VARIATIONS IN THE INORGANIC CONSTITUENTS OF MIXED AND PAROTID GLAND SALIVA ACTIVATED

BY REFLEX STIMULATION IN THE DOG

BY HAMILTON BAXTER

(From the Department of Physiology, McGill University, Montreal, Canada)

(Received for publication, June 17, 1933)

It was previously found (Baxter, 1929-30, 1931) that marked variations occur in the organic matter, ash, and chlorine of the sub- maxillary and parotid saliva in normal dogs fed with different substances, as well as in the course of the secretion activated by these substances. Subsequently some of the inorganic elements of saliva both from the parotid and from the submaxillary glands of normal dogs were investigated to ascertain whether any connec- tion might exist between the type of stimulus used and the level of any given ion in the saliva. The results of this investigation are presented in this paper.

Most of the previous investigators in this field have confined themselves to acute experiments in which the salivary glands were activated by electrical stimulation of the corresponding secretory parasympathetic nerve or by intravenous injection of massive doses of pilocarpine. Werther (1886), who used both methods on dogs and rabbits, was one of the first to examine the inorganic compounds of the submaxillary and parotid saliva. He found in the case of the submaxillary and parotid glands that an increase in the rate of secretion caused a higher concentration of salts in the saliva. The saliva of each of the three salivary glands investigated contained various amounts of salts. Werther’s figures, e.g. for calcium, show that that element was almost twice as abundant in the parotid and sublingual saliva as it usually is in the blood serum. On the other hand, the amount of calcium in the submaxillary saliva was only slightly higher than the average blood serum cal- cium of the dog.

Gregersen and Ingalls (1931) have shown recently that sodium, but not potassium, in the submaxillary saliva of the dog is depend-

203

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204 Mixed and Parotid Gland Saliva

ent upon the rate of secretion resulting from chorda and pilocar- pine stimulation. De Beer and Wilson (1932), using pilocarpine as a stimulus in acute experiments on dogs, found that the total amount of carbon dioxide, calcium, and potassium is greater in the parotid saliva than in the blood serum; whereas, there was a smaller concentration of chloride and sodium in the saliva than in the serum. Intravenous injection of solutions of calcium chlo- ride and of sodium carbonate increased the concentration of the corresponding ions in the saliva. The composition of the saliva was not materially affected when concentrated solutions of sodium chloride, potassium chloride, and potassium carbonate were in- jected into the blood. To this it may be added that Clark and Shell (1927) and Clark and Levine (1927) investigated the inor- ganic constituents of human “resting” mixed saliva and of mixed saliva obtained under various dietary conditions. The ion con- centration of the saliva, they found, differed greatly from that of the plasma, and they could not show any relationship between the concentration of the inorganic constituents of the blood and the amount appearing in the saliva.

Most of the data reported above were obtained through stimu- lation of the glandular activity by artificial methods. It was recently demonstrated by myself (Baxter, 1932) that pilocarpine is not a true substitute for parasympathetic stimulation of the salivary glands. However, even electrical stimulation of a secre- tory nerve is not equivalent to the complicated process of reflex stimulation of the gland under normal conditions. It should also be remembered that each gland possesses not one but two secretory nerves. It was therefore decided to study the concentration of different inorganic compounds in the saliva of the parotid and mixed glands, when activated by various stimuli in dogs with permanent salivary fistulse. In one set of experiments the volume of the saliva secreted in a given time in response to different stim- uli was equalized as far as possible. This permitted the rate of secretion of the inorganic parts of the saliva to be estimated inde pendently of the rate of secretion of water.

Methods

Fist&e of the parotid and mixed glands were made in six normal dogs, some having double parotid fist&e and others a parotid iis-

