The Mechanism of the Osmotic Adjustment of Body Cells As Determined in VIVO by the VOLUME of DISTRIBUTION of a LARGE WATER LOAD

The Mechanism of the Osmotic Adjustment of Body Cells as Determined IN VIVO BY THE VOLUME OF DISTRIBUTION OF A LARGE WATER LOAD

Alexander Leaf, … , Oliver Wrong, Elbert P. Tuttle Jr.

J Clin Invest. 1954;33(9):1261-1268. https://doi.org/10.1172/JCI103001.

Research Article

Find the latest version: https://jci.me/103001/pdf THE MECHANISM OF THE OSMOTIC ADJUSTMENT OF BODY CELLS AS DETERMINED IN VIVO BY THE VOLUME OF DISTRIBUTION OF A LARGE WATER LOAD' By ALEXANDER LEAF,2 JACQUES Y. CHATILLON, OLIVER WRONG, AND ELBERT P. TUTTLE, Ja.8 (From the Departments of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Mass.) (Submitted for publication April 5, 1954; accepted May 14, 1954)

Since permeability of cell membranes to water tained. A water load of 100 ml. per kilogram of body has been clearly demonstrated, there are several weight was then administered intravenously at a rate of of cells to dilution approximately 20 ml. per minute. The water load was theoretically possible responses given as a 23h per cent solution of dextrose, or dextrose of the extracellular fluid. Osmotic equilibrium and fructose. Blood samples were obtained following the might result from net movement of water into cells infusion at intervals of three to sixty minutes for five in response to extracellular dilution. On the other or six hours in three experiments. In the other experi- hand, net movement of water into cells might be ments blood samples were taken 4 to 6 hours after the infusion was completed. Some of the dogs received 0.3 averted by: 1) active transport of water out of mgm. of atropine and 50 mgm. of Dramamine® to pre- cells preventing a change in intracellular osmotic vent vomiting and salivation. activity; 2) reduction of intracellular osmotic ac- A second series of ten experiments was performed on tivity by means of either osmotic inactivation of dogs either nephrectomized or with ureters ligated. The intracellular solutes or their extrusion from the operation was done under local procaine infiltration (10 to 20 ml. of 1 per cent solution) in two animals and in cells. the remainder under general anesthesia induced and main- These possibilities were tested by determining tained throughout the experiment by the intravenous ad- the volume of distribution of a large water load ministration of 25 to 30 mgm. of sodium pentobarbital which depends on movement of water through the per kilogram of body weight. Immediately following op- body. The data are compared with the total body eration a blood sample for the natural abundance of deu- the dilution of a tracer terium was drawn, and 1 to 2 grams of deuterium oxide water content measured by per kilogram of body weight were given intravenously. amount of deuterium oxide which is independent Blood was drawn one and one-half and two hours later of net movement of water. In the dog the volume for determination of deuterium and as control samples of distribution of a large water load was found to before dilution. Dramamine® and atropine were adminis- approximate closely the total body water content. tered as above. One hundred and thirty-two ml. per kilogram of body weight of a 2.5 per cent solution of fructose and/or glucose were administered intravenously at METHODS AND PROCEDURE a rate of 30 ml. per minute. This quantity of water was chosen to increase the degree of dilution and thus to mini- A. Protocol mize the effects of the errors of measurement on the cal- Fifteen initial experiments were performed in nine un- culated results. The two final blood samples were ob- anesthetized dogs. Two and one-half to five units of tained between 23 and 3Y2 hours after the infusion was Pitressin Tannate in Oil®'4 were given two to sixteen completed. The ureteral ligatures were removed from hours before the experiment to reduce the urinary loss of four dogs, all of which recovered uneventfully. In one water. After the bladder was emptied by catheterization, of these the experiment was later repeated. the animal was weighed and a control blood sample ob- B. Analytical methods 'This study was supported in part by grants from the Plasma sodium and potassium concentrations were Milton Fund of Harvard University, the American Heart measured by flame photometry (1). Total solute concen- Association, and the Greater Boston Chapter of the tration of plasma was determined by the freezing point Massachusetts Heart Association. depression measured with a thermistor.5 Deuterium con- 2Howard R. Hughes Fellow in Medicine. centrations were measured by mass spectrometry (2). 8 Postdoctorate Fellow in Medicine, National Heart Institute, U. S. Public Health Service. 5 The apparatus was developed and constructed for us 'Kindly provided by Dr. A. C. Bratton, Jr., Parke, by Fiske Associates, Inc., 44 Bromfield Street, Boston, Davis and Company, Detroit, Michigan. Mass. 1261 1262 A. LEAF, J. Y. CHATILLON, 0. WRONG, AND E. P. TUTTLE, JR.

