(Received 31 December 1937)

Transcription

1 208 J. Physiol. (I938) 92, 208-2I8 6I :6I2.0I5.2 THE EFFECT OF SALT DEFICIENCY IN MAN ON THE VOLUME OF THE EXTRACELLULAR FLUIDS, AND ON THE COMPOSITION OF SWEAT, SALIVA, GASTRIC JUICE AND CEREBROSPINAL FLUID BY R. A. McCANCE From the Biochemical Laboratory, King's College Hospital, London (Received 31 December 1937) THE experimental production of salt deficiency in normal persons provided an opportunity of studying its effect upon the volume and composition of certain of the body fluids, and it was thought that it would be profitable to do so since very little information is available on the subject. Such literature as there is will be discussed in the appropriate sections of the paper. The salt deficiency was produced by diet and sweating [McCance, 1936 a, b]. The fluid intake was liberal and unrestricted. The chemical methods employed have previously been given [McCance & Widdowson, 1937a]. The changes in the serum and red blood cells have already been described [Mc Cance, 1937]. RESULTS The volume of the extracellular fluids Lavietes et al. [1936] have described methods for the determination of the volume of the extracellular fluids in man, depending upon the administration of substances which in the main do not penetrate into the cells and whose concentration may readily be measured in the plasma and urine. Sucrose was one of these substances. The method employed was to inject a known amount intravenously, and to determine the proportion of this excreted and the concentration in the plasma after stated intervals. From the amount excreted it was possible to calculate the amount left in the body at the given times and, assuming the concentration of sucrose in the other extracellular fluids to be the same as it was in the plasma, it was possible to calculate the volume of liquid in

2 SALT DEFICIENCY AND EXTRACELLULAR FLUIDS 209 which the amount left in the body was dissolved, i.e. the volume of the extracellular fluids. The volume of extracellular fluids can also be obtained from the change of concentration in the serum within any one period and the amount excreted in that period. In the present experiments sucrose was injected into one subject on four occasions for kidney function tests, and inulin was injected into two others for a similar purpose [McCance & Widdowson, 1937b]. From the behaviour of sucrose and our knowledge of the chemical and physiological properties of sucrose and inulin, it may be assumed that the distribution of inulin in the body is, like sucrose, probably confined to the extracellular fluids. McCance & Widdowson [1937b] kept no record of the exact amount of sucrose or inulin injected, but the followidg data were available: (a) a record of the amount of sucrose or inulin excreted in each of four to eight successive periods of min., (b) a record of the concentration of the sucrose or inulin in the plasma half-way through each period. Three methods therefore could be used for the determination of the volume of the body fluids in which the sucrose or inulin was dissolved (the extracellular fluids): (1) The total amount excreted in each period could be divided by the fall in plasma concentration within that period. The latter could be obtained graphically from the plasma concentrations determined in the middle of each period. This gave a series of results for any one experiment which could be inspected and averaged. (2) The total amount excreted during the whole experiment could be divided by the total fall in plasma concentration within that time. This is really a variation of the first method, but in practice does not always give the same answer as the averaged result obtained by it, because in each method a different experimental error tends to preponderate. (3) If it was assumed that the volume of fluid in which the inulin or sucrose was dissolved remained constant from the first period to the last, the amount left in the body (z) at the beginning of the first period could be calculated thus: (z - a) x 100 (z - a') x 100 b b' where a and a' are the amounts excreted between the beginning of the first period and the end of any two periods and b and b' the plasma inulin or sucrose at the end of these periods. (In practice the first and last periods were used.) Hence the amount of fluid in which the inulin or sucrose was dissolved at the end of each period could be found from the concentration in the plasma and the amount left in the body at that time. All three methods have been used. The first two do not involve the