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H. Baxter

tula and fistula of the mixed glands on the same side. Saliva was collected by Pavlov’s method. The various stimuli were given to the dog continuously for 5 minutes. The dog was always stimu- lated three times during each experiment with intervals of from 10 to 15 minutes between each stimulation. Each period of stimula- tion gave almost identical amounts of secretion. The three sam- ples were combined in order to equalize any slight differences due to factors which could not be controlled. Bread and meat powder were fed continuously from a dish during each 5 minute period. Liquid stimuli were introduced into the mouth cavity by an ingenious device used by Pavlov. A small U-shaped metal tube was attached to the skin of the dog’s jaw so that one arm of the tube lay between the buccal fold of the cheek and the teeth as far back as the last molar tooth. The other end of the tube was at- tached by Mendeleeff’s cement to the animal’s cheek and connected by a rubber tube with a syringe of 20 cc. capacity, filled with a solu- tion which had to be introduced into the mouth. By movements of the tongue and lips the stimulus was distributed throughout the mouth cavity. The psychic effect of the appliance was very slight. Pilocarpine hydrochloride was injected subcutaneously and the three samples of saliva were collected at the height of the secretory flow. De Beer and Wilson centrifuged their samples of saliva before proceeding with the analysis; in my experiments this was not done. Total solids, organic matter, and ash were determined, as well as chlorine, calcium, total phosphorus, potassium, and the acid-combining power. The total solids were determined by drying at 105” for several hours. The residue was ashed in an electric furnace in which the temperature was controlled by a rheostat. Most constant results were obtained when the platinum crucibles were placed in the furnace when it was cold, the tempera- ture being gradually raised over a period of several hours until all carbon had been eliminated. The ash was dissolved by adding 5 cc. of 0.1 N hydrochloric acid, and was made up to 20 cc. in volu- metric flasks. Aliquots were then used for the determination of calcium and potassium. Chlorine was determined by the Wilson and Ball (1928) modification of Van Slyke’s method. Calcium was determined in the ash by the Clark and Collip (1925) method, which has been slightly modified for saliva by Clark and Shell (1927). The method of Fiske and Subbarow (1925) was used for

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Mixed and Parotid Gland Saliva

the determination of phosphorus, and that of Kramer and Tisdall (1921) for potassium. The acid-combining power was determined by the method employed by Pickerel1 (1914).

EXPERIMENTAL

It is evident from an examination of Tables I and II that the saliva, from the same kind of glands, may differ not only in the quantity secreted but also in the concentration of the different ions under the same stimulus in different dogs. Even when approxi- mately the same volume of secretion was obtained from two dogs under the same stimulus, the constituents of the saliva varied. Furthermore, in the case of some dogs with double parotid fist&, although the stimulus was applied equally on both sides of the mouth cavity, the secretion from one side was greater than that from the other. This peculiarity might have been due to the different way in which each dog distributed the stimulus (solutions or bread and meat powder) about the mouth cavity by move- ments of the tongue and lips. When a liquid stimulus was in- jected on one side only, the secretion from that side was invariably greater than that from the opposite gland, a fact already known. Birukov’s (1929) investigation of asymmetrical unconditioned salivary reflexes suggests another explanation of the different re- sponses from paired salivary glands. According to him, although the endings of the sensory nerves are probably equally distributed on both sides of the mucous membrane of the mouth cavity, the number of such endings connected with the homo- and hetero- lateral salivary centers may differ in different animals. If such is indeed the case, this may explain the greater or smaller reaction of paired salivary glands to a stimulus equally distributed over the mouth cavity.

The concentration of ions in the saliva of the parotid gland (Table I) differs from that of the mixed glands (Table II). The concentration of chlorine and calcium and the acid-combining power are considerably lower in the saliva of the mixed glands as compared with the parotid saliva. No great difference could be noted in the potassium concentration of either saliva. The level of total phosphorus was almost always higher in the saliva of the mixed glands. The source of this phosphorus was not determined. At any rate it was much lower in amount than the inorganic phos-

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H. Baxter 207

phorus in dog serum (5 to 6 mg. per cent), showing that little in- organic phosphorus passes from the blood into the saliva. The acid-combining power was markedly lower in the saliva of the mixed glands (17.6 to 31.2 m.-eq.) than in that of the parotid gland (25.2 to 64.4 m.-eq.). Therefore the permeability of the secretory cells of the various salivary glands varies for the different ions.

TABLE I

Response of Parotid Gland to Various Stimuli in Diflerent Dogs

1 May 10

2 Feb. 15 3 June 22 4 Apr. 6 5 “ 15 6 June 27 7 Apr. 22 8 Feb. 19 9 Mar. 4

10 Apr. 23

11 Feb. 17 12 “ 25 13 Mar. 2 14 Feb. 20 15 Mar. 5

- T

5

-

Stimulus

Bread and meat powder

“ ‘I ‘I “

NaCl 5%

“ 5% “ 5%

HCl 0.25% “ 0.25% “ 0.25%

Meat extract 10 per cent “ “ I‘ ‘I

Milk “

Pilocarpine 2

mg.

- - - -

B

2 -- -

cc.