Urea was determined by the microdiffusion technique of TABLE I Conway (3); glucose by the method of Nelson modified The mean volume of distribution of an intravenous by Somogyi (4); fructose by the method of Rolf, Surt- water load in 15 experiments shin, and White (5); chloride by the method of Wilson and Ball (6). Plasma water was measured gravi- Mean VN,. = 65.6% of Body Weight metrically after drying at 950 to 105° C. to constant Mean Vs01 = 63.6% of Body Weight weight. Data were analyzed by conventional statistical Mean Difference = 1.9% of Body Weight methods (7). Standard Deviation = 2.3% of Body Weight (of Mean Difference) C. Calculations and analytical error to = 0.86 In the calculations of the last ten experiments the values p = 0.4 for sodium, total solutes and deuterium are the averages of repeated determinations made on two separate plasma samples obtained at short intervals, as described above. Analysis of variance reveals no significant differ- The errors of the methods were estimated by the analysis ence between the mean volumes of distribution of of variance of these repeated determinations. The co- the water load calculated from changes in concen- efficient of variation for a single determination of plasma sodium concentration was 0.95 per cent; of total solute tration of plasma sodium (VNa) and total solute concentration, 0.75 per cent; and of deuterium, 1.55 per (Vs.,), but the standard deviation for the differ- cent. As all analyses were done at least in quadruplicate ences between VN5 and Vi01 in individual experi- the estimate of the analytical error for the averages used ments was large (8.9 per cent body weight). The in the calculations was reduced to one-half or less of the results approximate the expected value for total above figures for single determinations. The volume of distribution of the water load was cal- body water in the dog. culated by the following general equation: Because of the considerable discrepancy between VNa and Vsi in individual experiments, ten (G 1) v= C2W-C2W further studies were done. To reduce errors resulting from renal losses of water and solutes, V = volume' of distribution of the water load. Cl and C2 = initial and final plasma concentrations of either the dogs were nephrectomized or their sodium or total solutes. ureters were ligated immediately prior to the W = volume of water administered. experiment. Total body water content was calculated as follows: Figure 1 shows the effects of a water load on (I VDO = 2WDO ( -F) the total solute, sodium, glucose and urea concentrations of plasma in a nephrectomized dog. VDO - deuterium space (total body water content). WD,O = weight of deuterium oxide administered. Equilibrium of distribution of the water load oc- F = atoms per cent excess of deuterium in plasma at curred within two hours. The plasma urea con- equilibrium. centration slowly increased during the study as The volumes, as calculated, had a minimum standard might be expected in a nephrectomized animal. deviation attributable to propagation of the errors of The plasma glucose concentration was still ele- measurements alone (8) estimated to be: 1.4 to 2.4 per vated above the control levels at the end of the cent of body weight for the sodium calculations, 1.6 to 3.0 experiment. per cent of body weight for total solute calculations, and approximately 0.5 per cent of body weight for the deu- The data for the last ten experiments are pre- terium space. sented in Table II. The quantity of water administered was chosen to cause a large dilution of the RESULTS body fluids with minimal toxic effects. The se- The results obtained in the initial fifteen ex- rum sodium concentrations after the water load periments performed in nine dogs are briefly sum- are in a range not uncommonly seen clinically. marized in Table I. These results were calcu- In eight experiments there occurred a slight rise lated according to Equation 1 with no attempt to in plasma urea concentration in spite of the dilu- correct the data for the small renal losses of water tion. This accumulation of urea is attributable to and solute that occurred during the experiments. the suppression of renal function. In all experi- ° No distinction has been made between liters and kilo- ments the blood glucose level was still elevated at grams of water. the time the last blood samples were drawn. This MECHANISMS OF OSMOTIC ADJUSTMENT OF BODY CELLS IN VIVO 1263

DOG SW ANESTHETIZEDANEPRETOMIZED AOWL WT. 14.79 KG.

TOTAL SOLUTE

I z 0 160-

140

120.

100

80.

60-

40- GLUC)OSE 20.

