344
CHESTER JONES, CHAN, HENDERSON, AND BALL
or lesser requirements for seawater ingestion. Stresses such as temperature, shock, surgery, and other nonspecific stresses have a tendency to
stimulate drinking (Skadhauge and Maetz, 1967; Gaistkell and Chester
Jones, 1968).
A few data are available suggesting endocrine influences on drinking
and rates of absorption. The drinking rate of hypophysectomized freshwater eels is appreciably reduced, while in the seawater eel the same
operation has little or no effect. Adrenalectomy in contrast stimulates intake of fluid into the gut of freshwater eels, but at the same time the rate
of water absorption is diminished (when intestine is tested in vitro)
(Gaitskell and Chester Jones, 1968). Hirano et al. ( 1967) could not demonstrate an effect of urophysectomy on water flux across isolated intestinal
sacs, while hypophysectomy decreased the flux. They suggest that removal of a pars distalis hormone is responsible for the effect of hypophysectomy. In an extension of this work it was later concluded that ACTH
(via cortisol) acted to stimulate sodium movement across the mucosa
while the pars distalis hormone was effective in increasing water permeability (Hirano, 1967; Oide and Utida, 1967).
In vitro, there is a greater permeability to water in intestinal sacs from
marine fishes when compared to those of freshwater fishes (Sharratt et al.,
1964; Utida et al., 1967a,b). Various factors which have been implicated
in salt and water movements in other vertebrates have also been described
in preparations of teleost gut. These include AMP, ATP, UTP, and
glycerophosphate (M. W. Smith, 1964; Hollands and Smith, 1964). Some
of these have been shown to be present in greater quantities in intestines
of marine fishes than in those of freshwater species (Na-K-activated
ATPase, Oide, 1967; C1-activated alkaline phosphatase, Utida et al.,
1966; Utida and Isono, 1967; Utida, 1967). In the case of the C1-activated
phosphatase, this enzyme was shown to be diminished after hypophysectomy ( Utida et al., 1966).
The process of absorption of the ingested seawater from the mucosal
lumen appears to begin with dilution in the stomach and anterior intestine
by a passive flux of water and addition of gastric juices and by an active
uptake of sodium (H. W. Smith, 1930; Sharratt et al., 1964; Skadhauge
and Maetz, 1967). This is then followed by an active uptake of salts and
concomitant passage of water out of the lumen in the posterior intestine.
The mechanisms of uptake of the salt and water from the gut require
metabolic energy (Aull, 1966; M. W. Smith, 1964). There is the possibility of a nonosmotic flux of water under conditions of no net transport
of solute (House and Green, 1965; Utida et al., 1967b). The significance
of the in vitro preparations and aspects of endocrine control of fluxes
remains to be interpolated into actual physiology.
CHESTER JONES, CHAN, HENDERSON, AND BALL
or lesser requirements for seawater ingestion. Stresses such as temperature, shock, surgery, and other nonspecific stresses have a tendency to
stimulate drinking (Skadhauge and Maetz, 1967; Gaistkell and Chester
Jones, 1968).
A few data are available suggesting endocrine influences on drinking
and rates of absorption. The drinking rate of hypophysectomized freshwater eels is appreciably reduced, while in the seawater eel the same
operation has little or no effect. Adrenalectomy in contrast stimulates intake of fluid into the gut of freshwater eels, but at the same time the rate
of water absorption is diminished (when intestine is tested in vitro)
(Gaitskell and Chester Jones, 1968). Hirano et al. ( 1967) could not demonstrate an effect of urophysectomy on water flux across isolated intestinal
sacs, while hypophysectomy decreased the flux. They suggest that removal of a pars distalis hormone is responsible for the effect of hypophysectomy. In an extension of this work it was later concluded that ACTH
(via cortisol) acted to stimulate sodium movement across the mucosa
while the pars distalis hormone was effective in increasing water permeability (Hirano, 1967; Oide and Utida, 1967).
In vitro, there is a greater permeability to water in intestinal sacs from
marine fishes when compared to those of freshwater fishes (Sharratt et al.,
1964; Utida et al., 1967a,b). Various factors which have been implicated
in salt and water movements in other vertebrates have also been described
in preparations of teleost gut. These include AMP, ATP, UTP, and
glycerophosphate (M. W. Smith, 1964; Hollands and Smith, 1964). Some
of these have been shown to be present in greater quantities in intestines
of marine fishes than in those of freshwater species (Na-K-activated
ATPase, Oide, 1967; C1-activated alkaline phosphatase, Utida et al.,
1966; Utida and Isono, 1967; Utida, 1967). In the case of the C1-activated
phosphatase, this enzyme was shown to be diminished after hypophysectomy ( Utida et al., 1966).
The process of absorption of the ingested seawater from the mucosal
lumen appears to begin with dilution in the stomach and anterior intestine
by a passive flux of water and addition of gastric juices and by an active
uptake of sodium (H. W. Smith, 1930; Sharratt et al., 1964; Skadhauge
and Maetz, 1967). This is then followed by an active uptake of salts and
concomitant passage of water out of the lumen in the posterior intestine.
The mechanisms of uptake of the salt and water from the gut require
metabolic energy (Aull, 1966; M. W. Smith, 1964). There is the possibility of a nonosmotic flux of water under conditions of no net transport
of solute (House and Green, 1965; Utida et al., 1967b). The significance
of the in vitro preparations and aspects of endocrine control of fluxes
remains to be interpolated into actual physiology.