"ESSENTIAL" AND"NONESSENTIAL" AMINO ACIDS IN THEURINE OF SEVERELYBURNEDPATIENTS1

By GEORGEL. NARDI

(From the Department of Surgery of the Harvard Medical School at the Massachusetts GeneralHospital, Boston, Mass.)

(Submitted for publication June 11, 1953; accepted February 10, 1954)

The negative nitrogen balance of thermal traumais a well recognized phenomenon (1, 2). Themeaning and significance of this to body metabo-lism are poorly understood. Partition of urinarynitrogen may assist in interpreting the significanceof nitrogen loss. Walker (3) and Taylor, Leven-son, Davidson, and Adams (4) found an increasein nonprotein urinary nitrogen of burned patients.This was chiefly due to undetermined nitrogen, thelatter defined as the difference between the totalnonprotein nitrogen and the sum of urea, uric acid,creatinine, and alpha-amino nitrogen. To analyzethis partition further we have studied the urinaryamino acid excretion of severely burned patients.Amino-aciduria has been found after severe thermaltrauma. A similar amino-aciduria has been ob-served after comparable surgical trauma, suggest-ing that the phenomenon is nonspecific. Similarstudies on patients with hypercorticism (Cush-ing's disease) suggest that the adrenal gland maybe operative in the amino-aciduria of thermaltrauma.

MATERIALS AND METHODS

The paper chromatographic technic described by Mar-tin and Synge (5), Consden, Gordon, and Martin (6),and Dent (7) was utilized to study the urinary excre-tion of free amino acids. Hydrolysis of urine was notcarried out, and so the role of peptiduria cannot beevaluated.

Aliquots of 24-hour urine collections were analyzed fornitrogen (Kjeldahl) and volumes corresponding to 250micrograms of total nitrogen were chromatographedtwo-dimensionally. The first solvent consisted of phenoland water; and the second, of butanol, propionic acid, andwater (8). The papers were developed by sprayinglightly with 0.1 per cent ninhydrin in ethanol.

Using this technic, urine of normal people is found tocontain mainly glycine and alanine with occasional tracesof other "nonessential" amino acids. In general, onlythe lower molecular weight, "nonessential" amino acidsare found in urine (9-11).

1These studies were aided by financial support fromDepartments of the Army and Navy, NR114-198.

Five members of our laboratory personnel served as"normals." Figure 1 represents the amino acid pat-tern of the person in this group showing the greatest ex-cretion of amino acids. It also illustrates our chart-ing conventions. The amino acids have been arbitrarilyclassified as "essential" and "nonessential" in terms ofthe latest available information regarding the necessityof their presence in the diet of normal adult human be-ings in order to maintain positive nitrogen balance (12).Within both groups the amino acids have been arrangedin order of increasing molecular weight.

The severely burnedSix severely burned patients were studied. All were

brought to the hospital shortly after injury except CaseNo. 52-51, who was transferred from another hospital48 hours after injury. All had suffered extensive thermaltrauma involving from 15 to 65 per cent of the total bodysurface.

All patients were in good general health prior to beingburned. Treatment was similar in each instance. Plasmaand blood were used for colloid replacement according toa standard formula (13). Penicillin and streptomycinwere administered in every case. All the burned areaswere treated with occlusive dressings. Administrationand calculation of oral intake were supervised by aspecial dietitian. Twenty-four hour urine samples werecollected in bottles containing thymol and toluol by meansof an indwelling catheter. Aliquots were used foranalyses.

The unburnedSimilar observations were done on patients undergoing

conventional surgical procedures. In order of increasingmagnitude these procedures were: excision of fissure inano, hemorrhoidectomy, herniorrhaphy, total hysterec-tomy, and subtotal gastrectomy. All operations wereelective and all patients in good general and nutritionalcondition. Gas-oxygen-ether anesthesia was used in allbut the first two cases, where spinal anesthesia was uti-lized. Postoperatively, saline, glucose, and water wereadministered intravenously until the patient's oral intakewas adequate.