TIME IN HOURS FIG. 1. CHANGES IN TOTAL SOLUTE, SODIUM, GLUCOSE AND UREA CONCENTRATIONS IN PLASMA FOLLOWING THE INTRAVENOUS ADMINISTRATION OF A LARGE WATER LOAD TO A NEPHEECTOMIZED DOG It is evident that the plasma concentrations of sodium and total solutes had achieved constant values by 21 hours following termination of the infusion. In this experiment the plasma glucose remained elevated after the infusion (see text). was true even when fructose alone was used in the Table III shows the volume of distribution of infusing solution. The concentrations of fructose the large water load calculated from changes in in the plasma, however, never rose more than 1.3 plasma sodium (VNa) and total solute (Vs.,) con- mM per L. The persistent hyperglycemia prob- centrations, respectively. The total body water ably reflects reduced glucose tolerance resulting content before dilution, determined as the volume from the meat diet used prior to the experiment." of distribution of deuterium oxide (VD20), is also The serum potassium concentrations decreased shown. To facilitate comparison, all results are slightly in all but two experiments. In the two expressed as per cent of body weight. The plasma experiments in which serum potassium concentra- urea concentrations have been subtracted from the tion rose the changes were too small to reflect sig- total solute concentrations used to calculate V&1 nificant extrusion of intracellular potassium in in Tables III and IV to correct for the accumula- response to extracellular dilution. tion of urea during the experiments. This correction is justified because urea is known to be T Three days of glucose administration prior to the experiment in subsequent studies abolished the prolonged freely distributed over total body water. hyperglycemia noted in the present results. The results in Table III are subdivided into 1264 A. LEAF, J. Y. CHATILLON, 0. WRONG, AND E. P. TUTTLE, JR.

X two groups according to the magnitude of the rise

-4. . . '14 ~ 00- V 4 e 0 E in plasma glucose concentration (AG) that oc- 0 curred between the initial and the final blood speci- mens. Although in all experiments, Vs,1 is larger i \ c-- -- - %O than VNq, the five experiments in Group I show -44, Md \o-,-m co QN m Ch 0%C A 004' C~q an excellent agreement among VNa, and VD2O. 1! . . . . Vs.,, 4) | The discrepancies in each experiment within this group are of the magnitude expected from the analytical and sampling errors. The value of AG for 0. * . . c I'd, 00 C,0t:C!ciC this group of results is small. In Group II of o.0 0Nro-O Table III, the discrepancies between VNa and Vs., V0%40%*0%0 0%0 are considerably larger, as are the values of AG.

c"I 00 C14 and ON \000 00 0 Figure 2A shows the relationship between AG the difference between Vs., and VNa for all experiments. The correlation coefficient, 0.88, is significant. - t- @ V) V -"00--4 The accumulation of glucose or any other solute during the course of an experiment will result in a (N final concentration of total solutes which is too .0 .I b high and will minimize the expected dilution of 4, ~0 s plasma total solutes. This would cause falsely

i m .0%to ~ 00 n0 -- high values for Vs.,. If glucose accumulates in an ui 1 e 0 0e C6t el;O; V: e6 e600 f e66 ~0 -Q4, 1 osmotically active form in the extracellular fluid, 4, it not only will result in an over-estimation of V8s., 0 but also would be expected to reduce VNa. The 443 0 . .' 6 '-4 ('4 4 in the extracellular fluid 4. 31> osmotically active glucose 04 V~ e- U X~ of~ 0000 00 U.) O t C% would cause the movement of some intracellular 0 +4 00 00D 000 0\ o00 0 0 (I 0 water to the extracellular compartment. This '4 IE :i.. * . . . .V*-4 would dilute the plasma sodium in excess of the dilution produced by the water load and VNa would be underestimated. An attempt has, therefore, been made to correct the results of Table III n *4 . .. . . * . . for the measured changes in plasma glucose. In Table IV, VNa and V8s. have been corrected on the assumption that the rise in glucose concen-

tOZo6 \6 q \ o tration occurred over a volume of 30 per cent of of dif- c- body weight. This volume of distribution

* -. er 00 0o0 t 00 000 fusible glucose in the dog has recently been re- " 1; 14 V4 el 4; -4 ported by Searle, Strisower, and Chaikoff (9).

q 0000to 0In 4)U) Details of this calculation are presented in the Ap- pendix; it should be noted that the volume of dis- .,to0 00 tj -j-in \ 4~ tribution assumed for glucose does not enter into X u the correction applied to the calculation of VNa. 04m i 00 0 O 0 .3 +j The values of VD2O are again presented to facilitate comparison. The correction for plasma water

I a content and the Donnan effect, though insignifi- I- N. cant, was also applied to VNa (see Appendix). The correction for glucose abolishes the signifi- i 3 cant correlation of V8a. - VNa and AG (Figure MECHANISMS OF OSMOTIC ADJUSTMENT OF BODY CELLS IN VIVO 1265

