3. CELLULAR ASPECTS OF ACTIVE TRANSPORT
161
sponse obtained with noracetylcholine 12 (noracetylcholine dodeciodide)
or pyridine-2-aldoxime dodeciodide (2-PAD). These effects are independent of Ca concentrations.
These results suggest that to be effective in changing the permeability
of the skin a detergent must bear an electric charge, its action being then
rather unspecific and perhaps localized essentially to that part of the
membrane responsible for its condenser-like properties (109a).
We have also measured the net flux of water across the skin of Rana
temporaria temporaria L. before and after application of curare and
other compounds known to affect the potential difference and the active
transport of Na. The results are shown in Table XII (108, 110).
TABLE XII
EFFECT OF CURARE ON THE POTENTIAL DIFFERENCE AND NET FLUX OF WATER
ACROSS THE ISOLATED SKIN OF Rana temporaria temporaria L.
A
Control
Curare
Net flux of
Net flux of
Δ Potential
Expt.
Time
water
Time
water
difference
No.
(hours)
Gul. cm."
2 hr."
1
)
(hours)
(μΐ. cm.
-2 hr.
-1
)
(mv.)
1
4
5
4
8
2
4
3
3.5
7
4
3
4
3
4
4
11
4
4
3
3
16
6.5
5
4
3
3.5
15
7
6
3.5
3
3.5
9
4
7
3
5
1.5
12
-9.5
8
3
4
2.5
11
-1.5
° Ringer's solution inside; Ringer at 1:10 outside. The time in hours indicates the
duration of the control or experimental periods. Δ potential difference is the maximum
variation of the potential difference observed after application of 170 jug./ml. of d-tubocurarine chloride in the outside solution. The minus sign indicates a decrease in potential
difference (110).
It can be seen that, at the concentrations used, curare consistently
enhances the net flux of water. In some instances, the flux rate is five
times that of the control although in most experiments the rate is enhanced two- to threefold. In the case of atropine sulfate or pilocarpine
chlorohydrate, we observe an increase in both net flux of water and
electrical potential difference
(106-108).
These results are consistent with the hypothesis that curare acts on
the frog skin by increasing the diameter of membrane pores. However,
it is important to note that, despite the increase in membrane permeability to water under the influence of curare, the membrane potential is not
161
sponse obtained with noracetylcholine 12 (noracetylcholine dodeciodide)
or pyridine-2-aldoxime dodeciodide (2-PAD). These effects are independent of Ca concentrations.
These results suggest that to be effective in changing the permeability
of the skin a detergent must bear an electric charge, its action being then
rather unspecific and perhaps localized essentially to that part of the
membrane responsible for its condenser-like properties (109a).
We have also measured the net flux of water across the skin of Rana
temporaria temporaria L. before and after application of curare and
other compounds known to affect the potential difference and the active
transport of Na. The results are shown in Table XII (108, 110).
TABLE XII
EFFECT OF CURARE ON THE POTENTIAL DIFFERENCE AND NET FLUX OF WATER
ACROSS THE ISOLATED SKIN OF Rana temporaria temporaria L.
A
Control
Curare
Net flux of
Net flux of
Δ Potential
Expt.
Time
water
Time
water
difference
No.
(hours)
Gul. cm."
2 hr."
1
)
(hours)
(μΐ. cm.
-2 hr.
-1
)
(mv.)
1
4
5
4
8
2
4
3
3.5
7
4
3
4
3
4
4
11
4
4
3
3
16
6.5
5
4
3
3.5
15
7
6
3.5
3
3.5
9
4
7
3
5
1.5
12
-9.5
8
3
4
2.5
11
-1.5
° Ringer's solution inside; Ringer at 1:10 outside. The time in hours indicates the
duration of the control or experimental periods. Δ potential difference is the maximum
variation of the potential difference observed after application of 170 jug./ml. of d-tubocurarine chloride in the outside solution. The minus sign indicates a decrease in potential
difference (110).
It can be seen that, at the concentrations used, curare consistently
enhances the net flux of water. In some instances, the flux rate is five
times that of the control although in most experiments the rate is enhanced two- to threefold. In the case of atropine sulfate or pilocarpine
chlorohydrate, we observe an increase in both net flux of water and
electrical potential difference
(106-108).
These results are consistent with the hypothesis that curare acts on
the frog skin by increasing the diameter of membrane pores. However,
it is important to note that, despite the increase in membrane permeability to water under the influence of curare, the membrane potential is not