Plasma Renin Activity in Relation to Serum Sodium Concentration and Body Fluid Balance H

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Plasma Renin Activity in Relation to Serum Sodium Concentration and Body Fluid Balance H. H. NEWSOME AND F. C. BARTTER Endocrinology Branch, National Heart Institute, National Institutes of Health, Bethesda, Maryland 20014

ABSTRACT. The relationship of peripheral tivity decreased (109 to 62 ng/100 ml) during plasma renin activity to changes in body fluid overhydration in spite of a decrease (140 to volume and to serum sodium concentration was 129 mEq/1) in serum sodium concentration. Downloaded from https://academic.oup.com/jcem/article/28/12/1704/2715533 by guest on 29 September 2021 studied in normal subjects and in hypertensive Expansion of intravascular volume in a patient patients during changes in hydration or changes with a defect in renal sodium conservation re- in sodium intake. There was an inverse relation- sulted in suppression of plasma renin activity. ship between renin activity and fluid volume; It thus appears that some factor related to body e.g., renin activity increased (168 to 833 ng/100 fluid balance, perhaps intravascular volume, may ml in normal subjects) following loss of body be more important than serum sodium concentra- fluid (—2.1%) by diuresis. In contrast, the tion in determining plasma renin activity. (J relationship of renin activity to serum sodium Clin Endocr 28: 1704, 1968) concentration could be reversed; e.g., renin ac-

INCE the relationship of the renin-an- sodium intake; diuretics were administered S giotensin system to the adrenal cortex during the period of lowest sodium intake. was postulated in 1958 (1) and later con- Changes in water balance. Six normal volunteers firmed (2-6), the regulation of renin se- were placed on a diet containing each day 109 cretion has received increasing attention. mEq of sodium (Na) and 500-800 ml total Several factors have been implicated in water (water content of foodstuffs and water of the control of plasma renin concentration. oxidation, combined). During the'control peri- It has been shown that plasma renin is in- ods a constant amount (1000-1500 ml) of extra water was given to each subject. Dehydration versely related to sodium intake (7) and to was effected by withdrawal of the extra water serum sodium concentration (8). It is clear for 48 to 96 hr. Overhydration was established by that other factors such as fluid balance increasing the daily water intake to 2000 to may be involved (9-11). The present study 3000 ml and by administering Pitressin tannate examines the relative roles of serum sodium in oil intramuscularly twice daily. The subjects remained throughout the study in an air-con- concentration and of body fluid volume in ditioned environment. Normal, moderate phys- the control of plasma renin activity. The ical activity was permitted. Body weight, blood results of the study suggest that changes in hemoglobin and hematocrit, blood urea nitro- body fluid volume may supersede serum gen, and serum sodium, potassium, chloride and sodium concentration as a determinant of carbon dioxide content were determined daily. Peripheral plasma renin activity was measured plasma renin activity. in the venous blood of each subject during periods of normal hydration, dehydration and Materials and Methods overhydration. Plasma renin activity was measured in 15 subjects under various conditions of water and Changes in sodium balance. The 5 normal vol- of sodium balance. Changes in water balance unteers and 4 patients with benign hyperten- were accomplished in 6 normal volunteers by sion were maintained on constant daily water overhydration and dehydration; Pitressin tan- intake and studied while each received high nate in oil was administered during the periods (240 mEq), moderate (109 mEq) and low of overhydration. Changes in sodium balance (9 mEq) amounts of dietary Na. While receiv- were accomplished in 5 normal volunteers and 4 ing 9 mEq of sodium daily, the subjects were patients with hypertension by changing the given Mercuhydrin intramuscularly (1 or 2 ml each day). All other conditions and analyses Received January 5, 1968; accepted August 7. were the same as those of the preceding group. 1704 December 1968 RENIN, SERUM SODIUM AND FLUID BALANCE 1705