Ash Cl Ca

-

Per PW cent cent

Per cent

6 6.4 1.590.7E j.8:

_-

ml. m!J. Per Per cent cent

312 22.5

a” .M .d

P K 2 S! $8

--~

ma. “0. m,- Per Per cent cent eq.

1.753.149.2

3 4.! 1.520.6: ).8! 30924.4 2.563.266.2 3 3.! 1.240.51 1.7: 26525.1 1.878.156.6 3 8.! 1.220.3< 1.8: 28426.c 1.468.064.0 3 3.: 1.030.3t 1.7: 3012O.f 0.945.736.8 3 0.: 1.120.3f ).7( 30425.: 0.939.641.6 7 0.t 1.450.6t I.% 28223.t 2.056.752.0 3 8.: 1.340.4s 1.8: 29425.1 1.962.264.4 2 4.1 1.47o.g ).7! 27124.1 1.968.762.8 4 0.: 1.100.5( ).6( 29520.1 0.937.925.2

1.140.3! 1.550.8( 1.470.9: 1.300.6! 1.130.3’

1.7, I .7< 3.5, I.6 3.8

32826.t 0.763.949.6 30125.: 1.373.848.8 17023.1 91.642.4 30920.! 1.376.037.6 260 21.: 0.825.060.8

The effect of different stimuli upon the parotid glands of five dogs may be seen in Table I. Some slight variations in the ionic concentration in different samples of saliva, notwithstanding equal secretion of water, could be noted in the experiments with 5 per oent NaCl and 0.25 per cent HCI solutions and the meal of bread and meat powder (cf. Experiments 2,4, and 8 on Dog 4). It would

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208 Mixed and Parotid Gland Saliva

not be quite correct, however, to refer all these variations, small as they are, to the inevitable errors of the methods.

Interesting results were obtained on a dog with a double parotid fistula (Table III). It may be seen that the difference in the con- centration of certain ions was greater in saliva obtained by differ- ent stimuli from the parotid gland on one side than in saliva se- creted by both parotid glands in response to the same stimulus.

TABLE II

Response of Mixed Glands to Various Stimuli in Different Dogs

2 3

?5j # :a

.i Date . Stimulus a

i? i$ .$ 3 Ash Cl Ca P K s

fi sE

zi 8

= 0 a 2 :: 8 4 a - - -___--_----

ce. g$ gt gt g F; zt Fit ;:

1 May 12 2 Bread and 45.71.611.140.47 13412.7 1.566.931.2 meat powder

2 “ 13 2 I‘ “ 42.31.531.080.45 13612.2 1.670.130.4 3 “ 10 5 “ “ 61.41.380.780.60 238 9.8 1.964.326.8 4 ‘I 11 5 “ “ 62.41.410.820.58 24010.2 1.866.026.0 5 Apr. 29 2 NaCl 5% 24.80.530.190.34 98 7.4 3.048.129.2 6 May 16 2 IC 3% 10.60.440.150.29 63 7.0 2.666.321.6 7 Apr. 15 5 “ 5% 55.80.750.240.51 219 6.5 1.249.122.0 8 May 3 2 HC10.25% 35.70.810.410.40 142 8.1 2.554.832.0 9 Apr. 22 5 “ 0.25yo 63.01.190.580.61 246 8.8 2.159.623.2

10 May 18 2 Meat extract 14.20.500.210.29 58 5.8 1.583.520.0 10 cent per

11 Apr. 23 5 “ “ 48.00.820.350.47 207 7.6 2.249.717.6 12 May 17 2 Milk 7.0 1.38 1.000.38 5813.2 92.524.0

Thus one gland served as a control for the other. These small va- riations of ionic concentration in different samples of saliva might also be the result of some general condition of the animal on the day of each particular experiment (e.g. state of nutrition, panting, etc.). As de Beer and Wilson (1932) showed, the increased con- centration in the blood of calcium chloride and sodium carbonate is reflected in the composition of saliva in relation to these two ions. Besides these slight variations in the concentration of ions in saliva activated by the introduction into the mouth of the solutions of