TABLE III Uncorrected volume of distribution of administered water TABLE IV Volume of distribution of administered water corrected for (Expressed as per cent of body weight) glucose,. Donnan effect, and plasma water content (Expressed as per cent of body weight) Experiment AGt VWs. Vs1 VD20 Group I Experiment VN- V8oi VDno 1 1.09 66.7 67.5 65.6 2 4.09 60.8 64.6 60.6 1 66.2 66.0 65.6 3 0.75 58.9 66.4 65.2 2 64.1 60.5 60.6 4 2.13 64.6 70.8 64.5 3 59.6 64.8 65.2 5* 1.95 60.3 63.3 65.5 4 61.9 67.9 64.5 5 67.0 60.6 65.5 Group II 6 57.4 55.9 57.0 6 6.04 52.8 60.8 57.0 7 54.0 59.4 56.8 7 8.14 52.0 66.7 56.8 8 56.5 67.0 62.4 8* 8.78 54.8 76.8 62.4 9 63.1 71.0 66.2 9 7.17 61.5 79.7 66.2 10 62.6 71.1 65.7 10 9.05 61.7 81.5 65.7 Mean 61.2 64.4 63.0 Standard deviation of differences between means * Repeated observations on the same animal. t AG is the difference in concentration of plasma glucose V8s0 - VN. = 1.80; t = 1.76; p > .05 before and after dilution. VD2O - VN, = 0.96; t = 1.76; p > .05 VN. and Vs01 are the volumes of distribution of the water V&.1 - VD2O = 1.03; t = 1.43; p > .05 load calculated from changes in plasma sodium and total solute concentrations, respectively. VD2O is the total body water content determined from solutes. Furthermore these values closely approxi- dilution of deuterium oxide. mate the total body water content (VD2O). 2B). It is apparent from Table IV that the calculation of the volume of distribution of a large DISCUSSION water load is essentially the same whether esti- Studies with deuterium oxide have clearly dem- mated from the dilution of serum sodium or total onstrated that cell membranes are permeable to

