterial p H and Po, values. As it 0ows
through the rete it receives 0, and acid (CO, and H+) from the venous
blood draining the bladder. The rate of the concomitant Root off-shift
has a tlI2 of 50 msec at 23°C (Forster and Steen, 1969).
Upon entering the bladder epithelium the arterial blood has thus
become enriched in 0, and acidified. During its further circulation
through the bladder epithelium the blood receives still more lactic acid
whereby its Po2 is further increased causing 0, diffusion into the bladder.
The addition of acid probably also increases the osmotic pressure of the
plasma, causing a reduction in the physical solubility of all gases.
When the blood returns to the rete it has a lower pH and 0, content,
but a higher Po, than when it left the rete to enter the bladder. It may
also have a lower physical gas solubility. As this blood flows through
the rete, O? will diffuse according to the gradient in Po? from venous
to arterial blood. At the same time, lactic acid and CO, pass in the same
direction thus causing increasing pH in venous blood (Steen, 1963~).
The concomitant decrease of venous Po, (Root on-shift) has a t,/? of
10-20 sec. The degree to which the venous Po, changes are completed
when the blood leaves the rete will depend on the rate of blood flow.
Final equilibrium between H+ ions, Hb, and O2 is established as the blood
flows away from the rete.
Thus, as suggested by the Kuhns, 0, is concentrated by countercurrent multiplication of a Po, gradient caused by acid; however, this
JOHAN B. STEEN
and Steen (1968). In venous blood leaving the rete they recorded a
lower Po, the farther away from the exit of the rete it was recorded
(Fig. 11). The half-time of the change was estimated to be 10-20 sec.
This implies that the earlier estimates of venous Po, represented the
stable end value and not the Po, actually present at the exit of the rete.
In fact the Po, at that point seemed equal to or even slightly higher than
the arterial Po? which was shown not to vary with distance from the
rete (Berg and Steen, 19f33).
The matter was further studied by measurements on the rate of the
Root shifts in suspensions of eel red cells. At 23"C, the Root off-shift
(acidification and subsequent splitting off of 0,) showed a half-time
of 0.05 sec, while the reverse process, the Root on-shift, had a tl/? of
10-20 sec (Forster and Steen, 1969).
D. Present Concept of Countercurrent
Multiplication in the Rete
Blood enters the rete with arterial p H and Po, values. As it 0ows
through the rete it receives 0, and acid (CO, and H+) from the venous
blood draining the bladder. The rate of the concomitant Root off-shift
has a tlI2 of 50 msec at 23°C (Forster and Steen, 1969).
Upon entering the bladder epithelium the arterial blood has thus
become enriched in 0, and acidified. During its further circulation
through the bladder epithelium the blood receives still more lactic acid
whereby its Po2 is further increased causing 0, diffusion into the bladder.
The addition of acid probably also increases the osmotic pressure of the
plasma, causing a reduction in the physical solubility of all gases.
When the blood returns to the rete it has a lower pH and 0, content,
but a higher Po, than when it left the rete to enter the bladder. It may
also have a lower physical gas solubility. As this blood flows through
the rete, O? will diffuse according to the gradient in Po? from venous
to arterial blood. At the same time, lactic acid and CO, pass in the same
direction thus causing increasing pH in venous blood (Steen, 1963~).
The concomitant decrease of venous Po, (Root on-shift) has a t,/? of
10-20 sec. The degree to which the venous Po, changes are completed
when the blood leaves the rete will depend on the rate of blood flow.
Final equilibrium between H+ ions, Hb, and O2 is established as the blood
flows away from the rete.
Thus, as suggested by the Kuhns, 0, is concentrated by countercurrent multiplication of a Po, gradient caused by acid; however, this