PRIOR to the observations of FOLIN (3) and FOLIN and DENIS (5),

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1 THE EFFECT OF ORAL ADMINISTRATION OF CREATININE ON BLOOD AND URINE. By J. D. S. CAMERON. From the Department of Physiology, University, Edinburgh. (With twelve figures and two tables in the text.) PRIOR to the observations of FOLIN (3) and FOLIN and DENIS (5), the creatinine of the blood and the urine was believed to be derived mainly from ingested protein. HALLIBURTON (6) stated that "most of the creatinine of the urine is derived from the creatine contained in the meat of the food. There is, however, a small amount of creatinine in the urine, even during starvation, which appears to represent a small percentage of creatine from the muscles." VAN NOORDEN (23) quotes VOIT (24) as stating that ingestion of meat causes a rise in the excretion of creatinine. FOLIN (3) in 1905, however, suggested the term "endogenous metabolism" to cover the "total normal tissue metabolism," and regarded it as the sole origin of creatinine. FOLIN and DENIS (5) later suggested that creatinine was " an index or measure of this total tissue metabolism. " Since these observations were made, the endogenous origin of creatinine has been universally accepted. MATHEWS (12) remarks that "a fundamental and significant fact concerning the excretion of creatine and creatinine is that the amount of these excreted in the urine per day is independent of the amount of protein taken in the food and is wonderfully constant for each individual." HALLIBURTON and M'DOWALL (7), in contrast with a previous view noted above, follow FOLIN in accepting it as endogenous in origin; while BENEDICT and OSTERBERG (1), though differing from FOLIN in his conception of the biological independence of creatine and creatinine, agreed as to the endogenous origin of the latter. SHAFFER (20, 21) disagrees with this conception of the origin of creatinine. Basing his view upon the non-increase in creatinine excretion in exophthalmic goitre, he regards this excretion not as a measure of endogenous metabolism, but as "an index of some special process of normal metabolism taking place largely, if not wholly, in the muscles." He agrees with FOLIN, and HOOGENHUYZE and VER- PLOEGH (10), as to the constancy of creatinine excretion "not only day by day but hour by hour," and as to its independence of the amount both of food protein and of muscular activity. He (19) states that there is a difference of only 0 05 grm. in excretion between low protein non-meat diet and meat diet.

2 352 Cameron The constancy of creatinine excretion has also beeii con]mented upon by numerous other observers, including SHAFFER and REINOSO (22), MYERS and FINE (14), KLERCKER (11.), and CLOSSON (2). The amount excreted per day varies with each individual, and different figures are quoted, ranging from 0 4 grm. to 1P5 grni. (VOIT (24). MAUNK (1 5), NEUTBAUER (1,I), HOFFMIAN (8)). SCOPE OF PRESENT STUDY. The series of experiments lhere reported were undertaken with a view to ascertaining the effect of the ingestion of pure creatinine upon blood and urinary creatinine concentrations. Prior to this, however, the truth of the statements quoted above was verified by a series of brief experiments designed to ascertain (1) the normal blood creatinine concentration over periods with normal protein diet and non-meat protein diet, other proteins also being as far as possible eliminated; (2) normal urinary concentrations and daily excretions over the same periods. Thereafter the effect of the oral administration of 1, 3, 5, and 7 grm. of creatinine was studied. In all of these studies the methods adopted for the estimation of creatinine concentrations were those given by FOLIN (4) employing creatinine zinc chloride for the standard solution. NORMAL BLOOD CREATININE CONCENTRATIONS. The range of normal variations in blood creatinine concentrations is shown in fig. 1. The blood concentration was ascertained at 5 to 7 M grm % 2* t t A t t t t t April tay June FIG. 1. Normal blood creatinine. To 7th May, ordinary diet. To 10th Juine, protein-free diet. days' intervals during four weeks of inormal diet with average protein intake 95 grm. daily, and six weeks during which protein intake was as far as possible nil with meat protein absolutely excluded. On ordinary diet it will be observed that the blood concentration varied between