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H. Baxter 209

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Mixed and Parotid Gland Saliva

sodium chloride, hydrochloric acid, or a meal of bread and meat powder, there were very striking differences in the secretion from the same Dog 4 (Table I) in response to meat extract (Experi- ment 11) and to pilocarpine (Experiment 15), the samples being taken at the height of the secretion, The volume of the secretion for both stimuli during the same period of time (15 minutes) was practically the same, viz. 33.8 cc. and 33.4 cc. There was an insignif- icantdifference in the concentration of phosphorus in the two sam- ples (0.7 and 0.8 mg. per cent). The acid-combining power was lower in the meat extract saliva (49.6 m.-eq.) than in the pilocarpine saliva (60.8 m.-eq.). All other ions, especially the potassium ion, were much lower in pilocarpine saliva than in meat extract saliva (Cl, 328 and 260 mg. per cent; Ca, 26.6 and 21.2 mg. per cent; K, 63.9 and 25.0 mg. per cent). Thus the two stimuli activated an equal flow of water through the glandular cells during the same period of time, but quite a different amount of inorganic substances was secreted in each case. Analogous relations may be noted if the pilocarpine secretion (Experiment 15) is compared with the secretion on bread and meat powder (Experiment 2, Dog 4).

It is interesting to compare with these data the composition of the saliva in the same Dog 4 (Table I) on milk (Experiment 14). The volume of the secretion on milk (5.1 cc.) was only about one- sixth the amount of that obtained on meat extract and pilocarpine. Nevertheless, it was not merely a diminution or increase in the concentration of ions that was to be noted in this saliva, but a special ion content, typical for the given stimulus.

The same slight variations in the ion concentration, which could not be explained by the errors of the method alone, were noted in the mixed gland saliva secreted under different stimuli (Table II, cf. e.g. Experiment 4 (meal of bread and meat powder) with Experiment 9 (0.25 per cent HCl) on Dog 5). The volume of the secretion during 15 minutes (62.4 cc. and 63.0 cc. respectively) was practically the same in both experiments. Similar results may be seen also in two experiments (Experiments 6 and 10) on Dog 2 (Table II) in which saliva was obtained by stimulation with 3 per cent NaCl, and by the introduction of 10 per cent meat extract into the mouth. On the other hand, the figures for the ion concentra- tion in the samples of saliva secreted in response to the aurne stim- ulus in approximately the same volume of water are remarkably

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H. Baxter 211

close to each other (cf. Dog. 2, Experiments 1 and 2; Dog 5, Experi- ments 3 and 4). Again, the mixed glands in response to a meal of milk produced a secretion of saliva with quite a different ionic concentration---$ Experiment 6 (3 per cent NaCl) and Experi- ment 12 (milk). The concentration of calcium and potassium was far higher in the case of milk than in the case of NaCl. This difference cannot be explained by the different rate of secretion of the saliva in the two experiments because it was insignificant. These experiments show that there are certain variations in the inorganic composition of the saliva from the parotid and mixed glands, when activated by different stimuli. These variations, which are rather small following certain stimuli and more marked under other stimuli, occur independently of the rate of secretion of the saliva.

The next problem which we investigated was the influence of the strength of the stimulus on the concentration of different ions in the saliva of the mixed and parotid glands. Only a few inves- tigators have studied the influence of the rate of secretion on the concentration of the different ions in saliva. According to Werther (1886) the concentration of water-soluble salts (NaCl, NaHCOs) rises with the increased rate of secretion of the submaxillary saliva activated by chorda tympani stimulation in the dog. The water- insoluble salts do not always follow this rule. Different relations were observed in the parotid saliva of a rabbit in which the flow was stimulated by pilocarpine. With the increase in the rate of secretion the concentration of the water-insoluble salts greatly diminished, whereas the concentration of water-soluble salts was practically unchanged. Gregersen and Ingalls (1931) showed that the sodium concentration in dog submaxillary saliva obtained under chorda or pilocarpine stimulation rose with the increase in the secretion rate, but the potassium concentration under these circumstances remained practically constant. From control experiments of de Beer and Wilson (1932) it may be seen that, when the rate of the pilocarpine salivary secretion from the dog’s right parotid gland was doubled (0.26 cc. and 0.5 cc. per minute in two consecutive samples, Samples 2 and 3, Table I), the Cl, K, and Ca concentration fell a little, whereas the Na concentration rose somewhat.

