RENAL TUBULAR ACIDOSIS

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Effects

of Sodium

Phosphate

and Sulfate

on Renal

Acidification

in Two

Patients

with

Renal

Tubular

Acidosis

R. Curtis Morris, M.D., Carolyn F. Pie!, M.D., and Evelyn Audioun, B.S.

1)epartments of Pediatrics and Medicine, University of California School of Medicine, San Francisco, California.

(Submitted January 20; accepted for publication June 25, 1965.) This work was aided by U.S. Public Health Service Grant AM 07308-01.

ADDRESS FOR REPRINTS: (C.F.P.) Department of Pediatrics, University of California School of Medi-cine, San Francisco, California 94122.

PEDIATRICS, Vol. 36, No. 6, December 1965

RENAL

TUBULAR

ACIDOSIS

899

I

N p1tie11ts vith renal tul)ular aciclosis,

tile rate of ulinary excretion of acid,

both as titnatable acid and ammoniurn, is

abnormally low and tile urinary pH

ab-nornially high. The excretion of titratabie

acid increases to a normal rate after

infu-sion of sufficient neutral sodium phosphate

solution to produce a phosphate diuresis.4_5

This effect of sodium phosphate is generally

considered to be that of a buffer,

I

since

a pK’ of 6.8 makes sodium phosphate an

i(leal urine buffer, and the increase of

un-nary titnatable acid in affected adults occurs

vith minimal reduction in urinary pH.31

Froni these considerations the concept has

arisen that in renal tubular acidosis tile

mechanisms of cellular generation and the

cell-lulnen transport of hydrogen ion are

competent, s.; and the capacity of the cell

to achieve high lumen-paratubular

hydro-CIl iOn gradients, incompetent. Yet, in

four of six infants with renal tubular

acido-sis, Latner and Bunnard denionstnated not

only a marked increase in tile rate of

excre-tion of titratal)le acid after infusion of

neutral phosphate solution but a decrease

ill urinary pH of more than 1 unit. This

decrease in tile pH of the urine cannot be

exl)iained t5 1 1)uffer effect of 1)hOs1)hate.

Indeed, a buffer effect would militate

against further reduction in urinary 1)H, as

would a limitation of attainable

lumen-paratubular hydrogen in gradient. A

mccli-anism WiliCh could explain the fail in

un-nary pH is suggested by studies which show

that, in renal tubules stimulated to reabsorl)

sodium avidly, increased concentrations of

non-reabsorbable anions such as phosphate

and sulfate increase the excretion of

by-drogen ion.81#{176} Since sodium sulfate is a

salt of a strong acid, its effect on renal

acidification is uncomplicated by buffer

effect.

To test whether a non-reabsorbable-anion

effect could account for the

phosphate-in-duced fall in the pH of the urine in patients

with renal tubular acidosis, the renal

acidi-fication and electrolyte response to infusion

of neutral sodium phosphate and sodium

sulfate were measured in an adult (see

Case Report appended

)

and a child with

renal tubular acidosis

(

C.M.G.

)

, elsewhere

II

MATERIALS AND METHODS

Two patients with renal tubular acidosis

were studied: C.M.G., a 6-year-old girl, and

C.V., a 55-year-old woman.

Five separate studies were done when the

patients were in acidotic states, three on

Patient C.M.G.

(

Studies 1, 2, and 3), and

two n Patient C.V.

(

Studies 4 and 5).All

studies were begun in the morning after an

overnight fast. In Studies 1, 2, and 4, either

0.15 M NaSO.i* or 0.15 M Na2HPO4/

21

(pH 7.4

)f

was infused

intra-venously. The patient lay quietly in bed and

received only water as desired; urine was

collected under mineral oil via an

indwell-ing catheter, 1I)(1 emptying of the bladder

0 ‘I’o lx- referred to hereafter as sulfate solution.

I To be referred to hereafter as phosphate

(2)

was facilitated by manual compression of

the suprapubic area. Glomerular filtration

rate was measured by inulin clearance

be-fore and during infusion of the phosphate

and sulfate solutions.

In Study 1, phosphate solution was

in-fused intravenously at 1.75 mi/mm. for a

total of 180 minutes. In Study 2, sulfate

solution was infused initially as a 25-mI

“prime” given during a 5-minute period and

thereafter at a rate of 1.2 ml/min for 234

minutes. In Study 4, sulfate solution was

infused intravenously as a 30-ml “prime”

given over a 6-minute period and thereafter

at 2 mI/mm. for 67 minutes. The infusion

was stopped after 67 minutes because the

patient began to yawn and feel drowsy.