3 Effect of Creatinine Administration on Blood and Urine mg. per cent. and 1-55 mg. per cent.; while during the period of protein-free diet the values lay between 1P15 mg. per cent. and 1P55 mg. per cent. Ordinary diet. Non-protein diet. April mg. per cent. May mg. per cent. 23 1*48,,,,,, ,,,,,, May ,,,, June 1 1P During both of these periods the subject engaged in his ordinary occupation. It would thus appear that the intake of protein has little or no influence on the blood creatinine concentration. INFLUENCE OF DIET UPON URINARY CREATININE CONTENT. The urinary excretion was observed during the above two dietetic periods. Over the period of normal diet the concentrations and daily outputs remained fairly constant. Over a typical 7-day period (fig. 2) grms O/o 0 * a. 0.1s _Jdi viv I i" Q U u Q V U U U 0 U Q 0 u u V u ol 0 Ll0uuu t)u C U U Ll u c. UUU0uUU 0-0S O O o OO O J O O 0 00 co N n c e LM(CU \N N3 Wc N ONCM Days. Total output per day.-b grm. grm. grni. grm. grm. grm. grm. FiG. 2.-Urine creatinine normal diet. 7 consecutive days. a. Creatinine concentration. b. Total output. the average daily excretion was grin., varying from to grm. The maximum figure here quoted was easily the highest obtained during the study, no other exceeding It was obtained on a Sunday and no cause can be given to account for it. VOL. XXIII

4 354 Cameron Over a typical period of non-protein diet the average daily excretion was grm. and showed extremes of grm. and grm. The concentrations over this period were also much less regular than when full protein diet was permitted (fig. 3). grms% uuq,qqq uu uq Ouuu 0 LO '.' _ N I- 4 0s2 X c LO co LO u LO 0 I- 0 co c LO 0 co co co co o 0 C* N Lb ~~3 1 2 ~ ~ Days. Total output per day.-b grn. gri. grm. grin. grm. grm. FIG. 3.-Urine creatinine non-protein diet. 6 consecutive days in middle of period of non-protein diet. a. Creatinine concentration. b. Total output. It would thus appear that meat protein intake can influence the excretion of creatinine. The difference observed here (0.3 grm.) is much greater than the difference of 0-05 grm. quoted by SHAFFER (19). As MATHEWS (12) states, however, when there is continued consumption of much protein in the diet, "increase of urinary creatinine is not seriously inconsistent with the general rule that creatinine output and protein intake are unrelated." EFFECT OF INGESTION OF CRREATININE. Following the above preliminary study, the effect of oral ingestion of creatinine upon its amount in blood and urine was investigated. During this period full diet was taken with average daily intake of protein 95 grm. The blood and urinary contents, apart from the administration of creatinine, were thus consistent with those obtained during the first of the preliminary experiments. NEuBAUER (17) in 1914 suggested the use of creatinine as a substance for use in renal efficiency testing. MAJOR (13) later employed it, while REHBERG (18) in 1926 reported upon the effect of the oral administra-

5 Effect of Creatinine Administration on Blood and Urine tion of 5 grm. of creatinine. The present study was instituted in 1927 and, following application to normal and pathological subjects, was concluded in A preliminary communication was made in Since then a further communication by HOLTEN and REHBERG (9), in which a much similar method has been employed as a renal efficiency test, has prompted the publication of the results obtained as of probable value in parallel with the results reported by these writers. During the study, 1, 3, 5, and 7 grm. of creatinine were taken successively at intervals of 5 to 6 days. The blood and urinary creatinine contents were estimated prior to the ingestion of the creatinine, following which blood was withdrawn for estimation at intervals of 1, 14, 2, 3, 4 and subsequent hours. Urine was voided at corresponding times. 1 Gram Creatinine. With the administration of this amount the maximum concentration in the blood was obtained 14 hours after ingestion, the blood creatinine concentration rising to 3-25 mg. per 100 c.c. It had returned to a normal level (1.5 mg. per cent.) in 6 hours. The urinary examinations showed the highest concentrations to be reached during the second hour after administration, this concentration being three times that of the urine prior to the commencement of the experiment. Thereafter the concentrations gradually fell, but did not return to normal levels until the following day. MgrmsY% t0 am. a.m. noon. pm. p.m. PM. p.m. om. FIG. 4.-Blood creatinine curve. 1 grm. at 10 a.m. The total amounts eliminated showed the maximum excretion to occur during the third hour, during which 0-20 grm. was excreted. Allowing for the average excretion during the trial period on similar diet (1-48 grm.), the whole gram administered had been recovered from the urine within 13 hours. The effects upon blood and urine are recorded in figs. 4 and 5.