There was no mention in the literature of any determinations

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212 Mixed and Parotid Gland Saliva

of the concentration of different ions in the saliva of normal dogs obtained by stimulation of the mouth cavity with various sub- stances in solutions of different strength. In Table IV are shown experiments in which diminishing concentrations of NaCl and HCl are used to stimulate the mouth cavity in a dog with permanent flstulse of the mixed and parotid glands. The amount of fluid injected into the dog’s mouth was the same in each experiment, but the concentration varied. The experiments with the solutions of NaCl and HCl in various concentrations were performed on differ- ent days, the secretions of saliva from the mixed and parotid glands in each experiment being collected simultaneously and analyzed. Of the two stimuli employed hydrochloric acid stimulated the par- otid gland in this animal to a more profuse production of saliva than the submaxillary gland. It is interesting to note that the total ash is always lower in the saliva of the mixed glands, even when the secretory rate is the same or greater. In these experiments, as in those reported above (Table II) the values for chlorine, cal- cium, and acid-combining power were invariably lower in the sub- maxillary saliva. On the other hand, the concentrations of potas- sium and phosphorus were usually somewhat higher in the saliva of the mixed glands than in the parotid saliva, independently of the rate of secretion. As the strength of the stimulus was dimin- ished, the secretion of water was also curtailed until, as in the case of 1 per cent NaCl, the salivary flow reached an extremely low level. The concentration of organic matter and total ash also fell with the diminution of the stimulus, except in the case of 1 per cent NaCI, where only a few cc. of saliva were secreted during each 5 minute period. If the secretion is too scanty there may be some increase in the content of organic substances and other con- stituents of the saliva, because very weak impulses from the center fail to activate an adequate flow of water.

There are definite changes in the concentration of different ions in saliva obtained by stimulation of the animal with NaCl and HCl solutions of various strength. In the saliva of the mixed glands the concentration of Cl and increase of the acid-combining power depended on the rate of secretion. The potassium concentration underwent certain insignificant variations which were independent of the rate of secretion. The calcium ion remained practically constant under all conditions.

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TABL

E IV

Res

pons

e of

M

ixed

and

Paro

tid

Gla

nds

to S

timul

i of

Dec

reas

ing

Stre

ngth

(D

og

6)

Saliv

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olle

cted

du

ring

thre

e pe

riods

of

5 m

inut

es

each

, w

ith

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rval

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n ea

ch

stim

ulus

va

ryin

g fro

m

10 t

o 15

m

inut

es.

- s?

j 8 w

- 1 2 3 4 5 8 7

T DI

dA

l I

cc.

Pm

cent

May

6

60 c

c.

10%

N

&l

55.7

0.91

A

pr.

15

60

“ 5y

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55.8

0.7t

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ay

4 60

“

3%

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“ 5

60

“ 1%

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4.20

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Apr

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0.25

%

HC

l 63

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25

60

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41.5

0.8f

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28

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062%

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7 .( i( t( i( -

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f .2! %

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I.24

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1.2:

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ands

T

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1.94

9.5

1.75

5.5

m.- eq.

m.4

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14.t

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cc.

$8.1

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214 Mixed and Parotid Gland Saliva

In the parotid saliva Cl concentration did not show such marked and regular dependence on the rate of secretion as in the saliva of the mixed glands. The acid-combining power diminished with the diminution of the secretion. The potassium concentration practically depended on it but the calcium concentration remained constant. If the volume of the secretion and the concentration of ions in the saliva activated by NaCl and HCl respectively are compared, it may be seen that for the mixed glands the different solutions of NaCl are equal or even somewhat stronger stimuli than different solutions of HCl. On the other hand, for the paro- tid gland only the strongest concentrations of NaCl (10 per cent) and HCl (0.25 per cent) used gave comparable secretions. The volume of the secretion, and the concentration of organic material and of different ions rapidly decreased with the diminished con- centration of NaCl, and underwent only very small changes when weaker concentrations of HCl were employed. Thus each gland responds with a specific reaction to different stimuli.

DISCUSSION

The principal fact established in this investigation is that the rate of the secretion is not the sole factor which determines the inorganic composition of parotid and mixed gland saliva. To a certain degree the ionic concentration of saliva is influenced by the nature of the stimulus acting on the receptive surface of the mouth cavity. Since the greater part of the inorganic constituents of saliva is derived by the secretory cells from the blood, the experi- ments reported above indicate that the permeability of the gland, though practically always the same for water, varies for the differ- ent ions according to the type of stimulus applied to the receptive surface. This fact may be interpreted in two different ways.