3 210 B. A. McCANCE assumption that the volume of fluid in which the sucrose or inulin was dissolved remained constant throughout the experiment. This assumption, however, can be justified by the experience of Lavietes et at. [1936] and, so far as D.W. and J.T.B. were concerned, by the direct results of method (1). For one of the inulin subjects (R.M.L.), on whom four experiments were carried out, the first method of calculation gave results which suggested that the volume of fluid in which the inulin was dissolved increased throughout each experiment so that it was greater at the end than it had been at the beginning. This may possibly have been the case, but the same apparent result might have been obtained in the presence of a constant volume of extracellular fluid if the plasma had not been in equilibrium with the whole of it when the blood samples were withdrawn. Inulin diffuses so much more slowly than sucrose [Bunim et al. 1937] that something of this sort may have been happening in this particular subject. Alternatively the results may have been due to experimental variations inherent in method (1) and this appears equally probable since this method always tended to give erratic results from one period to the next. Owing to this uncertainty, it has been decided only to give and to discuss in detail the results obtained on subjects D.W. (sucrose) and J.T.B. (inulin), in both of whom the data by all three methods were consistent and satisfactory. It may be added, however, in passing that the results obtained on R.M.L. entirely support the conclusions to be drawn from D.W. and J.T.B. The full data for one experiment on D.W. and one on J.T.B. are given in Table I and the results of all six experiments on these two men TABLE I. Data from two experiments D.W. Second normal experiment J.T.B. Salt-deficient experiment Plasma Plasma Sucrose sucrose Inulin inulin Duration excreted in the Duration excreted in the of in each middle of of in each middle of No. of period period each period period period each period period min. g. mg./100 c.c. m4. g. mg./100 c.c * * * are given in Table II. Both subjects were of similar build and height. As might have been expected from what is known of sodium chloride metabolism the deficiency brought about a considerable reduction in the extracellular fluid volume [Harrop, 1936], and it is interesting to note

4 SALT DEFICIENCY AND EXTRACELLULAR FLUIDS 211 TABLE II. A comparison of the extracellular fluid volumes during health and during salt deficiency Volume of the extracellular fluids (litres) During salt deficiency Subject and Method of Normal _r Normal substance used calculation (before) 1 2 (after) D.W. (sucrose) * J.T.B. (inulin) * TABLE III. A comparison of the loss of body weight and of the extracellular fluid volumes brought about by salt deficiency Extracellular fluids Body weight Extracellular fluid as p.c. of body weight kg. litres r A_ A > A During Subject At start Loss At start Loss At start deficiency D.W J.T.B. 76-5* *0 4* * In a previous paper [McCance & Widdowson, 1937b] J.T.B.'s weight at one stage of his salt deficiency was erroneously given as 87 kg. increasing overnight to kg. The figures should have been 72-3 and kg. the return to the higher figure with recovery. Table III shows the extracellular fluid losses compared with the losses of body weights. In compiling this table D.W.'s preliminary findings were taken to be the normal ones and the values obtained in the two deficiency experiments were averaged and subtracted from them. These figures for the normal extracellular fluid volumes are of the same order as those obtained by Lavietes et al. [1936], but they suggest that inulin may tend to give slightly lower values than sucrose. This is being investigated. The recorded loss of body weight in these experiments is presumably the mean of (a) the loss of extracellular water, (b) possibly some loss of cellular nitrogen and water [McCance, 1936a, b], (c) a gain in cellular water due to the reduction of the plasma osmotic pressure [McCance, 1937]. Nitrogen balances were not recorded in these subjects and it is doubtful if the fluid losses have been measured with sufficient accuracy usefully to compare the expected with the actual losses of weight. It is, however, obvious that one effect of salt deficiency has been to reduce very materially the percentage of the total body weight occupied by the extracellular fluids. Knowing the change in the volume of the extracellular fluids and the change in concentration of plasma ions [McCance, 1937] brought about PH. XCII. 14

5 2.12 R. A. MoCANCE by salt deficiency, the total loss of these ions from the extracellular fluids can be calculated. Thus D.W.'s normal of extracellular fluid containing 101 m.eq. of 01/1. were reduced by salt deficiency to containing 83 m.eq./l. This represents a loss of some 41 p.c. of his extracellular chloride. Similar calculations show that J.T.B. lost 51 p.c. of his extracellular chlorides. It is thought by some at the present time that, except for the red blood cells, the chloride ion is confined to the extracellular fluids. If this is so, the data now presented would give a measure of the total body chloride and the percentage loss brought about by salt deficiency. Direct determinations of chloride, however, made on whole animals suggest either that there must be a considerable quantity of chloride outside the extracellular fluids or else that the volume of the extracellular fluids as determined by sucrose and inulin is too low [McCance, 1936a; Lavietes et al. 1935, 1936; Harrison et al. 1936]. These substances may, however, legitimately be employed (as in the present instance) to make comparative measurements of the volume of the same man's extracellular fluids at two different times. The composition of resting saliva c.c. of juice were collected in a measuring cylinder without any gustatory or mechanical stimulation and sampled without being filtered. The juice appeared to be secreted at a normal rate during salt deficiency. The chlorides were determined directly, the sodium and potassium after dry ashing and the results are shown in Table IV. It will TABLE IV. Composition of saliva Normal health mg./100 c.c. During salt deficiency mg./100 c.c. Subject r A- --,% A r Sodium Chloride Potassium Sodium Chloride Potassium J.T.B D.W R.A.M W.M.G R.M.L Average Average (as m.eq./l.) * be observed that salt deficiency consistently produced a fall in the concentration of sodium and a rise in the concentration of potassium. The changes in chloride concentration were inconsistent. There is no previous work with which to compare these findings. The normal concentrations of sodium and potassium in the present investigation are on the whole lower than those of Brown & Klotz [1937]. The difference