In an attempt to evaluate the role of the adrenal glands,three patients with hypercorticism due to fullblown Cush-ing's disease were studied. Twenty-four hour urine col-lections were carried out before and after radical subtotaladrenalectomy. A minimum of fourteen days was per-mitted to elapse after surgery so that any effects due to

847

GEORGEL. NARDI

NORMAL MWEAKNORMAL USTRONGESSENTIAL AMINO MOLEC SACIDS WEIGHTL &2 4THREONINE 105VALINE II7LEUCINE 131I OLEUCINE 131LYSINE 146METHIONINE 149

I.PHENYLALANINE 165_TRYPTOPHAN 204

TOTAL I

NON-ESSENTIALAMINOACIDSGLYCINE 75ALANINE 89SERINE 105PROUNE 115HYDROXYPROLINE 131ASPARTIC ACID 133HISTIDINE 155ARGININE 174TYROSINE 181GWTAMI ACID 183CYSTINE 240

TOTAL 2 2 4 2 3

UNKNOWNSTAURINE

= GWTAM_N_

TOTAL 2 3424

FIGURE 1

surgical trauma per se (as seen in the previous group)might be minimized.

RESULTS

The burned

The findings in the burned patients are reportedin order of increasing severity. There are twocharts for some patients. The first represents theamino acid excretion patterned after Figure 1;the second corresponding chart, suffixed by theletter A, shows the simultaneous over-all nitrogenbalance and gross amino-aciduria for the same pa-tient. Since volumes of urine containing equalamounts of nitrogen were chromatographed daily,the significance of the "A" chart becomes obvious.If the amino-aciduria represents a constant per-centage of the nitrogen excretion, then chroma-tography of urine containing equal amounts of

nitrogen should result in equal amounts of totalamino acid on the chromatogram.

A 19-month-old boy with deep second degreeburns of 17 per cent of his body surface (Figure2, Case 52-88) showed a pattern of amino acid ex-cretion only slightly greater than normal. If tau-rine and glutamine were to be excluded, the pat-tern might be considered at the upper limit of our"normals."

A similar pattern is seen in the amino acid ex-cretion of a 42-year-old man who suffered a ther-mal burn of 30 per cent of his body surface; abouthalf of this was full thickness (Figure 3, Case 52-70). Amino-aciduria subsided somewhat after thefirst four weeks.

Figure 4 (Case 52-51) demonstrates the aminoacids present in the urine of a 30-year-old linemanwho suffered deep, high voltage, electrical burnsof the entire right arm and both thighs. The armwas amputated at the shoulder and both legs wereradically debrided at the time of admission, 48

CASENO. -WEM(52-88 * STRONG

ESSENTIAL AMINO MOLEC DAYS POST BURNACIDS WEIGHTI 2 3 4 5 6< 8THREONINE 105VALINE 117LEUCINE 131I SLEUGINE 131LYSINE 146

IMETHIONINE 149PHENYLALANINE 165TRYPTOPHAN 204

TOTAL 2 1 1

NON-ESSENTIALAMINO'ACIDSGLYCINE 75

_ALANINE -ag_SERNE 105

PROUNE 115INE 131

ASPARTIC ACID 133HISTIDINE 155

INE 174iTYOSIE 181

I GLUTAMICACID 183ICYS'TINE 240

-0 ~~TOTAL = 51515 3 -UNKNOWNS __TAJRINE m____

=GLU* -__

TOTAL 8 8 8 65

FIGUiE 2

848

AMINO-ACIDURIA IN THERMALTRAUMA

CASENO. _WEAK52-70 U STRONG

ESSENTIAL AMINO MOLEC DAYSPOST MRNITHREONINE IIS III105IVALINE I_11__II _1TT7111111LEtCINE 131 __T_ lILX_XII XI II11 1111lSOL UCINE _131 __I_I ___I

ILYSINE

TOTALfNON-ESSENTIALAMINOACIDS

-GLYGINEI IALANINE= SERINE

PROUNE-HYDROYINE-ASPARTIC ACOI HISTIDINE

ARGiNiNETYROSINE

I CLUTAMICACIDYSTiNE

TOTAL

I[IAURINLIGWTAMINE

TOTAL

149165

hours after injury. His convalescence was un-

eventful. Taurine and glutamine were againpresent. The over-all amino acid excretion ap-

peared greater than normal throughout the periodof observation. In Figure 4A this patient's ni-trogen balance has been charted synchronouslywith the number of amino acids excreted. Ni-trogen balance was calculated by subtracting thegrams of nitrogen (Kjeldahl) in the urine, feces,and dressings from grams of nitrogen administeredby mouth and parenterally. It is of interest to notethe relative constancy of the amino-aciduria de-spite the shifts in nitrogen balance.