Ten minutes later the patient vomited and

for the next 6 hours had recurrent waves of

nausea. After discontinuance of the sulfate

and inulin infusion, endogenous creatinine

clearance was measured.

At the termination of each of the infusion

studies the systemic acidosis was greater

than at the beginning of the study. Studies

3 and 5 were designed to assess the effect

on renal acidification of this greater degree

of acidosis. In Study 3, voided urine was

collected under mineral oil at approximately

hourly intervals in acid-washed bottles for

the final 10 hours of a 24-hour fast. In Study

5 ammonium chloride, 4.0 gm, was given by

mouth at 9:00 A.M., and voided urine was

collected under mineral oil for the

subse-quent 30 hours at 2-hour intervals except

for a 12-hour interval extending from 7:00

P.M. to 7:00 A.M.

Volume, pH, titratable acid and

ammo-nium were measured in each urine sample

immediately after collection; sodium,

po-tassium, phosphorus, and creatinine levels

were measured later. Arterial pH and

venous levels of phosphorus and carbon

dioxide were measured as indicated in

Tables I and II.

The first two studies on the child were

separated by an interval of 6 months.

Be-fore each study she received a normal diet

supplemented by a solution of sodium and

potassium citrate calculated to provide 7.5

mEq of each daily. Through an error in

dis-pensing, she received approximately

one-fifth the prescribed strength of solution and

was therefore acidotic on admission to the

hospital for both of these studies. Study 3

was done 3 days after Study 2; during this

period alkali therapy was withheld.

In all urinary and serum samples, sodium

and potassium levels were measured with a

Baird flame photometer with an internal

lithium standard, and chloride with a

Cot-love-Aminico automatic titrator;

phospho-rus by the method of Taussky and Shorr,12

sulfate by the method of Letonoff and

Rein-hold,13 inulin by the resorcinol method of

Schreiner,14 urinary ammonium by the

microdiffusion method of Conway,15 and

titratable acid by the method of Henderson

and Palmer.16 All biochemical analyses were

done in duplicate and were discarded and

repeated if agreement was not satisfactory.

Urinary pH was measured in Studies 1, 2,

and 3 with a Beckman model G pH meter,

and in Studies 4 and 5 anaerobically at

37#{176}Cwith an Astrup pH meter. Arterial

pH was determined by the Astrup

micro-technique.17 Plasma carbon dioxide was

measured with a Van Siyke apparatus.18

RESULTS

Data obtained from the three studies

performed on Patient C.M.G. are

summa-rized in Table I. Urinary pH decreased

pro-gressively during diuresis of ether phosphate

or sulfate. During diuresis of phosphate

(

Study 1

)

the pH decreased to 6.35 from

a preinfusion range of 6.90 to 7.04. During

diuresis of sulfate

(

Study 2

)

urine pH

de-creased to a low of 6.10 from a control

range of 6.65 to 6.69. Venous CO2 content

fell in both studies, from 15.0 to 13.0 mEq/l

after the infusion of phosphate solution and

from 17.0 to 11.1 mEq/l after the infusion

of sulfate solution. In the fasting study

(

Study 3) the pH of the urine showed no

trend and never fell below 6.72 although a

fall in venous CO2 content from 18.3 to 10.1

mEq/l presumably reflected a degree of

acidosis comparable to that at the

(3)

Study 1

0-37 1.95 16.0 25.7 9.0

37-88 I.I 0.I 5.0 3.3 7.0

88-94 1.91 21. 0.0 Q.9 6.4

0.66 . . 7.04 . 7.Q7 13.0 110 4.53

1.3 6.92 6.96 ..

1.4 6.77 6.90 I3. ..

94-57 57-374 1.11 1.08 33.0 63.5 19.0 30.0 3.9 I.8 I.4 50.4 5.Q 7.0 8.80 10.3 6.79 6.33 11.0 10.2 . . 7.3 ..

13.0 103 6 .0

Study 0-48 4896 96-139 139-169 169-II 1-881 8I-336 336-373 373-403 0.94 0.94 0.70 0.60 6.8 90.0 43.’ 26.4 S9. 30.0 .6 19.6 59.0 31.0 40.3 .. 11.6 10.0 7.8 8. 7.6 . . 6.1

..

7.1 6.9 5.1 4.9 .5.1 5.2 4.1 4.0 6.69 6.67 6.69 6.63 . . 18.4 13.1

. . 17.0 III 6.3

.. ..

..