TABLE 1. Effect of changes in hydration on renin activity, serum sodium and changes in body weight in six normal subjects Hydration— Norm Under Over Norm Under Over Norm Under Over Under Over Renin activity Serum sodium Changes in body weight Supine Upright mEq/1 % Change ng/100 ml B.S. 145 166 94 140 144 126 -2.14 +3.60 C.J. 145 215 64 141 140 132 -2.58 +2.90 E.J. 101 162 30 140 146 127 -1.64 +3.61 L.C. 91 134 107* 255 401 207 140 144 125 -1.95 +2.91 Downloaded from https://academic.oup.com/jcem/article/28/12/1704/2715533 by guest on 29 September 2021 L.B. 146 143 39 302 878 38 140 148 130 -2.22 +4.91 G.T. 72 450 78 267 743 151 139 147 128 •3.41 +3.61

* Overhydration not optimally achieved due to emesis.

Peripheral plasma renin activity was measured The pressor responses obtained in the rats in the venous blood of each subject during the were analyzed statistically by the method of period of high-sodium intake (240 mEq), of Bliss (13). Data analysis was facilitated by use normal sodium intake (109 mEq) and of low of a Honeywell 360 computer. A check for sodium intake (9 mEq). Renin activity was parallelism between dose-response curves of assayed during the period of low-sodium intake standard and unknown was done for each only after administration of Mercuhydrin. sample. Results, expressed in ng of angiotensin in 100 ml of plasma (ng/100 ml plasma + SEM), Albumin infusion. A study was done in a patient represent the amount of angiotensin generated (E.M.) with hypertension, arteriolonephro- from endogenous substrate by endogenous renin sclerosis, and a slightly impaired ability of the in 3 hr of incubation at 37 C. Mean recovery for kidney to conserve sodium on a low-sodium the method, when angiotensin was added to diet. Daily Na intake was 109 mEq for 8 days, plasma from nephrectomized dogs, was 31 + followed by 9 mEq for 8 days. At the end of the 13% (SD). The results presented in this paper period of 9 mEq of Na intake 75 g of human were not corrected for recovery. In an estimate serum albumin (9 mEq Na) was given intra- of precision, values from 5 aliquots of pooled venously. Plasma renin activity, serum Na plasma with a mean potency of 1111 ng/100 ml concentration and urinary Na were measured showed a standard deviation of 34 ng/100 ml. immediately before and after albumin infusion No pressor activity was detected in the plasma and several times thereafter. Body weight was from 3 nephrectomized patients awaiting renal recorded daily. transplants. No pressor activity was detectable when epinephrine (100 /xg/100 ml), norepine- Measurement of plasma renin activity. Blood phrine (100 jug/100 ml), or Pitressin (10 mU/ samples were drawn with the subjects either in 100 ml) had been added to the plasma. the supine position at 8 AM and/or in the upright position at 12 noon. The subjects were Results kept supine for 8 hr or remained up and about for 4 hr before blood sampling. Changes in water balance. An individual Plasma renin activity was determined by a study on changes in water balance in a nor- modification of Boucher's method (12). The mal subject is shown in Fig. 1, and all the modifications are as follows: data on six normal subjects are summarized in Table 1. During the dehydration period in 1. The material was eluted from the column E.J. (Fig. 1) serum Na concentration in- without acidification with acetic acid, and was frozen immediately in a flask immersed in a creased from 140 to 146 mEq/1, renin activ- slurry of dry ice and acetone. ity increased from 101 to 162 ng/100 ml, 2. The frozen material was lyophilized and while body weight decreased by 1.64%. washed 3 times with 80 % ethanol. With dehydration (Table 1), renin activity 3. Three aliquots of each sample were injected into at least 3 rats and compared in each rat (supine and upright) was increased in every with 3 doses of standard Val-5, angiotensin subject except L.B., at a time when serum amide (Ciba), according to a 6-point bioassay Na concentration had increased or re- design. mained the same and body weight had con- 1706 NEWSOME AND BARTTER Volume 28