Figure 5 (Case 52-90) represents the amnino-aciduria of a 23-year-old manwho suffered thermalburns of 40 per cent of his total body surface, mostof which were full thickess. Amino-aciduria was

still present after forty days, at which time many

areas were still unhealed. After 139 d;ay4, whengrafting had been completed, reduction in amino

acid excretion, particularly as regards the "essen-tial amino acids, is envdent.

The amino acid pattern of a 45-year-old woman

with 50 per cent body surface burns, over half ofwhich were full thickness, is summarized in Fig-ure 6 (Case 52-92). She died seven days afterburning, while in oliguria. The serum nonproteinnitrogen had risen from a value of 31 mg. per centat the time of admission to 135 mg. per cent twodays before death. Figure 6A demonstrates thatthe period of amino-aciduria corresponded roughlyto the period of greatest nitrogen negativity. How-ever, amino-aciduria persisted after restoration ofpositive nitrogen balance, suggesting that the quan-

titative and qualitative excretion of amino acidswas independent of the over-all nitrogen balance.

A 64-year-old woman with a thermal burn of64 per cent of her body surface, more than halfof which was full thickness, died on her tenth hos-pital day. Amino-aciduria persisted, though sub-siding, until the time of death (Figure 7, Case52-83). In Figure 7A the amino acid excretionagain fluctuates independently of over-all nitrogenbalance. The terminal reduction of amino acid ex-

cretion may have been due to a reduced glomerularfiltration.

FIGURE -3

849

1146

T

GEORGEL. NARDI

CASENQ -WEAK AD AdS SpoCf52-51 STRONG OSrSnod

ESSENTIAL AMINO MOLEC DAYSPOSTBURNACIDS WEIGH A 010. 2 3 4 5 6 7 8THREONINE 105 I

=VALINE _ 117 1 I_131

=ISOLEUCINE 146_1_LYSINE14

METHIONINE 149_PHENYLALANINE !65

TRYPTOPHAN 204

_ ~~~TOTAL --2I 2_

NON-ESSENTIALAMINOACIDSGLYCINEALANINE 89SERINEPROLJNE 115___HYDROXYPROLINE 131ASPARTIC ACID 133HISTIDINE 155ARGININE 174

__TYROSINE 181GWTAMICACID 183CYSTINE 240

TOTAL 4 3 4 4 3 4 444 3

UNKNOWNSTAURINEGWTAMNE

TOTAL 7 4 8 88 6 75

FIGURz 4

The unburned

Chromatography of the preoperative urine speci-mens of the five patients undergoing surgery re-vealed a normal pattern in every case. Minorprocedures such as hemorrhoidectomy and ex-cision of fissure in ano resulted in little if any de-viation from normal. Partial gastrectomy (Figure8, Case S-3) resulted in somewhat less amino-aci-duria than that seen in Figure 5. Hysterectomyand herniorrhaphy resulted in a pattern which laybetween that of gastrectomy and hemorrhoidec-tomy.

The three patients with Cushing's diseaseshowed a greater than normal urinary excretionof amino acids before operation. Figure 9 illus-trates the typical findings in one of these cases.The patient was a 42-year-old womanwith a ruddyface, abnormal fat distribution, hirsutism, and hy-pertension. A two-stage, radical, subtotal, adrenal-ectomy was carried out under cyclopropane anes-thesia. The postoperative course was uneventfuland the dosage of cortisone was gradually reducedfrom 200 mg. per day to a daily maintenance doseof 30 mg. over a period of two weeks. After thismaintenance dose had been established, daily uri-nary collections were carried out for five days.Despite the possible residual effects of surgery, the

AMINO ACIDS

NITROGEN BALANCE

2 4 6 8

CASE NO. 52-51FIGURt 4A

CASENO. _ WEAK AJ1-Adinion SWc52-90 U STRONG

ESSENTLAL AMINO MOLEC DAYSPOSTBURNACIDS WEIGHTADI1 2 3 4 S 6 7 89ID~1014442194

NON-ESSENTIALIAMINO ACIDS I

mI I

FIGURE 5

o

0

o0

zw

I--z4-20

-00

(.