14J

0 20 20. I", ZSj ra 0.88 rzo.55 p. 0.001 . paO.I0

0 PAt, SIl 0 I' . z . 0 .

'.. '4. 0 5 10' aG 0 AG (A) (B) CHANGES IN PLASMA GLUCOSE CONCENrRAr/oW (mOsm4 ) FIG. 2. THE CORRMATION BETWEEN CHANGES IN PLASMA GLUCOSE CONCENTRATIONS, AG, AND THE DIFFERENCES BETWEEN V8s1 MINUS ViNI (A), AND THE CORRECTED VALUES OF V8o0 MINUS Vx. (B) The correlation is significant in A, but not significant in B. 1266 A. LEAF, J. Y. CHATILLON, 0. WRONG, AND E. P. TUTTLE, JR. water. The distribution of a small quantity of the average response of the body cells to dilution. deuterium oxide throughout total body water is It is, therefore, not possible to deny that some dependent upon the movement of individual mole- cells take up more than their quota of the water cules and does not require net passage of water load whereas other cells take up less. It seems un- across cell membranes. Hence, the knowledge likely, however, that certain cells are diluted more that deuterium oxide equilibrates with total body than the average in an amount just sufficient to water yields no information about the osmotic ad- yield a volume of distribution for various water justments of the cells when a large quantity of wa- loads apparently equal to total body water. ter is introduced into the body. If enough intracellular solute were extruded The results of the present study strongly sug- from the cells, Vs.1 might equal total body water. gest that the volume of distribution of a large VNa, however, would be significantly lower unless water load is equal to the total body water con- the extruded solute were sodium. An attempt tent. Thus in vivo the osmotic adjustment of the was made to determine whether sodium was ex- great majority of body cells involves net move- truded from bones or cells. The ratio of sodium ment of water into cells so that the water load ap- to chloride in bone and most cells is much higher pears to be evenly distributed throughout total than in the extraceilular fluid. If sodium were ex- body water. truded into the extracellular fluid one might ex- This interpretation of the present findings seems pect a greater dilution of chloride than of sodium. contradictory to the conclusions of Robinson and In two instances the dilution of sodium and of McCance (10, 11), who observed that respiring chloride were identical. In the other experiments rat kidney slices maintained essentially constant the chloride dilution was highly variable and the weight in media of varying concentrations, whereas discrepancies between sodium and chloride dilu- slices whose respiration had been inhibited swelled tion correlated closely with the volume of gastric in these media. They concluded that the cells are secretions which accumulated during the experi- normally hypertonic to their environment and that ments. It seems improbable that sodium would inward diffusion of water is counteracted by an move out of bone and cells in all experiments in equal and active transport of water out of the cells. an amount just sufficient to increase VNft to the Such a mechanism would prevent net movement value of VD20 in spite of differences in the water of water into cells and the apparent volume of loads that were administered. For these reasons, distribution of a water load should then approxi- it seems unlikely that extrusion of sodium from mate only the volume of the extracellular fluid. cells or bone contributes significantly to the os- The present findings exclude the widespread oc- motic adjustment to a water load. currence of such active water transport by cells The osmotic inactivation of intracellular solutes though it is possible within the errors of measure- might be an alternative adjustment requiring no ment of this study that a single tissue or organ net movement of water into cells. This possibility might behave in the manner claimed by Robinson. must be excluded since it would result in a volume However, Mudge has shown (12) in experiments of distribution of the water load significantly less with kidney slices that shifts of electrolytes as well than total body water. as of water may occur across renal cell membranes The present results give no indication whether making Robinson's data subject to other inter- the osmotic pressure is the same or different in pretations. The findings of Opie (13) that sev- the intracellular and extracellular fluids. In either eral tissues swell in vitro in media hypertonic to case, however, the even distribution of the water normal extracellular fluid are not pertinent to the load over total body water indicates that the con- present study as they give no information of the centration ratio is the same before and after dilu- response of these tissues to dilution of their en- tion. Osmotic equality throughout the total body vironment in vivo. Furthermore this worker fails water would be the simplest explanation consistent to explain why such swelling of tissues does not with the present results. This view has been ac- occur in vivo. cepted and clearly stated by Peters (14) and is in The present study yields results representing agreement with recent cryoscopic measurements MECHANISMS OF OSMOTIC ADJUSTMENT OF BODY CELLS IN VIVO 1267 of various tissues by Conway and McCormack ni, ng = Fraction of V1 and Vs, respectively, contain- (15). ing sodium at its concentration Na1 and Na2. This study is complementary to earlier work of Concentrations in plasma of sodium, glucose Nal, Na2 and total-solutes-minus-urea before and after Hetherington (16) and Eggleton (17) and recent G1, G2 = dilution. Na and G concentrations are ex- studies of Wolf and McDowell (18). These work- SI, S2 pressed as millimoles per liter; S, in milli- ers added hypertonic saline to the extracellular osmoles per liter. fluid and measured the apparent volume of body K The factor by which Na2 is corrected for overdilution as a result of accumulation of water that diluted the administered salt. The glucose. average results of Hetherington, Wolf, and Mc- f = The factor by which plasma sodium concen- Dowell and those of Eggleton, as recalculated by tration is corrected for plasma water content Conway and McCormack (15) yielded fair ap- and the Donnan effect. proximations of total body water content. I. Correction of Vg,1 for change in glucose The total amount of solutes in m2V2 is the same as the amount in m1V1 plus the added glucose which is not metab- SUMMARY AND CONCLUSIONS olized: In twenty-five experiments, eighteen dogs were (3) m2V2gS = miViSi + (m2V2G2- mtViG) given large water loads under conditions which It is assumed that the glucose concentrations, GI and G2, minimized or eliminated renal losses. The volume are uniform throughout their respective volumes of distribution, ml and mg. of distribution of the water load was calculated The increase in concentration, AS, of total solutes re- from the changes in plasma concentrations of so- sulting from this unmetabolized glucose is: dium and total solutes. In ten experiments total body water content was simultaneously determined (4) m2V2G2A-SmVG-AS = by the dilution of deuterium oxide. Replacing m2 by its value obtained from (3): The volume of distribution of the water load as determined from the dilution of plasma solute (5) a [& - G2 ] (64.4 per cent of body weight) and sodium (61.2 Thus the general equation (1) permits calculation of Va01 per cent) concentrations was equal to total body corrected for change in glucose: water content (63.0 per cent) within the limits of (6) S- S- experimental error. The findings indicate that S2 -AS. in vivo the great majority of the body cells adjust II. Correction of VN. for change in glucose and for plasma to acute dilution of the extracellular fluid by a net water content and the Donnan factor movement of water into the cells so that the ad- The increase in osmotically active glucose in the extra- ministered water load is distributed evenly over cellular fluid may be expected to draw water from cells. total body water content. This will result in overdilution of the plasma sodium which may be corrected by a factor: ngVg ACKNOWLEDGMENTS (7) K = niV2 The authors wish to thank Miss Denise Girod and = n, and Miss Mineko Sasahara for their assistance in this study. As- equations (3) (7) may be combined to A Supply Grant from the National Institutes of Health in yield: support of a Public Health Service Postdoctorate Re- S- G search Fellowship to one of us (E. P. T.) was used in (8) K = a S2-Gg this study. Plasma sodium concentration was corrected for plasma water content and for the Donnan effect assuming one- APPENDIX fourth of the extracellular fluid to be intravascular. The Donnan factor, d, of 0.96 was accepted for a plasma pro- W = Water load in liters. tein concentration of 6 per cent and (1 - d) was consid- V1 = Volume of distribution of the water load. ered to vary directly with plasma protein concentration. V2 = VI + W. Plasma protein concentration was calculated from plasma a = Coefficient of V V water content (gm. per ml.) (19): dilution, equals V1+ Wafeafter equilibrium. (9) f 0.334 + 0.671 ml, m2 = Fraction of V1 and V2, respectively, contain- Plasma Water ing osmotically active glucose. Thus the general equation (1) permits calculation of 1268 A. LEAF, J. Y. CHATILLON, 0. WRONG, AND E. P. TUTTLE, JR.