HYDRATION J.C.. 0. E.J.,0. No INTAKE 07-12-87 Normal Under Over 06-66-78 April 1966 Nov. 1966 H2O 240 109 9+Hq (mEq/d) INTAKE SERUM 140, PITRESSIN Na mEq/1 135 V... 145 250 No 13 5 200 URINARY mEq/l 125 150 Downloaded from https://academic.oup.com/jcem/article/28/12/1704/2715533 by guest on 29 September 2021 Na 100 50 URINARY IOO l- Na L 0 mEq/d 0 L 63 B.W. 61 55 kg B.W. 59 53 •x/ 1500 si 1000 200 500 s RENIN 0 150 ACTIVITY RENIN 3000 100 ng% ACTIVITY U 20001- 50 1000 ng% \ 0 0 I 3 5 7 I 2 DAYS FIG. 2. Effect of changes in sodium intake on serum FIG. 1. Effect of changes in hydra tion on serum Na, urinary Na, body weight and renin activity sodium (Na), urinary sodium (Na), body weight in the supine and in the upright positions in a nor- (B.W.) and renin activity in the supine position in mal subject. Na depletion was accomplished by an a normal subject. intake of 9 mEq Na/day plus the administration of a mercurial diuretic (Hg). sistently decreased by more than 1.5%. in serum sodium concentration from 140 to During the overhydration period in E.J. 129 mEq/1 was significant at the p<.01 (Fig. 1), serum sodium concentration de- level. creased from 140 to 127 mEq/1, renin activity decreased from 101 to 30 ng/100 ml and Changes in sodium balance. In Fig. 2 is de- body weight increased by 3.6%. With over- picted an individual study on changes in hydration (Table 1), renin activity (supine sodium balance in J.C., a normal subject. and upright) was decreased in every in- In Table 2, all the data on five normal sub- stance except that of the supine state in jects and four patients with hypertension L.C. and G.T., at a time when serum Na are summarized. The subject on a daily in- concentration had decreased by at least 9 take of 109 mEq of sodium was assumed to mEq/1 and body weight had increased by be in a normal state; sodium was added to more than 2.8%. (240 mEq/day total) or sodium was re- A test of significance for paired observa- moved from (9 mEq/day with Mercuhy- tions was used. The mean increase of renin drin) the diet. During the period of high Na activity from 62 ng/100 ml in overhydra- intake in J.C. (Fig. 2), renin activity (su- tion to 143 ng/100 ml in dehydration was pine) decreased from 179 to 138 ng/100 ml, significant at the p < .05 level. The decrease serum Na concentration did not change, December 1968 RENIN, SERUM SODIUM AND FLUID BALANCE 1707

TABLE 2. Effect of changes in sodium intake on renin activity, serum sodium and changes in body weight in five normal subjects and in four patients with hypertension