+

-~ AdmODAYS

LEUCINETL

850

+104

AMINO-ACIDURIA IN THERMALTRAUMA

CASENO. WEOfAKiIS9.c52-92 U STRONG OaSP.,5.of

ESSENTIAL AMINO MOLEG DAYSPOCSTACIDS WEIGHTAOI2 34 56789

e^^ ^s I, f=, 34_ l I I I I

NON-ESSENTIALAMINOACIDS

-I - ~~~I -

FIGURE 6

-WEAK AQ*Admsion Swc* STRONG

TOTAL

NONESSENTIALIAMINO ACIDSGLYCNE 75_ALANINE 89ISERINEIPROUNE

105115

PROLINE 131ACID 133

155174l8e

ACID 183II %Af%

TOTAL

TOTAL

240

FIGuR 7

2 3 4 5 7 S 9 10DAYS CASE NO. 52-83

FIGURE 7A

II

I

z

I

4 ioLL.0

0*

*40-

t30-.

z +20.

z

410ic o

*20,

AMINO ACIDS

NITROGEN BALANCE

C. _ =

GASENQ 52-92FIGUR 6A

851

LI

44 to

62 a

GEORGEL. NARDI

I~J PRE.'Pwpg Ow.e*STRO*4; omSpe;;. .puotiiESSENTIAL AMINO MOLLEC OAYSAt= WFlTmED I *3.£S. a 90

INO.ESSENTIAL*uW rAe-.nc

FIGURE 8

minimal amino acid excretion is striking. Figure9A shows the reduction of amino-aciduria in thepostoperative phase as well as the over-all nitrogenmetabolism.

CASENO. 41 *STROMESENTIAL AMIO MOLEC PREOP POST-OPACIDS WEIGHT I 2 34 5 67 2 3 4 £7

NOW-ESSENTALI amn ntire

FIGURE 9

PRE-OP POST-OP0-loZDAYS CASENO. 41

FIGURE 9A

DISCUSSION

Amino-aciduria accompanied the increased uri-nary nitrogen loss which follows severe thermaltrauma. It was also present after major surgicalprocedures. It consisted of an increase in boththe lower molecular weight, "nonessential" aminoacids normally found in urine and the higher mo-lecular weight, "essential" amino acids not usuallypresent. There was some suggestion that boththe qualitative and quantitative aspects of theamino-aciduria may be proportional to the severityof the trauma. Patients who were not burnedseverely enough to endanger their lives and pa-tients undergoing minor surgical proceduresshowed only minimal amino acid excretion with apreponderance of "nonessential" amino acids.Those dying of their burns or undergoing majorsurgery had a massive excretion of both "essential"and "nonessential" amino acids.

The actual mechanism of this amino-aciduriais not clear. There are three possibilities. Amino-aciduria may result when elevated blood aminoacid levelJ exceed the renal threshold. With nor-mal blood: levels, renal damage and failure of tu-bular reab*orption may cause amino-aciduria.Finally, s-ino-aciduria may be seen with normalblood levelsand "intact" kidneys in certain "meta-bolic" disorders-i.e., "primary amino-aciduria"as in the. 4 Toni-Fanconi syndrome and cysti-nuria. A3tougthe available data are inadequateto rule out such a m in thermal trauma, ametabolic disorder of this sort seems unlikely. Itwould seem most likely, then, that the escape ofamino acids observed is due to either elevatedplasma amino acid levels or renal dysfunction (al-

852

AMINO-ACIDURIA IN THERMALTRAUMA

though no evidence for the latter has been found),or a combination of these two mechanisms.

Elevation of alpha amino nitrogen in the bloodof eight of twelve patients with thermal burns inthe first 24 hours after injury has been demon-strated (14). However, marked hemoconcentra-tion was present in these patients. Repeatedplasma amino nitrogen levels determined in ourpatients when hemoconcentration was not presentwere always found to be within normal limits, i.e.,less than 5 mg. per cent.

Everson and Fritschel (15) failed to show anyrise in plasma amino nitrogen subsequent to anes-thesia and surgery. Friedberg and Greenberg(16) and Li, Geschwind, and Evans (17) sug-gest that cortical extract or adrenocorticotropichormone may increase the level of plasma aminoacids. Greif (18), however, found a significantfall in the plasma amino acid level of a hypopitui-tary patient receiving adrenocorticotropic hor-mone. Russell (19) found that the increase inblood urea in nephrectomized rats resulting fromintravenously administered amino acids was mark-edly reduced by this pituitary hormone.

The high protein intake administered to con-valescing burned patients might be a factor in ele-vating the plasma amino acid level. Dent andSchilling (20) showed that after ingestion of pro-teins large rises occurred in the concentration ofmany amino acids in the portal blood of dogs, whichcould be accompanied by amino-aciduria. It isdoubtful that a high protein intake played a sig-nificant role in our patients, since the amino-aci-duria was subsiding as the patients improvedclinically and were able to ingest more protein.In addition, the surgical patients received littleor no protein during the first days of convalescence.