6 356 Cameron grms *5 grin I f-' - I u 3 v S~~ u) O O ~~ )0u)N 0.5 N N\V)N N Cr) NX O a. 0I 10 II 12 I am. a.m. noon p.m. p.m p.m pmp.pm. pm pm p.m. pm. p.m p.m. FiG. 5. Urine creatinine. 1 grm. at 10 a.m. a. Urinary concentration of creatinine. b. Urinary content of creatinine. II Morn 3 Grams Creatinine. Blood.-The maximum concentration, 4-6 mg. per 100 c.c., was obtained 1- hours after administration. An approximately normal figure (1-54 mg. per cent.) was obtained 7 hours after ingestion (fig. 6). Urine.-The maximum urinary concentration was obtained 3 hours after administration and was over four times that oi the normal. The urinary concentration fell to normal levels during the night (fig. 7, a). The maximum output occurred during the third hour after administration. The total amount administered had not been recovered 10 hours after administration, but by the following morning (20 hours after) all had been accounted for (fig. 7, b).

7 Mgrms% 50, 4.5 4* *5 I*0 grms. 0o I noon p.m p.m p.m. pm p.m. p.m p.m.._,_ I. FIa. 6.-Blood creatinine curve. 3 grm. at 12 noon. I 0_ grms7, 0I2 b L 0* 0* o Go -g PwoUrn b If C{ *_-w. noon P. M. FIG. 7.-Urine creatinine. 3 grm. at 12 noon. a. Urinary creatinine concentration. b. Urinary creatinine content. O Morn.

8 358 Cameron 5 Gram8 Creatinine. Blood.-The maximum concentration of 6-43 mg. per 100 c.c. was obtained 1j and 2 hours after ingestion. The concentration 1i hours after was not ascertained and presumably might have shown a figure higher than these two. The fall in concentration took place gradually, 4 hours after administration the figure being 4-7 mg. per cent., while at the end of 6 hours the reading was 3-1 mg. per cent. No further estimations were made until the following morning, when the concentration was found to have returned to normal limits (1.54 mg. per cent.) (fig. 8). Mgrms j% 7*O S I a.m. noon. p.m. p.m. pm. Pm. Pm. am. FIG. 8.-Blood creatinine curve. 5 grm. at 11 a.m. The above figures have to be compared with those obtained by REHBERG (18), following the ingestion of a similar amount. The comparison can be best appreciated in tabular form:

9 Effect of Creatinine Administration on Blood and Urine 359 P.B.R. J.D.S.C. Creatinine Creatinine Time. in mg. per Time. in mg. per 100 c.c. plasma. 100 c.c. plasma. Before ingestion... Before ingestion minutes after. 8:40 i hour after hour 29 minutes after ,,,, ,, 20,,,, hours after ,, ,,,, 6*43 4,, 17,,,, j,,,, ,,,, 5-6 5,, 58 3,70,, 47, 6,,,3*1 23,,,1-54 It will thus be seen that the same amount of creatinine resulted in maximum concentrations of 8-8 mg. per cent. and 6-43 mg. per cent. respectively in the two subjects. These maxima were, however, obtained in both approximately 1 hours after ingestion and thereafter the return to lower levels followed practically parallel courses. Urine.-The maximum urinary concentration was obtained during the third hour following ingestion, the concentration reached being approximately six times that normally obtained. The normal concentration was barely restored during the night (fig. 9, a). The maximum output also occurred during the third hour, grm. being recovered over that period. The total administered had not been recovered from the day urine, but a night output of creatinine double that normally present resulted in the recovery of the full amount by the following morning (fig. 9, b). 7 Grams Creatinine. Blood.-With this amount the maximum concentration was attained 2 hours after ingestion, the figure reached being 9-6 mg. per 100 c.c. The fall occurred slowly and its time of return to normal was not ascertained. Five hours after ingestion the concentration was 7-2 mg. per cent., while 9 hours after, 5 mg. per 100 c.c. were still present. No further estimations were made after that time (fig. 10). In view of the high concentrations reached, and the fact that the concentration was above 5 mg. per 100 c.c. for 8j hours, it is of interest to note the entire absence of symptoms throughout the experiments. Between the times for obtaining specimens the ordinary occupation was pursued, and no restrictions were necessary even following ingestion of the largest amount. Urine.-The maximum urinary concentration was attained during

10 360 Cameron grams l I l _ 06 l l 0*5 03 b. 9rams do 0-2 l L_ I '7 06 In (4. CF) U~) 0 m 0*5 0 4 o a a.m. a.m. noon p.m. p.m. p.m. p.m. p.m. p.m. p.m. p.m. p.m. p.m. p.m. FIG. 9.-Urine creatinine. 5 grm. at 11 a.m. a. Urinary creatinine concentration. b. Urinary creatinine content. l- Morn.