6 SALT DEFICIENCY AND EXTRACELLULAR FLUIDS 213 may be due to the fact that Brown's subjects stimulated their salivary secretion by chewing paraffin. The concentrations of chloride agree with those found by Welin & Frisk [1936]. Gastric juice It has been known for some time that the continuous removal of gastric juice from animals does not radically alter the composition of the juice [Dragstedt & Ellis, 1930]. Lim & Ni [1925-6] for instance found that the gastric glands of dogs continued to secrete in spite of dehydration and a loss of up to half the body chlorides. Katsch & Mellinghoff [1933] and Mellinghoff & Heuschert [1934] removed gastric juice from patients for 10 hr. a day for 3-5 days and found no consistent reduction in the volume or in the chloride secreted. The response to histamine was as good or almost as good on the last day of treatment as it had been on the first. In the present investigation fasting gastric juice was removed and then 0 5 mg. ofhistamine hydrochloride was administered subcutaneously. Gastric juice was then withdrawn (usually at 15 mi. intervals) over a period of min. The procedure was repeated when the salt deficiency was most severe. The normal and deficient fasting juice was sometimes very small in amount and it was seldom possible to make a complete analysis so the results will not be discussed. In Table V are given the The effect of salt deficiency on the composition of histamine-stimulated gastric juice Vol. collected (c.c.) Free HCl Total HCl Total Cl Total Na Total K Subject Collection time (min.) m.eq./l. m.eq./l. m.eq./l. m.eq./l. m.eq./l. Composition during normal health R.A.M. 99/ W.M.G. 53/ J.T.B. 154/ D.W. 70/ R.B.N. 192/ P.M.E. 72/ Composition during salt deficiency R.A.M. 111/ *5 W.M.G. 65/ J.T.B. 64/ D.W. 92/ R.B.N. 123/ P.M.E. 39/ TABLE V. results which were obtained from studies of the histamine juice. Filtered juice was used for the determination of free and total HCI, unfiltered juice for the determination of the other ions. Chlorides were estimated directly and the juice was dried and incinerated for the determination 14-2

7 214 R. A. McCANCE of sodium'and potassium. It will be observed that in some respects the subjects showed considerable individual variation. W.M.G. could not be made nearly so deficient as the others, and his free HCl, total HCI and chloride actually showed a small increase during his deficiency. J.T.B. on the contrary showed considerable reductions in all these constituents. It may be concluded that salt deficiency tends to reduce the concentration of acid and chloride in gastric juice but that individuals vary widely in their response. There seems to be no close relation between the changes observed in the gastric juice and those in the plasma [McCance, 1937]. Peters's [1935] review of the literature suggests that the osmotic pressure of the gastric juice should mirror accurately changes in osmotic pressure of the serum and that the concentration of chloride in gastric juice should approximately equal the concentration of base in the serum. In the present experiments the gastric juice was not withdrawn at the same time nor was it necessarily withdrawn on the same day as the blood. Further, a certain amount of saliva was swallowed, but all the same some of the findings are difficult to reconcile with Peters's generalizations. Thus the total chlorides are much too low, particularly those of J.T.B. (during deficiency) and of D.W. These low chlorides may be due to an admixture of mucus with the acid juice [Bolton & Goodhart, 1931; Welin & Frisk, 1936]. However that may be, the present experiments suggest that the mixed stomach juices may often be hypotonic. Salt deficiency appeared to bring about a fall in the concentration of sodium in the gastric juice and a rise in the concentration of potassium. It will be recalled that these changes were also noted in resting saliva. Cerebrospinal fluid Lumbar punctures were carried out on D.W. and R.M.L. at the time when they were most salt deficient. Blood was taken a few minutes beforehand, and the comparative results are shown in Table VI.' In all TABLE VI. Composition of cerebrospinal fluid during salt deficiency Sodium Chloride Serum C.s.F. C.S.F. Na Plasma C.S.F. Plasma Cl Subject m.eq./l. m.eq./l. Serum Na m.eq./l. m.eq./l. C.S.F. Cl D.W * g R.M.L * analytical procedures cerebrospinal fluid (C.S.F.) was treated in the same way as serum [McCance, 1937]. C.S.F. was not withdrawn when the subjects were in normal health, but the concentration of the sodium and