VN, corrected for change in glucose and for plasma water 9. Searle, G. L., Strisower, E. H., and Chaikoff, I. L., content and the Donnan effect: Glucose pool and glucose space in the normal and w diabetic dog. Am. J. Physiol., 1954, 176, 190. (10) VN=f1N= 10. Robinson, J. R., Osmoregulation in surviving slices KfgNa2 from the kidneys of adult rats. Proc. Roy. Soc., Series B, 1950, 137, 378. REFERENCES 11. Robinson, J. R., and McCance, R. A., Water metabo- 1. Berry, J. W., Chappell, D. G., and Barnes, R. B., lism. Ann. Rev. Physiol., 1952, 14, 115. Improved method of flame photometry. Indust. & 12. Mudge, G. H., Electrolyte and water metabolism of Engin. Chem. (Anal. Ed.), 1946,18, 19. rabbit kidney slices: effect of metabolic inhibitors. 2. Solomon, A. K., Edelman, I. S., and Soloway, S., Am. J. Physiol., 1951, 167, 206. The use of the mass spectrometer to measure deu- 13. Opie, E. L., The movement of water in tissues re- terium in body fluids. J. Clin. Invest., 1950, 29, moved from the body and its relation to movement 1311. of water during life. J. Exper. Med., 1949, 89, 3. Hawk, P. B., Oser, B. L., and Summerson, W. H., 185. 12th ed., Practical Physiological Chemistry. Phila- 14. Peters, J. P., Water exchange. Physiol. Rev., 1944, delphia, The Blakiston Co., 1947, repr. 1951. 24, 491. 4. Somogyi, M., Notes on sugar determination. J. Biol. 15. Conway, E. J., and McCormack, J. I., The total in- Chem., 1952, 195, 19. tracellular concentration of mammalian tissues 5. Rolf, D., Surtshin, A., and White, H. L., A modified compared with that of the extracellular fluid. J. diphenylamine procedure for fructose or inulin de- Physiol., 1953, 120, 1. termination. Proc. Soc. Exper. Biol. & Med., 1949, 16. Hetherington, M., The state of water in mammalian 72, 351. tissues. J. Physiol., 1931, 73, 184. 6. Wilson, D. W., and Ball, E. G., A study of the esti- 17. Eggleton, M. G., The state of body water in the cat. mation of chloride in blood and serum. J. Biol. J. Physiol., 1951, 115, 482. Chem., 1928, 79, 221. 18. Wolf, A. V., and McDowell, M. E., Apparent and os- 7. Mather, K., Statistical Analysis in Biology, 2nd ed., motic volumes of distribution of sodium, chloride, rev. and enl. New York, Interscience Publishers, sulfate and urea. Am. J. Physiol., 1954, 176, 207. Inc., 1947. 19. Eisenman, A. J., MacKenzie, L. B., and Peters, J. P., 8. Worthing, A. G., and Geffner, J., Treatment of Ex- Protein and water of serum and cells of human perimental Data. New York, John Wiley and Sons, blood, with a note on the measurement of red blood Inc., 1943. cell volume. J. Biol. Chem., 1936, 116, 33.