11 Effect of Creatinine Administration on Blood and Urine 361 the second hour after administration of creatinine, and reached 1*665 grm. per cent., more than eight times the concentration present during the hour preceding ingestion. This normal concentration was not restored until the following day (fig. 11, a). Mgrms % l a m. noon p.m. p.m. p.m. p.m. p.m. FIG. 10.-Blood creatinine curve. 7 grm. at 11 a.m. The second hour after ingestion also gave the maximum output, grm. being excreted over this period. The full 7 grm. administered were recovered within 24 hours (fig. 11, b).

12 362 Cameron grins. grams ~~~~~~~~- 7-, i n * It ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 08 0' n I (f0 0'5 u 0 0 u,, con+to C1t ( c NO - U U 0-4 o-3 a a. 0*1 01 lo ll Morn. am noon p. m. FiG. 11.-Urine creatinine. 7 grm. at 11 a.m. a. Urinary creatinine concentration. b. Urinary creatinine content. ADMINISTRATION OF 1 GRMI. CREATININE TO OTHER SUBJECTS. With a view to ascertaining the response of other subjects to the ingestion of creatinine, 1 grm. was administered to a number of patients under treatment in the Royal Infirmary, Edinburgh,' for conditions 1 I have to acknowledge my indebtedness to Dr EDWIN MATTHEW for permission to carry out these observations.

13 Effect of Creatinine Administration on Blood and Urine 36)3 which were associated with no disturbance of creatinine metabolism. This part of the study revealed a fairly considerable degree of variation from subject to subject as shown in fig. 12. Mgrms % f I 0 i i i I i I 2 a I I I I 0 I Ily2 3 4 HOURS. FIG. 12. Curves of inormiial patients following ingestion of 1 grmn. of creatinine. 131aCk shlos rainge of conieenitrationis in 8 normnal subjects. \Wluite in(licates m11eani of these 8. I 5 ---I In all except one subject, the riaximtumi coincentration in the blood was reached 1 1 hours after ingestion, but this maximuim varied from 22 mg. per 100 c.c. to more thani 4 1 mig. per 100 c.c. In this latter concentratioin Ino estimation was Iiiade at 1 lhours, but as the concentration was 4-1 mug. per 100 c.c. at 1 hour and 2 hlouirs it is )robable that it was greater at the 1 -hour interval. The return to normal also showned variationi, but in all cases a period of more than 5 hours elapsed before return to normality. In one case this return was very markedly delayed.

14 364 Cameron The urines in this series of cases showed little departure from the original findings. In all instances the full amount ingested was recovered by the evening, within 12 hours of administration. One case showed an abnormally rapid elimination with complete recovery within 9 hours. APPLICATION TO SUBJECTS OF ABNORMAL CREATININE METABOLISM. In view of the above findings it was suggested that an indication of renal inefficiency might be obtained from the administration of creatinine to suspected cases. In these cases, however, the blood-curve was dependent upon the initial blood concentrations, while the urinary excretion was found to be delayed in all cases where the "fasting" blood creatinine content was increased. The cases thus investigated showed "fasting" concentrations varying between 2-5 and 7-4 mg. per 100 c.c., and in none did the information accruing justify continuance of the investigation. DISCUSSION. The preliminary studies bear out the observations of previous investigators. Blood creatinine concentration varies from time to time in the same subject. In the subject investigated 1 55 mg. per cent. was the highest value observed, and the normal creatinine level of 1 to 2 mg. per cent. would thus appear ample to cover all normal individuals. In the other subjects observed, no result outside this range was obtained. Diet has no effect upon it, the concentration being similar during protein ingestion and protein abstention. Ingestion of creatinine or renal inefficiency with impaired ability to excrete it lead to rise in blood content. The daily excretion in the urine remains remarkedly constant. A greater difference was obtained between protein diet and non-protein diet than reported by SHAFFER and other writers, but this difference was not sufficient to contradict the general observation of constancy of excretion. As the protein diet consisted mainly of meat protein, it is possible that the difference in excretion was due to creatinine ingestion in the meat. The ingestion of pure creatinine was followed by rise in blood creatinine concentration. In amounts up to 5 grm. the maximum concentration was obtained in 1 1 hours, with 7 grm. within 2 hours. The absorption throughout would appear to be slower than in the similar experiment carried out by REHBERG. This observer obtained a maximum concentration in 1 hours, but the concentration 1 hour earlier was little short of the maximum figure. In the present series the maximum was more slowly approached. Excretion into the urine occurred comparatively rapidly with