8 SALT DEFICIENCY AND EXTRACELLULAR FLUIDS 215 chloride found in these subjects' normal sera has already been published [McCance, 1937], and the normal C.S.F. chloride may be taken to be m.eq./l. (in clinical parlance mg. of NaCl/100 c.c.). The ratios of C.S.F. sodium/serum sodium (Table VI) are of the same order as those found by Dailey [1931] in patients with normal serum electrolytes, and this, taken with the known fall in serum sodium, strongly suggests that salt deficiency has brought about a fall in the C.S.F. sodium, and that the osmotic pressure of the C.S.F. has probably fallen to about the same extent as that of the serum. The chlorides in the C.S.F. have undoubtedly fallen. Clinicians will appreciate the abnormality of these salt deficient C.S.F.'s better when it is stated that the concentration of chlorides in them amounted only to 640 mg./100 c.c. (as NaCl). There is one further point of interest. Although the sodium ratios are of the order found by Dailey [1931], the chloride ratios (see Table VI) are lower in both cases. This means that the concentration of chlorides in the C.S.F. has not fallen so much as that of the chlorides in the plasma (compare with this the behaviour of chlorides in the saliva) and is quite in keeping with the modern view that the C.S.F. is a secretion rather than an ultrafiltrate [McCance, 1936b]. Sweat The sodium, potassium, chloride and nitrogen were determined in all sweats. In the earlier experiments sweat and washings were evaporated down at a faintly acid reaction and made up to a standard volume, usually 2 1. Later, the total volume of the sweat and washings was measured and samples taken for analysis without evaporation. The water lost in the sweat was assessed from the loss of body weight without correcting for the water lost in the expired air. Most subjects sweated every day for 7-10 days, but R.A.M. only sweated five times in 10 days. The routine was always the same. About 1 hr. after a light lunch the subject undressed, weighed himself and entered the previously heated radiant-heat bath. The open end was then closed with mackintosh sheeting so that only the subject's head projected, and his temperature was taken at frequent intervals and maintained as far as possible between 100 and 1010 F. by altering either the ventilation or the heating. Each subject drank the same volume of water at about the same rate each day in the hot-air bath. Some subjects took 800 c.c. and others 1000 c.c. After 2 hr. the heat was switched off and 10 min. later the subject emerged and was washed down with distilled water, dried and weighed again [McCance, 1936a, b]. Conditions therefore were comparable from day 14-3

9 216 R. A. McCANCE to day. As the salt deficiency became worse the amount of water lost remained about the same, varying to some extent with the subject (Table VII). The amount of sodium and chloride lost in the sweat invariably decreased, but more so in some subjects than others [Mc Can c e, Subject and no. of sweat Total amounts D.W TABLE VII. The effect of salt deficiency and repeated exposure to high temperatures on the composition of the sweat R.A.M R.A.M Water Sodium Potassium Chloride Nitrogen C.C. m.eq. m.eq. m.eq. mg. excreted in "standard" sweats during progressive salt deficiency * * Total amounts excreted in "standard" sweats during a period of generous salt intake D.W * * ]. Thus R.B.N. lost 2-44 g. of sodium on his first day's sweat and 1-65 on his last. J.T.B.'s daily loss of sodium declined from 4-95 to 26 g. Others fell off very much more. These results support those of Marchionini & Ottenstein [1931]-see also Glatzel [1937]. The potassium lost in the sweat remained constant in amount in some subjects and rose in others and the same may be said of the nitrogen. It follows that the sodium/potassium ratio underwent extensive alterations as the deficiency progressed. In Table VII may be found the results obtained on D.W. and R.A.M. Daly & Dill [1937], Dill et al. [1933, 1936, 1937] and Talbott [1935] have all observed somewhat similar decreases in the concentration