It may be supposed that when various stimuli act on the mucous membrane of the mouth cavity, they are transmitted by a special nervous process to the salivary center and may activate in the efferent neurones impulses of qualitatively different types. The secretory cells will thus receive certain nervous impulses which will make them permeable for water and for a definite combina- tion of ions in each case, depending on the stimulus used. Al- though this theory cannot be entirely excluded (Babkin, 1913; Hitsker, 1914; Mansfeld, Hecht, and Kovacs, 1929-30, 1931),

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H. Baxter 215

another interpretation seems more probable (Babkin, 1931). It may be supposed that each stimulus acts reflexly on a definite com- bination of the various parts of the salivary center which regulate the work of different sets of the secretory epithelia composing the salivary glands. Certain facts support the latter theory. Thus the inorganic composition of dog saliva differs markedly in the case of the different salivary glands, showing that the various kinds of epithelia from which these glands are formed possess different de- grees of permeability for the ions in the blood. There may be slight variations in the inorganic composition of the saliva in different dogs in response to one and the same stimulus. These varia- tions might possibly be due to some individual differences in the structure of the glands or in the metabolism or in the composition of the blood in different dogs. Although in their histological structure the parotid gland and pancreas have many features in common, the inorganic contents of their secretions are quite different (de Beer and Wilson, 1932; Ball, 1930; Johnston and Ball, 1930). The changes in the inorganic composition of the saliva in response to stimuli of different strengths depend not only on the rate of the secretion but also on the specific properties of the stimulus (cf. Table IV). This indicates that different processes are activated in each case.

Histological observations show that, in the interlobular ducts (Speichelriihren) of the salivary glands, are epithelia which secrete chiefly water (Mislawsky and Smirnow, 1896). According to Boggino (1931) iron, mercury, and bismuth salts are excreted chiefly by the epithelium of the “secretory-excretory” ducts of these glands. Therefore, it may be supposed that various stimuli, acting on the mucous membrane of the mouth cavity, activate reflexly certain, particular glandular elements of the salivary glands, or all of such elements but in various degrees. Each of these sets of epithelia has its own specific degree of permeability for the inorganic constituents of the blood.

One other point should be mentioned in connection with the reflex secretion of saliva and its inorganic composition. In these experiments (see Table I), as well as in the previous investigation already referred to above (Baxter, 1932), the particular nature of the pilocarpine secretion was revealed. The chlorine, calcium, and potassium concentrations were much lower in the pilocarpine

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216 Mixed and Parotid Gland Saliva

parotid saliva than in the saliva secreted at the same rate on meat extract or a meal of bread and meat powder. A particularly low figure was obtained for potassium (25.0 mg. per cent in “pilo- carpine” saliva against 63.9 mg. per cent in “meat extract” saliva). The acid-combining power was somewhat higher in the former than in the latter. This shows that pilocarpine must be considered as a special, artificial stimulus which provokes a particular activity of the salivary glands differing from that activated by normal re- flex action.

SUMMARY

1. A study was made of the inorganic composition of saliva obtained from the parotid and mixed glands by reflex stimulation and subcutaneous injection of pilocarpine in dogs with permanent salivary fistula.

2. The concentration of chlorine and calcium and the acid-com- bining power are considerably lower in the saliva of the mixed glands than in the parotid saliva. No great difference could be observed in the potassium concentration of either saliva, but the concentration of phosphorus was somewhat higher in the saliva of the mixed glands.

3. Different stimuli acting on the receptive surface of the mouth cavity may produce from either the parotid or the mixed glands a flow of saliva of equal volume but of different inorganic composi- tion. Under some stimuli these variations are very small, under others quite marked.

4. By diminishing the strength of solutions of NaCl and HCI introduced into the mouth, the volume of the secretion is also di- minished. The reaction of the mixed glands to NaCl is stronger than to HCl; the reverse is the case in the parotid gland.

5. When the strength of the stimulus was diminished, the con- centration of chlorine and the acid-combining power fell. No changes or only very slight ones were noted in the concentration of calcium and potassium ions under these conditions.

6. The chlorine, calcium, and potassium concentrations were much lower in the parotid saliva activated by pilocarpine than in the parotid saliva secreted at the same rate on meat extract or bread and meat powder, while the acid-combining power was equal in the two salivas, or somewhat higher in the saliva activated by pilocarpine.

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H. Baxter 217

I wish to thank Professor B. P. Babkin for his helpful criticism and advice in directing this investigation.

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Hamilton BaxterDOG

BY REFLEX STIMULATION IN THE PAROTID GLAND SALIVA ACTIVATED

CONSTITUENTS OF MIXED AND VARIATIONS IN THE INORGANIC

1933, 102:203-217.J. Biol. Chem. 

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