Na intake 109 9+Hg 240 109 9+Hg 240 109 9+Hg 240 9+Hg 240 Renin activity Serum sodium Changes in body weight ng/100 ml mEq/1 % Change Supine Upright Normal Subjects L.L. 268 348 72 793 541 235 138 137 137 -2.28 -.15 Y.N. 121 1181 116 221 1687 338 140 135 138 -2.81 + .93 J.C. 179 1531 138 200 2442 154 139 136 139 -2.50 +2.67 Downloaded from https://academic.oup.com/jcem/article/28/12/1704/2715533 by guest on 29 September 2021 B.S. 115 612 46 146 664 150 138 136 137 -3.42 + 2.67 C.J. 156 498 114 159 647 165 137 136 138 -3.15 + .20 Hypertensive patients J.T. 135 1167 135 357 7678 135 138 135 138 -3.03 - .82 C.I. 825 5640 732 2003 12912 1337 136 137 140 -7.99 - .55 C.S. 365 2060 193 449 2348 209 140 134 139 -1.56 +2.41 R.C. 99 518 70 135 752 116 142 134 143 -1.83 + 1.56 and body weight increased by 2.67%. Dur- weight and serum sodium concentration de- ing the period of high Na intake (Table 2), crease, while renin activity rises markedly. renin activity (supine) decreased in the five These relationships are the same in normal normal subjects and in three of the four pa- subjects and in patients with hypertension. tients with hypertension; renin activity in When serum sodium concentration and the upright position decreased or remained body fluid balance change in the same di- the same in all but one subject (Y.N.). The rection with varied sodium intake, the re- serum Na concentration showed no consis- nin activity is inversely related to both se- tent change and the body weight increased rum sodium concentration and fluid bal- in six of the nine subjects. ance. During the period of sodium depletion in The relationship of renin activity to J.C. (Fig. 2), renin activity (supine) in- serum sodium concentration can be re- creased from 179 to 1531 ng/100 ml, serum versed, as is evident in the hydration study. Na decreased from 139 to 136 mEq/1 and For example, during overhydration the body weight decreased by 2.50%. With the serum sodium concentration decreased, exception of the "upright" value in L.L., body weight increased even more than it renin activity increased substantially in all did with the high Na diet, and renin activ- normal subjects and in all patients with ity was suppressed. Renin activity was hypertension. Serum Na concentration de- again inversely related to the body weight, creased slightly in all subjects except C.I., but renin activity now varied directly with and body weight consistently decreased. serum Na concentration. It appears that plasma renin activity responds in a consis- Correlations. In Fig. 3 are shown three-di- tent manner to changes in fluid balance, as mensional graphs of results from changes in indicated by body weight, regardless of dietary sodium intake and in water balance. changes in serum Na concentration. The renin activity is depicted in relation to In Fig. 4A comparison is made between serum Na concentration on the left and in renin activity in the state of Na depletion relation to changes in body weight on the and that in the state of dehydration. So- right. As dietary Na increases, both body dium depletion produced a greater increase weight and serum sodium concentration in plasma renin activity, and slightly tend to increase slightly, while renin activ- greater loss in body weight than did dehy- ity decreases. As dietary Na is restricted dration. Sodium depletion is associated and sodium diuresis is produced, body with a significantly negative sodium bal- 1708 NEWSOME AND BARTTER Volume 28

SERUM No CONCENTRATION % CHANGE IN BODY Wt. (mEq/l) 3000-

9+Hg

FIG. 3. Graphs (o = upright Downloaded from https://academic.oup.com/jcem/article/28/12/1704/2715533 by guest on 29 September 2021 position; x= supine position) in 3 dimension show the relationship of renin activity to serum Na concentration (left) and to % change in body wt (right). On the top 2 rows the relationships are shown during changes in sodium intake in normal subjects and in pa- 9+Hg tients with hypertension; on the bottom row are shown the relationships during changes in hydration in normal subjects.

5 + ance as compared to a slightly positive so- bumin was given intravenously to a patient dium balance with dehydration. A lower (E.M.) with hypertension and a defect in serum sodium concentration is seen during renal Na conservation (Fig. 5). Although sodium depletion and the urinary sodium the initial renin activity (1112 ng/100 ml reflects the intake. supine and 1151 ng/100 ml upright) on a In Fig. 4B comparison is made between 109 mEq sodium intake was elevated (there the renin activity in states of high Na in- was a negative Na balance even at normal take and that in states of overhydration. Na intake), renin activity increased on a 9 Plasma renin was suppressed to an equal mEq intake. The serum sodium concentra- degree by a high Na intake and by overhy- tion and body weight decreased concomit- dration; there was a marked increase in antly. The plasma renin activity immedi- body weight with overhydration. The se- ately prior to albumin infusion was rum sodium concentration is strikingly dif- 2264 ng/100 ml (supine); immediately after ferent in the two conditions, and the urin- the infusion it was 975 ng/100 ml (supine) ary sodium reflects the intake. and 1159 ng/100 ml (upright). This suppression of renin activity occurred despite a Albumin infusion. In order to test the ef- slight drop in serum sodium concentration fects of expansion of intravascular volume from 131 mEq/l (pre-infusion) to 129 on plasma renin activity, human serum al- mEq/l (post-infusion). December 1968 RENIN, SERUM SODIUM AND FLUID BALANCE 1709

