Fig. 6.3 Sodium transfer
(as short-circuit current) across
the isolated toad (Bufo marinus)
urinary bladder in the presence
of vasotocin (L), oxytocin (e)
and mesotocin (0).
Note : Log-dose scale.
(From BENTLEY, 1969b).
5
4
01
E
0
Q
...... 3
0
Q
u 2
u
(J)
U
oS
0
10- 12
active in increasing sodium transfer across the bladder than either oxytocin or mesotocin (Fig. 6.3).
Like in the anuran skin, several other hormone preparations have been shown
to promote sodium transport across the bladder. These include insulin (HERRERA,
1965) and adrenaline (lARD et a!., 1968). Various endocrine factors may interact
in their effects on the bladder. Aldosterone can facilitate the effects of
neurohypophysial peptides (FANESTIL et a!., 1967; HANDLER, PRESTON, and ORLOFF, 1969). Aldosterone and insulin, similarly, together can produce a far greater
increase in sodium transport in vitro than either can produce alone (CRABBE and
FRANCOIS, 1967). Such endocrine interactions probably assist all such tissues to attain optimal levels of sodium transport.
Sodium reabsorption from the urinary bladder probably occurs in the urodeles
Necturus maculosus and Ambystoma tigrinum but vasotocin has not been found
to increase this (BENTLEY and HELLER, 1964). When mudpuppies are preinjected
with aldosterone their urinary bladders are subsequently found (in vitro) to have
a facilitated rate of sodium transport, though this steroid could not be shown to
have an effect when applied directly in vitro (BENTLEY, 1971 a).
Sodium reabsorption from the urine stored in the bladder could contribute to
the sodium conservation of some amphibians. If sufficient sodium were reabsorbed
this could be particularly important in aquatic species. There is, however, no definitive information available as to the relative (to other organs and in different species) physiological significance of this. Such sodium transfer, at least in anurans,
would appear to be influenced by changes in the circulating levels of aldosterone
and could also increase on occasions when vasotocin is released.
183
(as short-circuit current) across
the isolated toad (Bufo marinus)
urinary bladder in the presence
of vasotocin (L), oxytocin (e)
and mesotocin (0).
Note : Log-dose scale.
(From BENTLEY, 1969b).
5
4
01
E
0
Q
...... 3
0
Q
u 2
u
(J)
U
oS
0
10- 12
active in increasing sodium transfer across the bladder than either oxytocin or mesotocin (Fig. 6.3).
Like in the anuran skin, several other hormone preparations have been shown
to promote sodium transport across the bladder. These include insulin (HERRERA,
1965) and adrenaline (lARD et a!., 1968). Various endocrine factors may interact
in their effects on the bladder. Aldosterone can facilitate the effects of
neurohypophysial peptides (FANESTIL et a!., 1967; HANDLER, PRESTON, and ORLOFF, 1969). Aldosterone and insulin, similarly, together can produce a far greater
increase in sodium transport in vitro than either can produce alone (CRABBE and
FRANCOIS, 1967). Such endocrine interactions probably assist all such tissues to attain optimal levels of sodium transport.
Sodium reabsorption from the urinary bladder probably occurs in the urodeles
Necturus maculosus and Ambystoma tigrinum but vasotocin has not been found
to increase this (BENTLEY and HELLER, 1964). When mudpuppies are preinjected
with aldosterone their urinary bladders are subsequently found (in vitro) to have
a facilitated rate of sodium transport, though this steroid could not be shown to
have an effect when applied directly in vitro (BENTLEY, 1971 a).
Sodium reabsorption from the urine stored in the bladder could contribute to
the sodium conservation of some amphibians. If sufficient sodium were reabsorbed
this could be particularly important in aquatic species. There is, however, no definitive information available as to the relative (to other organs and in different species) physiological significance of this. Such sodium transfer, at least in anurans,
would appear to be influenced by changes in the circulating levels of aldosterone
and could also increase on occasions when vasotocin is released.
183