Certainly all these factors, protein breakdown,shock, and increased steroid production, are op-erating in the burned and traumatized patients.However, it seems unlikely that increased bloodconcentration of amino acids alone can account forthe observed amino-aciduria.

After administration of ACTH to a patient,Ronzoni, Roberts, Frankel, and Ramasarma (21)found an increase in urinary amino acid excretion,which returned to normal upon cessation of ther-apy. However, Russell and Wilhelmi (22) dem-onstrated an improved rate of de-amination inadrenalectomized rats when cortisone was adminis-tered. Burnett (23) suggested that steroid ad-

ministration improved tubular reabsorption inAddison's disease. Cagan, Klein, and Loewe (24)felt that cortisone caused increased tubular reab-sorption of intravenously administered aminoacids in treated Addisonians. It is possible thatone of the adrenal steroids other than cortisone isresponsible for failure of tubular reabsorption, butwe have no evidence for this at present. Sinceadrenal hyperfunction is probably present in allour burns, cortisone may be suspected as a causa-tive factor.

The kidney may play a specific role in the amino-aciduria of trauma. Amino acids seem to re-semble glucose in their renal behavior. How-ever, the mechanism of tubular reabsorption mustdiffer since phlorizin poisoning does not produceamino-aciduria. Since amino acids filter freelythrough the glomerulus, amino-aciduria may re-sult from failure of tubular reabsorption. Pitts(25) has shown a competitive tubular reabsorp-tion for creatin and glycine. Since numerous in-vestigators (26 - 28) have shown the presence ofcreatinuria in burns, a possible explanation for anaccompanying amino-aciduria is suggested. How-ever, since such competition exists only at veryhigh plasma levels, this factor is probably of noimportance.

Finally, the influence of amino acids themselveson the renal tubules must be considered. Kaminand Handler (29) have shown that the excretionof threonine and histidine was easily effected bythe presence of an unusual quantity of any otheramino acid in the plasma. Perhaps the presence ofa disorderly, albeit not elevated, pattern of aminoacids in the renal tubule is enough to initiate a dis-turbance of tubular reabsorption.

SUMMARY

An abnormal amino-aciduria consisting of ex-cretion of "essential" amino acids not normallypresent in urine as well as increased quantities of"nonessential" amino acids was found in the urinesof severely burned or traumatized patients.

The qualitative and quantitative aspects of thisamino-aciduria may be proportional to the severityof the trauma. The amino acid excretion was in-fluenced by but not completely dependent uponthe total urinary nitrogen. Hyperactivity of theadrenal cortex as seen in Cushing's disease re-sulted in a moderate degree of amino-aciduria.The latter effect was not reproduced by a daily

853

GEORGEL. NARDI

maintenance dose of 30 mg. cortisone after bi-lateral subtotal adrenalectomy.

This escape of amino acids is most likely due toa failure of tubular reabsorption. The reason forthe latter is not clear but may be due to someadrenal steroid other than cortisone, to an ab-normal amino acid pattern presented to the tu-bule, or to some other factor.

ACKNOWLEDGMENT

The author desires to express his thanks to Dr. OliverCope for help and encouragement and to Miss Anne Poulosfor invaluable aid in making and interpreting the chro-matograms.

REFERENCES

1. Browne, J. S. L., Conference on Bone and WoundHealing, Second meeting, December 11 and 12,1942. Published by Josiah Macy Jr. Foundation,New York, N. Y.

2. Moore, F. D., Langohr, J. L., Ingebretsen, M., andCope, O., The role of exudate losses in the proteinand electrolyte imbalance of burned patients. Ann.Surg., 1950, 132, 1.

3. Walker, J., Jr., A study of the azotemia observed aftersevere bums. Surgery, 1946, 19, 825.

4. Taylor, F. H. L., Levenson, S. M., Davidson, C. S.,and Adams, M. A., Abnormal nitrogen metabolismin patients with thermal burns. New England J.Med., 1943, 229, 855.

5. Martin, A. J. P., and Synge, R. L. M., A new form ofchromatogram employing two liquid phases. I.A theory of chromatography. 2. Application to themicro-determination of the higher monoamino-acids in proteins. Biochem. J., 1941, 35, 1358.

