20
Parotid 10
salivary
4
2
1
(ml min) 1
Parotid
salivary
0
secretion
e
180 (m equiv.)
0
o-O'o_ _x~o..... , x
r~, A V x
160 Parotid x~'-o~'x
....... -._.-.
r o"v
\a.
/ / (m equiv./I)
salivary
~I
""'a./ 0
Parotid
140 sodium
~
J<>( salivary
concent.
/~\
l 0
potassium
120
x - -x
\
/ ,/
content.
•
S(
y O , . - .
._._~K"
~o-R-o-:x.-,Q
.......
100
'x " , /
- - .
' x'
80
60
40
L v. Lrtusion
Aldost e rone at
10 ILg l hr d. Iso mer
l~g/hr d. Isomer
2
4
6
8
10
12
14
Hours
Fig. 3.1 Sheep Zachary (adrenally insufficient, Na+ deficit of 250 mEq). Effect of intravenous infusion of d-aldosterone on parotid salivary Na+ concentration, X - - X ; K+
concentration .A.--.A. ; and parotid salivary Na +:K-1' , 0--0. Parotid secretion rate is
shown also. (From BLAIR-WEST et al., 1967).
of saliva. These include many of the Artiodactyla, which digest their herbivorous
diet with the aid of microbial fermentation. The volume of the fluid in the digestive
tract of these animals is largely derived from the salivary glands , making up 10 to
15% of the body weight, and containing sodium equivalent to half that present
in the extracellular fluid . A physiological mechanism to limit such sequestranon
of sodium could well be vital for survival when the amounts of this ion in the body
are depleted, and its dietary availability is limited. In addition some mammals drool
saliva from the mouth when the rectal temperature is elevated in hot situations.
Such salivation has been observed in several marsupials and placentals, including
some rodents, rabbits, cats, and cattle. If this saliva is spread over the fur it may
aid in cooling. Considerable losses of electrolytes could occur in this way during
heat stress, and these could be somewhat ameliorated by ph ysiological adjustments
of the solutes that are present.
Absorption of electrolytes in the diet and reabsorption of those secreted into
the gut take place continually across the walls of the intestines. Reduced loss of
sodium in the faeces has been observed in mammals that are depleted of sodium
or that have a surfeit of aldosterone. This suggests that corticosteroids may be concerned with regulation of sodium absorption from the int estine, but in mammals
direct evidence has been difficult to obtain. COFRE and CRABBE (1965), using the
isolated colon of the toad, Bufo marinus, have demonstrated an accelerated rate
of sodium transport from the mucosal to serosal side in the presence of aldosterone.
It appears likely that such effects also occur in the mammalian gut, though for technical reasons they are more difficult to demonstrate.
94
Parotid 10
salivary
4
2
1
(ml min) 1
Parotid
salivary
0
secretion
e
180 (m equiv.)
0
o-O'o_ _x~o..... , x
r~, A V x
160 Parotid x~'-o~'x
....... -._.-.
r o"v
\a.
/ / (m equiv./I)
salivary
~I
""'a./ 0
Parotid
140 sodium
~
J<>( salivary
concent.
/~\
l 0
potassium
120
x - -x
\
/ ,/
content.
•
S(
y O , . - .
._._~K"
~o-R-o-:x.-,Q
.......
100
'x " , /
- - .
' x'
80
60
40
L v. Lrtusion
Aldost e rone at
10 ILg l hr d. Iso mer
l~g/hr d. Isomer
2
4
6
8
10
12
14
Hours
Fig. 3.1 Sheep Zachary (adrenally insufficient, Na+ deficit of 250 mEq). Effect of intravenous infusion of d-aldosterone on parotid salivary Na+ concentration, X - - X ; K+
concentration .A.--.A. ; and parotid salivary Na +:K-1' , 0--0. Parotid secretion rate is
shown also. (From BLAIR-WEST et al., 1967).
of saliva. These include many of the Artiodactyla, which digest their herbivorous
diet with the aid of microbial fermentation. The volume of the fluid in the digestive
tract of these animals is largely derived from the salivary glands , making up 10 to
15% of the body weight, and containing sodium equivalent to half that present
in the extracellular fluid . A physiological mechanism to limit such sequestranon
of sodium could well be vital for survival when the amounts of this ion in the body
are depleted, and its dietary availability is limited. In addition some mammals drool
saliva from the mouth when the rectal temperature is elevated in hot situations.
Such salivation has been observed in several marsupials and placentals, including
some rodents, rabbits, cats, and cattle. If this saliva is spread over the fur it may
aid in cooling. Considerable losses of electrolytes could occur in this way during
heat stress, and these could be somewhat ameliorated by ph ysiological adjustments
of the solutes that are present.
Absorption of electrolytes in the diet and reabsorption of those secreted into
the gut take place continually across the walls of the intestines. Reduced loss of
sodium in the faeces has been observed in mammals that are depleted of sodium
or that have a surfeit of aldosterone. This suggests that corticosteroids may be concerned with regulation of sodium absorption from the int estine, but in mammals
direct evidence has been difficult to obtain. COFRE and CRABBE (1965), using the
isolated colon of the toad, Bufo marinus, have demonstrated an accelerated rate
of sodium transport from the mucosal to serosal side in the presence of aldosterone.
It appears likely that such effects also occur in the mammalian gut, though for technical reasons they are more difficult to demonstrate.
94