15 Effect of Creatinine Administration on Blood and Urine 365 resultant quick return of blood concentration to lower levels. In all instances the full amount ingested was recovered within 24 hours. The absence of symptoms throughout the experiments calls for comment. It has been suggested by some writers that increase in blood creatinine content is the cause of uraemia. This statement was certainly not borne out here. A maximum content of 9-6 mg. per 100 c.c. was obtained, and a content of greater than 5 mg. per cent. was present for more than 8 hours following the ingestion of 7 grm. During that period ordinary occupation was followed and no gastro-intestinal or nervous symptoms were experienced. The blood-pressure also remained normal throughout. It would therefore appear that a raised blood creatinine content alone does not account for the symptoms of uraemia. The application of the experiment to other subjects was directed towards the possible employment of creatinine as a substance for utilisation in renal efficiency testing. It showed, however, that even in normal individuals the response to the ingestion of 1 grm. varied within comparatively wide limits. When applied to subjects with a fasting blood creatinine concentration above normal levels it was found that no information was obtained which could not be secured from the fasting estimation alone. It was thus concluded that as a means of diagnosing renal inefficiency creatinine administration was of no value. This is in opposition to the views of MAJOR, and of HOLTEN and REH- BERG, who regard creatinine as a suitable substance for use in such testing. In the former's test 0 5 grm. is administered intravenously, while HOLTEN and REHBERG give 3 grm. orally. The tests are thus not strictly comparable with that recorded above. SUMMARY. 1. The constancy of blood and urinary creatinine amounts is verified during periods of (a) protein and (b) non-protein diet. 2. The effect of ingestion of 1, 3, 5, and 7 grm. of creatinine upon blood and urine contents is recorded. 3. Administration of 1 grm. creatinine to a series of normal individuals shows that wide variations of response are obtained. 4. Similar administration to subjects of renal impairment gives no information which cannot be obtained from estimation of "fasting" blood creatinine concentration. 5. These findings suggest the unsuitability of creatinine administration as a test for renal function. 6. It is concluded that raised blood creatinine concentration alone does not cause "ursemic" symptoms. This work was carried on with the aid of a grant from the Earl of Moray Fund of the University of Edinburgh.

16 366 Effect of Creatinine Administration on Blood and Urine REFERENCES. (1) BENEDICT, S. R., and E. OSTERBERG, Journ. Biol. Chem., 1914, xviii (2) CLOSSON, 0. E., Amer. Journ. Physiol., 1906, xvi (3) FOLIN, O., ibid., 1905, xiii (4) FOLIN, O., " A Laboratory Manual of Biological Chemistry," New York, (5) FOLIN, O., and W. DENIS, Journ. Biol. Chem., 1914, xvii (6) HALLIBURTON, W. D., " Biochemistry of Nerve and Muscle," London, (7) HALLIBURTON, W. D., and R. J. S. M'DowALL, " Handbook of Physiology," 19th ed., London, (8) HOFFMAN, Virchows Arch. f. path. Anat., 1869, xlviii (9) HOLTEN, C., and P. B. REHBERG, Acta Med. Scand., 1931, lxxiv (10) HOOGENHUYZE, C. J. C. VAN, and H. VERPLOEGH, Zeit. f. physiol. Chem., 1905, xlvi (11) KLERCKER, K. 0. af, Bioch. Zeit., 1907, iii. 45. (12) MATHEWS, A. P., " Physiological Chemistry," New York, (13) MAJOR, R. H., Journ. Amer. Med. Assoc., 1923, lxxx (14) MYERS, V. C., and M. S. FINE, Journ. Biol. Chem., 1913, xiv. 18. (15) MuNK, H., Deutsch. Klin., 1862, No. 30, 299. (16) NEUBAUER, C., Ann. d. Chem. u. Pharm., 1862, cxx. 27. (17) NEUBAUER, C., Munch. med. Woch., 1914, lxi (18) REHBERG, P. B., Bioch. Journ., 1926, xx. 447, 461. (19) SHAFFER, P. A., Amer. Journ. Physiol., 1908, xxii (20) SHAFFER, P. A., ibid., 1908, xxiii. 1. (21) SHAFFER, P. A., Journ. Biol. Chem., 1914, xviii (22) SHAFFER, P. A., and E. A. REINOSO, ibid., 1910, vii. 30. (23) VAN NOORDEN, C., " Metabolism and Practical Medicine," London, (24) VOIT, C., Zeit. f. Biol., 1868, iv. 77.