Priming dose: 0.13 M Na,SO, 5 ml. over 3-mm period Infusion: 0.15 M Na,SO at 1. mi/mm

0.67 8.03 1.09 1.08 1.16 9.9 37.3 80.0 97.4 109.09 87.2 49.4 37.6 65.6 74.1 33.1 23.3 I.0 13.0 14.0 10. 15.5 10.0 10.8 11.6 15.4 01.8 70.3 76.5 83.0 3.7 8.3 10.2 10.1 10.7 4.8 7.3 9.5 8.9 9.6 6.36 6.40 6.20 6.19 6.10 18.0 18.7 13.6 13.4 . . . . . . 11.1 103 107 .. .. 6. .. 6.6 Study S after overnight (1 4-br) fast 0-90 90-130 130-190 190-230 50.-310 310-400 400-500 500-605 0.33 0.75 I. 1.38 1.13 0.78 0.85 0.79 34.0 0.0 19.9 15.8 15.8 3.0 34.0 14.5 18.4 3.0 88.1 33.4 24.9 0.4 13.0 14.4 QQ.0 .3 7.0 21.8 26.3 Q1.3 6.7 7.1 8.3 7.1 10.3 7.9 9.5 11.0 . . ..

.

. . . . . . . . . 2.6 3.9 5.7 3.9 5.8 4.3 5.0 4.4 3.7 4.3 7.0 6.3 6.4 3.7 5.9 6. 7.08 6.87 6.97 7.07 6.79 6.7 6.84 6.88 . . . . . . . . . . . . 18.3 ii. 10.1 . . . . . . .. .. .. .. .. .. .. .. TABLE I

EFFECF OF PHOSPHATE AND SULFATE DIuR.sIs ON ACID AND ELEC’rROLY-FK EXCRETION IN

A 6-YEAR-OLD CHILD WITH RENAL TUBULAR ACID0SIs

Infusion: Isotonic Na,11P04/NaIl,P04 (p11 7.4). 0.15 M at 1.73 mi/mm

TA =titratabie acidity; Ci,, =inulin dearance.

901

Data obtained from the two studies

per-formed on Patient CV. (Studies 4 and 5)

are summarized in Table II. During diuresis

of sulfate and after the patient vomited, the

pH of the urine decreased in the final three

collection periods from a previous low of

6.82 to successive values of 6.73, 6.02, and

5.62. During this period the rate of urinary

excretion of potassium and ammonium, if

anything, increased slightly.

During the final two collection periods

of Study 4 the urinary flow and

concentra-tion and the rate of excretion of sodium and

chloride decreased appreciably, as did the

excretion rate of sulfate. The urinary

con-centration of sulfate, however, reached the

highest level during this time. Because the

mean creatinine clearance of the final three

collections was 41 mI/mm and the mean

creatinine clearance of the preceding six

collection periods was 44 mI/mm, a

meas-ured reduction in glomerular filtration rate

(

GFR

)

could not be related to the decrease

in urinary pH or reduction in the urinary

excretion of sodium.

At the time of maximal reduction of the

urinary pH, and 1 hour before its initial

(4)

Urine FIo’r (nil! nun) .60 .78 .63 Na (uEq/ mm) 163.8 I6 .8

1u .0

144.5

K

(pEq/ mm)

65.I 3.1 30.8 53.2 Cl (jsEq/ mm) 172.0 168.0 115.0 146.0 P (jumoles mm) 18.2 17.2 10.6 14.8 Time (mm) Study 4 0-30 30-47 47-82 82-98 98-122 122-151 151-169 168-210 210-400 S (jsmoles mm) 9.9 8.8 7.9 15.6 TA (juEq/ mm) 8.4 9.9 6.7 8.5 NH4 (pEq/ mm) 28.6 29.3 22.0 25.0 PH 6.86 6.90 6.87 6.91 C,5 (ml! mm,) 47.0 41.2 3l..5

43.S

Cc? (ml! mimu) 49.0 45.6 16.2 49.8 Art. P’1 7.34 Serum

(P02 Cl P

(J4Eq/ (Eq/ (my!

1) 1) /00 mimi)

17.9 117.0 2.45

Priming dose: 0.15 M NasSO4, 30 ml, over 6-mm period Infusion: 0.13 M Na,S04 at 2 mI/mm

2.21

2.04

2.21

0.889

1.15 179.0 177.1 192.0 68.2 64.0 56.7 130.0 43.3 108.0 69.6 109.0 58.8 35.2 73.4 42.2 13.6 11.8 13.1 6.2 7.0 44.0 47.5 67.5 33.3 38.8 8.2 9.3 9.5 7.2 10.3 23.8 22.0 27.0 39.2 31.8 6.84 7.00 6.73 6.02 5.62 39.6 34.6 42.6 43.3 40.8 48.1

31.4 44.1

7.30 7.30 7.30 13.4 13.8 13.0 115.0 113.0 114.0 2.12 1.94 1.46 StudyS 0-120

40 ml of NH4C1, 10%

1.04 39.0 46.6 51.9 11.1 . .

solution given by mouth

6.70 . . 40.4 .. 16.1

6.9 20.0 . . 2.5

120-240 1.50 61.5 68.2 98.! 14.4 . . 8.2 22.0 6.64 . . 47.0 . . .