10 SALT DEFICIENCY AND EXTRACELLULAR FLUIDS 217 of sodium chloride in successive sweats. They consider the phenomenon, however, to be part of the mechanism of adaptation which people, who are daily subjected to high temperatures, are said to undergo. They regard it as a provision of nature to safeguard the individual from excessive salt depletion, but they do not seem to have excluded the possibility that the falling concentration of sodium chloride might be a sign of salt deficiency rather than of adaptation. In order to find out what part adaptation might be playing in the results just described, D.W. and R.A.M. subjected themselves to a second series of sweats comparable in all respects with those which they had undergone during their deprivation experiment, except that throughout the control series they took daily an abundance of salt by mouth to replace the losses in the sweat. The results are given in Table VII. It is evident that as the days passed there was no falling off in the NaCl lost in the sweat and that in fact the reverse took place. It is also of interest to note that there was an increased excretion of potassium but not to the same extent as during salt deficiency. The present results therefore show that in these subjects repeated sweating did not lead to any reduction in the excretion of NaCl unless the repeated sweating was allowed to induce a state of salt deficiency. In that event the concentration of NaCl in the sweat invariably declined and it is concluded that salt deficiency and not " adaptation " was the cause. The arrangements in the present experiment were so different from those of Ta lbo tt and Dill et al. that the results can scarcely be said to contradict their conclusions. They do however show that the decreased secretion of NaCl observed in the present experiment was due to salt deficiency and not to adaptation. SUMMARY Experimental sodium chloride deficiency in man produced: (1) A reduction in the volume of the body fluids in which injected sucrose or inulin was dissolved (the extracellular fluids). In the present experiments reductions of p.c. were observed. (2) A fall in the concentration of sodium, a rise in the concentration of potassium and no consistent change in the concentration of chloride in resting saliva. (3) A variable reduction or little change in the free and total HCl and in the total chloride of gastric juice. These changes bore no close relationship to the simultaneous chloride changes in the plasma. There was also a small fall in the sodium and rise in the potassium in gastric juice.

11 218 R. A. McCANCE (4) A fall in both sodium and chloride of cerebrospinal fluid. (5) A considerable but variable fall in the concentration of NaCl in sweat. It was shown that "adaptation" to repeated sweating did not contribute to this result. The author is very much indebted to Miss E. M. Widdowson for co-operation throughout the work, to the subjects for their willing help and to A. W. Haynes for technical assistance. Dr M. G. Eggleton very kindly read through the manuscript and made a number of valuable suggestions. Some of the expenses of this investigation were defrayed by the Medical Research Council. REFERENCES Bolton, C. & Goodhart, G. W. (1933). J. Phy8iol. 77, 287. Brown, J. B. & Klotz, N. J. (1937). J. dent. Re8. 16, 19. Bunim, J. J., Smith, W. W. & Smith, H. W. (1937). J. biol. Chem. 118, 667. Dailey, M. E. (1931). Ibid. 103, 5. Daly, C. & Dill, D. B. (1937). Amer. J. Phy8iol. 118, 285. Dill, D. B., Daly, C. A. & Bock, A. V. (1936). J. biol. Chem. 114, xxv P. Dill, D. B., Jones, B. F., Edwards, H. T. & Oberg, S. A. (1933). Ibid. 100, 755. Dill, D. B., Michelson, J. & Edwards, H. T. (1937). J. Nutrit. 13, 10 P. Dragstedt, L. R. & Ellis, J. C. (1930). Amer. J. Phy8iol. 93, 407. Glatzel, H. (1937). Ergebn. inn. Med. Kinderheilk. 53, 1. Harrison, H. E., Darrow, D. C. & Yannet, H. (1936). J. biol. Chem. 113, 515. Harrop, G. A. (1936). John8s Hopk. Hosp. Bull. 59, 11. Katsch, G. & Mellinghoff, K. (1933). Z. klin. Med. 123, 390. Lavietes, P. H., Bourdillon, J. & Klinghoffer, K. A. (1936). J. clin. Invet. 15, 261. Lavietes, P. H., D'Esopo, L. M. & Harrison, H. E. (1935). Ibid. 14, 251. Lim, R. K. S. & Ni, T. G. (1925-6). Amer. J. Phy8iol. 75, 475. McCance, R. A. (1936a). Proc. Roy. Soc. B, 119, 245. McCance, R. A. (1936b). Lancet, 1, 643, 704, 765, 823. McCance, R. A. (1937). Biochem. J. 31, McCan ce, R. A. (1938). In the Press. McCance, R. A. & Widdowson, E. M. (1937a). Lancet, 1, 247. McCance, R. A. & Widdowson, E. M. (1937b). J. Phy8iol. 91, 222. Marchionini, A. & Ottenstein, B. (1931). -Klin. W8chr. 10, 969. Mellinghoff, K. & Heuschert, C. A. (1934). Ibid. 13, Peters, J. P. (1935). Body Water, p London: Baillibre, Tindall and Cox. Talbott, J. H. (1935). Medicine, 14, 323. Welin, G. & Frisk, A. R. (1936). Acta med. 8cand. 90, 543.