Discussion Na DEPRIV DEHYD It is evident from our results that the N H N plasma renin activity increases or decreases J (IH8) with changes of body fluid volume during 2500 changes of both sodium and water balance. RENIN 2000 However, the inverse relationship of renin activity to serum sodium concentration ACTIVITY 1500 seen with the changes of Na intake can be ng%, 1000 Downloaded from https://academic.oup.com/jcem/article/28/12/1704/2715533 by guest on 29 September 2021 converted to a direct relationship by changing the state of hydration. Whereas an in- 500 verse relationship of serum sodium concentration to renin activity was well docu- 0 mented in the patients studied by Brown, 0 Davies, Lever and Robertson (8), and Pit- cock and Hartroft (14) have demonstrated 1.0 a correlation between serum sodium con- % LOSS centration and juxtaglomerular indices in 2.0 B W man, Meyer, Alexandre, Devaux and Mil- 3.0 liez found no such relationship of serum sodium concentration to renin activity in a 4.0 i 0.4) study of 159 hypertensive patients (5). The 100 present study suggests that renin activity CUM is not necessarily dependent upon serum so- +0 dium concentration and that some other Na BALANCE factor apparently related to body fluid bal- 100 mEq ¥ ance may be more important than serum 200 sodium concentration in determining the $027) concentration of plasma renin. As has been pointed out more recently by SERUM 150 Brown, Davies, Lever, McPherson and Na 140 Robertson (16), the conditions in which re- n nin concentration appear to relate to serum mEq /1 130 sodium concentration all tend to show char- acteristic aberrations in extracellular fluid volume (ECF). It is also interesting to note URINARY 100 that Fraser and associates (9) have demonstrated a rise in plasma renin concentration Na 50 without a change in serum sodium concen- mEq/d 0 tration after administration of furosemide FIG. 4A. Comparison of the effects of sodium depri- intravenously. In the present study a nega- vation in normal subjects (N) and in hypertensive tive fluid balance was a consistent accom- patients (H), with the effects of dehydration in paniment of increases in renin activity. The normal subjects on (mean) renin activity in the greater increases in renin activity during supine position, % loss of body weight, cumulative sodium depletion as compared to dehydra- Na balance, serum Na and urinary Na. tion suggest that the extracellular fluid compartment is the most important medi- diuretics induced an average estimated ex- ator of these volume changes. In these sub- tracellular fluid volume deficit of 740 ml in jects, the sodium loss with the mercurial the normal volunteers and 1370 ml in the 1710 NEWSOME AND BARTTER Volume 28