.

. . ..

240-360 2.12 92.0 92.2 146.0 18.6 ..

9.5 25.0 6.80

. . 54.3 7.30 13.6 111.0 ..

360-480 1.99 79.0 84.1 115.0 20.6 . . 8.1 24.6 6.85 . . 55.8 . . . . . . ..

480-600 2.40 80.0 86.4 115.0 24.5 . . 10.7 28.1 6.82 . . 49.2 . . 13.0 . . ..

600-1320 1.75 47.5 68.2 72.0 17.7 . . 12.9 24.1 6.50 . . 45.1 .

.

. . . . ..

1320-1440 1.04 38.6 53.2 62.5 13.7 . . 8.5 20.3 6.48 . . 36.8 . . . . . . ..

1440-1560 1.28 42.6 64.9 72.0 15.2 . . 9.2 24.5 6.60 . . 41.5 . . 13.5 110.5 2.76

1560-1680 1.69 52.4 77.4 92.5 15.6 . . 9.1 25.3 6.73 . . 48.0 . . .

.

. . ..

1680-1800 2.83 75.7 95.6 119.0 18.1 . . 9.3 27.2 6.90 . . 47.6 .. 15.4 108.0 2.52 902

TABLE II

EFFEC’r OF SULFATE Diuuzsis AND ACIDOSIS ON Acm AND ELECFROLYTE EXCRETION

IN A 59-YEAR-OLD FEMALE WITH RENAL TUBULAR ACIDosIM

TA =titratabie acidity; C1,,=inulin clearance.

and venous CO2 concentrations were 13.6

and 13.4, respectively.

In Study 5 administration of ammonium

chloride was followed by venous

CO2

con-centrations of 13.0, 13.6, and 13.5 mEq/l

over a 20-hour period in which urinary pH

decreased to minimal values of 6.50 and

6.48. Thus a prolonged degree of acidosis

presumably comparable to that which

oc-curred in Study 4 was attended by a lesser

reduction in urinary pH.

COMMENT

The results obtained in these studies

in-dicate that the fall in urinary pH in our

patients with renal tubular acidosis after

infusion of neutral sodium phosphate or

sodium sulfate cannot be related solely to

an increased degree of acidosis. Our results

and those reported by others suggest that

the fall in urinary pH is due at least in part

to a non-reabsorbable-anion effect.

In dogs or humans stimulated to conserve

Na+ avidly, either by dietary restriction of

0 or induction of lowered glomerular

filtration rate,#{176}infusions of Na salts of

non-reabsorbable anions, i.e., PO4, SO4, PAH,

result in marked increases in titratable acid,

kaliuresis, and marked reduction of urinary

pH.8#{176} This effect is reversed by infusion

with isotonic NaCl.’#{176} Bank and Schwartz

postulated that because of the poor

pene-trance

(

non-reabsorbable nature

)

of PO4

and SO4, these anions persist in the renal

tubule to a greater degree than Cl

follow-ing Na+ reabsorption; an increased

electro-negativity of the lumen results, and as a

consequence of electrostatic attraction, H+

and K+ move into the renal tubular lumen

(5)

evi(leflce in the rat that C1 may be actively

reabsorbed by the distal renal tubule,19 the

exact role of the relative diffusibilities of

SO.u, PO4 and Cl is as yet unclear. By

whatever mechanism, increased lumen

dcc-tro-negativitv would favor movement of

cellular H-i-- into the tubular lumen, and

increased lumen electro-negativity has been

nleasurecl in tile distal tubule of the rat1m

and the tubule of the necturus2#{176} following

rel)lacenlent of the lunlmal fluid by a

NaSO.1 solutioll.

Low concentratioll of Cl in the lumen of

the distal tui)ule of the rat ippers to be a

critical factor in the induction of increased

lumen electro-negativitv with non-diffusil)le

afliOII.19 Iii Our I)ltients a decreased Cl

collcentratiOn ill the distal segment of the

nephron after infusion of either phosphate

or sulfate solution an I)e illferred, Sillce

both the concentration iiid rate of excretion

of urinary C1 dililinished to low values

folloving infusion of either of these salts.