6. Consden, R., Gordon, A. H., and Martin, A. J. P.,Quantitative analysis of proteins: A partitionchromatographic method using paper. Biochem.J., 1944, 38, 224.

7. Dent, C. E., A study of the behavior of some sixtyamino-acids and other ninhydrin-reacting sub-stances on phenol-'collidine' filter-paper chromato-grams, with notes as to the occurrence of some ofthem in biological fluids. Biochem, J., 1948, 43,169.

8. Calvin, M., and Benson, A. A., The path of carbonin photosynthesis. IV: The identity and sequenceof the intermediates in sucrose synthesis. Science,1949, 109, 140.

9. Dent, C. E., Applications to study of amino acid andprotein metabolism. Partition chromatography.R. T. Williams, ed., Biochem. Soc. Symposia No.3, Cambridge, Cambridge University Press, 1950,p. 34.

10. Brick, I. B., The clinical significance of amino-aci-duria. NewEngland J. Med., 1952, 247, 635.

11. Individual Metabolic Patterns and Human Disease.An Exploratory Study Utilizing PredominantlyPaper Chromatographic Methods. Publication

No. 5109, The University of Texas, Austin, Texas,1951.

12. Almquist, H. J., Nutritional Applications of the AminoAcids, Chapter X, in Amino Acids and Proteins,Greenberg, D. M., Springfield, Ill., Charles CThomas, 1951.

13. Cope, O., and Moore, F. D., The redistribution ofbody water and the fluid therapy of the burnedpatient. Ann. Surg., 1947, 126, 1010.

14. Levenson, S. M., Adams, M. A., Green, R. W., Lund,C. C., and Taylor, F. H. L., Plasma alpha aminonitrogen levels in patients with thermal burns.New England J. Med., 1946, 235, 467.

15. Everson, T. C., and Fritschel, M. J., The effect ofsurgery on the plasma levels of the individual es-sential amino acids. Surgery, 1952, 31, 226.

16. Friedberg, F., and Greenberg, D. M., Endocrine regu-lation of amino acid levels in blood and tissues.J. Biol. Chem., 1947, 168, 405.

17. Li, C. H., Geschwind, I., and Evans, H. M., The ef-fect of growth and adrenocorticotropic hormones onthe amino acid levels in the plasma. J. Biol. Chem.,1949, 177, 91.

18. Greif, R. L., in Proceedings of the First ClinicalACTH Conference, J. R. Mote, ed., Philadelphia,The Blakiston Co., 1950, p. 392.

19. Russell, J. A., The effect of purified growth hormoneon urea formation in nephrectomized rats. Endo-crinology, 1951, 49, 99.

20. Dent, C. E., and Schilling, J. A., Studies on the ab-sorption of proteins: The amino-acid pattern inportal blood. Biochem. J., 1949, 44, 318.

21. Ronzoni, E., Roberts, E., Frankel, S., and Ramasarma,G. B., Influence of administration of ACTH onurinary amino acids. Proc. Soc. Exper. Biol. &Med., 1953, 82, 496.

22. Russell, J. A., and Wilhelmi, A. E., Metabolism ofkidney tissue in the adrenalectomized rat. J. Biol.Chem., 1941, 137, 713.

23. Burnett, C. H., The action of ACTHand cortisoneon renal function in man. Trans. Second Confer-ence on Renal Function, N. Y., S. E. Bradley, ed.,Josiah Macy Jr. Foundation, 1951, pp. 106-115.

24. Cagan, R. N., Klein, R. L., and Loewe, L., The disap-pearance of infused amino acids from plasma ofhospitalized control and Addisonian subjects. J.Clin. Endocrinol. & Metab., 1953, 13, 429.

25. Pitts, R. F., A renal reabsorption mechanism in thedog common to glycine and creatine. Am. J.Physiol., 1943, 140, 156.

26. Clark, E. J., and Rossiter, R. J., Carbohydrate metabo-lism after burning. Quart. J. Exper. Physiol.,1944, 32, 279.

27. Croft, P. B., and Peters, R. A., Nitrogen loss afterthermal burns. Effects of adding protein andmethionine to diets of rats. Lancet, 1945, 1, 266.

28. Nathanson, I. T., and Wilson, H., Personal communi-cation.

29. Kamin., H., and Handler, P., Effect of infusion ofsingle amino acids upon excretion of other aminoacids. Am. J. Physiol., 1951, 164, 654.

854