Na LOAD E.M., 0 06-19-02 1/17/67 Na Intake [ r mEq/d 500 I (±280) IOOL

400 ALBUMIN RENIN 75gm 300 li.V.I ACTIVITY 200 Downloaded from https://academic.oup.com/jcem/article/28/12/1704/2715533 by guest on 29 September 2021 ng% 100 0 4.0 3.0 % GAIN 2.0 B. W. 1.0 + 0 SERUM 145 Na 135 mEq/l 125 n I FIG. 5. Effect of a low sodium intake and an intra- 300 venous albumin infusion on serum sodium concen- URINARY tration and plasma renin activity in a patient with 200 an impaired ability of the kidney to conserve Na sodium. 100 mEq/d 0 stances. It is well known that the mainte- FIG. 4B. Comparison of the effects of sodium load- nance of an upright position (16,19,20) stim- ing in normal subjects and in hypertensive patients with the effects of overhydration on (mean) renin ulates renin production; this in turn has activity in supine position, % gain in body weight, been shown to result in a decrease of effec- jerum Na and urinary Na. tive plasma volume (21). A redistribution of plasma volume and a release of catecho- hypertensive patients. In contrast, the rise lamints, however, could be operative dur- of renin activity during dehydration oc- ing maintenance of the upright position. It curred in spite of an average positive so- is possible that the effect of decreases in ex- dium balance of 74 mEq. The fluid deficit tracellular fluid volume may be mediated was thus distributed over total body water, through changes in intravascular volume. and involves very small changes in extra- Meyer, Menard, Alexandre and Weil (11) cellular fluid volume. A similar relationship could prevent the rise in renin activity pertains to the control of aldosterone secre- usually seen with administration of etha- tion as a function of changes in body fluid crynic acid by infusing polyvinylpyrroli- volume (17). On the other hand, Blair-West done to expand plasma volume. In the pres- et al. (18) have pointed out the importance ent study, infusion of albumin into a pa- of serum sodium concentration, as opposed tient with moderate renal salt loss, elevated to plasma volume, in control of aldosterone plasma renin, and a low serum sodium con- secretion in sheep under certain circum- centration suppressed the plasma renin con- December 1968 RENIN, SERUM SODIUM AND FLUID BALANCE 1711 centration. Thus, hemorrhage was shown 11. Meyer, P., J. Menard, J. M. Alexandre, and B. Weil, Rev Canad Biol 25: 111, 1966. to be a stimulus to renin secretion (22) but 12. Boucher, R., R. Veyrat, J. deChamplain; and the effects of hemorrhage on renin secretion J. Genest, Canad Med Ass J 90: 194, 1964. 13. Bliss, C. I., The Statistics of Bioassay, Aca- (or circulating angiotensin) could be re- demic Press, New York, 1952. versed by expansion of intravascular vol- 14. Pitcock, J. A., and P. N. Hartroft, Amer J ume (23). Path 34: 863, 1958. 15. Meyer, P., J. M. Alexandre, C. Devaux, C. References Leroux-Robert, and P. Milliez, Presse Med 74: 1. Gross, F., Klin Wschr 36: 693, 1958. 2025, 1966. Downloaded from https://academic.oup.com/jcem/article/28/12/1704/2715533 by guest on 29 September 2021 2. Genest, J., W. Nowaczynski, E. Koiw, P. 16. Brown, J. J., D. L. Davies, A. F. Lever, Sandor, and P. Biron, In Bock, K. D., and D. McPherson, and J. I. S. Robertson, Clin P. T. Cottier (eds.), Essential Hypertension, Sci 30: 279, 1966. Springer-Verlag, Berlin, 1960, p. 126. 17. Bartter, F. C, G. W. Liddle, L. E. Duncan, 3. Laragh, J. H., M. Angers, W. G. Kelly, and J. K. Barber, and C. Delea, J Clin Invest 35: S. Lieberman, JAMA 174: 234, 1960. 1306, 1956. 4. Bartter, F. C, A. G. T. Casper, C. Delea, and 18. Blair-West, J. R., G. W. Boyd, J. P. Coglan, J. D. H. Slater, Metabolism 10: 1006, 1961. D. A. Denton, M. Wintour, and R. D. Wright, 5. Carpenter, C. C. J., J. O. Davis, C. R. Ayers, Aust J Exp Biol Med Sci 45:1,1967. and A. Casper, J Clin Invest 40: 2026, 1961. 19. Cohen, E. L., J. W. Conn, and D. R. Rovner, 6. Mulrow, P. J., and W. F. Ganong, Yale J Biol J Clin Invest 46: 418, 1967. Med 33: 386, 1961. 20. Gordon, R. D., O. Kuchel, G. W. Liddle, and 7. Brown, J. J., D. L. Davies, A. F. Lever, and D. P. Island, J Clin Invest 46: 599, 1967. J. I. S. Robertson, Lancet 2: 278, 1963. 21. Fawcett, J. K., and V. Wynn, J Clin Path 13: 8. ; Brit Med J 2: 144, 1965. 304, 1960. 9. Fraser, R., V. H. T. James, J. J. Brown, 22. Brown, J. J., D. L. Davies, A. F. Lever, P. Isaac, Q. F. Lever, and J. I. S. Robertson, J. I. S. Robertson, and A. Verniory, J Physiol • Lancet 2: 989, 1965. {London) 182: 649, 1966. 10. Brown, J. J., D. L. Davies, A. F. Lever, and 23. Hodge, R. L., R. D. Lowe, and J. R. Vane, J J. I. S. Robertson, J Endocr 32: v, 1965. Physiol {London) 185: 613, 1966.