Nlarked reductions in urinary excretion of

Cl following infusion of a Ileutral

phos-Phate solution were also recorded by Latner

and Burnard in their study of infants with

renal tubular acidosis. The inferred

dimin-ished concentration of Cl in the distal

seg-ment of tile renal tubule is consistent with

the postulate of increased lumen

electro-negativity following iIlfIIsiOIl of

non-reab-sorbable anion. Moreover, the apparent frill

ill the Cl concentration in the distal

seg-ment of tile renal tubule would seem to

frankly support the postulate, since an

in-creased lumen electro-negativity would

favor movement of C1 out of tile tubular

lumen just as it would favor movement of

cellular 11+ into the lumen.

Iii view of the Na + -reabsorption

re-quirement for operation of the

non-neab-sorbable-anion effect, tile known

impair-ment of Na+ conservation in patients with

renal tubular acidosis might seem to rule

out such an effect. The impairment,

how-ever, is relative. Patients with renal tubular

acidosis can achieve Na+ balance on

mod-crate Na+ restriction.21 It is of note that

after Patient CV. vomited in Study 4 the

concentration and rate of urinary excretion

of Na+ and Cl decreased substantially.

At the same time the highest concentration

of SO4 was reached in tile urille and

pre-sumably in the lumen of the more distal

part of the nephron. During this time of

presumed greatest increase of lumen

dcc-tno-negativity, the urinary pH decreased to

its greatest extent.

SUMMARY

In two patients with the biochemical

features of renal tubular acidosis, urine pH

decreased appreciably following infusion

of either a Ileutral (pH 7.4) 0.15 NI solution

of NaHPO4/NaWPO4 or 0.15 M NaSO4.

The fall in urine pH is interpreted as

re-Sultillg from the non-reabsorbable nature of

P04= and SO4. That the fall in urine pH is

mediated by an increased lumen negativity

is supported by the fact that concomitant

with tile decrease in unille pH, the urine

concentration and rate of excretion of Cl

decreased sigmficantly.

CASE REPORT OF PATIENT C. V.

A 58-year-old widow was admitted to the

Uni-versitv of California Hospital for investigation of

recurrent kidney stones which had become

symp-tomatic ten years earlier and had led to two

cystoscopic manipulations and a uretero-lithotomy.

Two and one-half years before admission she noted

gradually increasing weakness of the legs followed

one year later by progressively increasing “bone

pain,” especially of her lower legs and ribs. Seven

months before admission kidney infection was diagnosed although episodes of chills, fever, and

low back pain had occurred at approximately

yearly intervals during the preceding eight years. Neither the patient’s parents nor eleven siblings had histories of kidney stones or renal disease of

any kind. The temperature was 37.4, the respira-tions 14, the pulse 80. Blood pressure was 110/60. The patient was pleasant, slightly deaf, and ob-viously enfeebled. Muscle mass was reduced and

her bones were exquisitely tender to the slightest

pressure. CBC was unremarkable. Urinary pH

ranged from 6.8 to 7.2. Urinary culture grew E.

coli 100 million colonies/cc. Serum creatinine was

1.1 mg/100 cc. The sodium was 141 mEq, the

potassium 1.9 mEq, chloride 117.5 mEq. The CO2

content was 17.6 mEq/l. The serum calcium was

8.4 mg and phosphorus 2.7 mg/100 cc. Urinary

alpha-amino nitrogen was 41.5 mg/24 hours. An

(6)

nephro-calcinosis without evidence of obstructive uropathy.

X-ray of the bones revealed osteomalacia and

pseudo-fractures. Following potassium replacement

and continuous treatment with sodium bicarbonate

60 mEq daily, the patient noted disappearance of

bone pain and was objectively stronger.

REFERENCES

1. Albright, F., Burnett, C. H., Parson, W.,

Reifenstein, E. C., and Roos, A. :

Osteo-malacia and late rickets. The various

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1965;36;899

Pediatrics

R. Curtis Morris, Carolyn F. Piel and Evelyn Audioun

Acidification in Two Patients with Renal Tubular Acidosis

RENAL TUBULAR ACIDOSIS: Effects of Sodium Phosphate and Sulfate on Renal

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1965;36;899

Pediatrics

R. Curtis Morris, Carolyn F. Piel and Evelyn Audioun

Acidification in Two Patients with Renal Tubular Acidosis

RENAL TUBULAR ACIDOSIS: Effects of Sodium Phosphate and Sulfate on Renal

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