URINE 529 



Creatine 



Folin-Benedict Method. 1 Principle. Creatine on boiling with 

 acid is transformed into creatinine. By determining the content of 

 creatinine before and after the acid treatment we are able to calculate 

 the amount of creatine originally present in the urine. The Folin 

 colorimetric method (page 526) is used for determining the creatinine 

 in both cases. The method is not applicable to diabetic urines. 



Procedure. Introduce into a small flask or beaker 10 c.c. of the urine to 

 be examined. (If 10 c.c. contains more than 12 or less than 7 mg. of total 

 creatinine use a correspondingly smaller or larger volume of urine.) Add from 

 10-20 c.c. of normal HC1, and a pinch or two of powdered or granulated lead. 

 Boil the mixture over a free flame as slowly or as rapidly as may be desired, until 

 very nearly down to dryness, when the heating should be continued to dryness 

 either on the water-bath or very easily by simply holding the vessel in the hand 

 and heating carefully for a moment or two. Let the residue stand on the water- 

 bath for a few minutes until most of the excess of hydrochloric acid gas has been 

 expelled, after which dissolve it in about 10 c.c. of hot water and rinse the solu- 

 tion quantitatively through a plug of cotton or glass wool (to remove all metallic 

 lead) into a 500 c.c. volumetric flask. Add 20-25 c.c. of a saturated picric acid 

 solution and about 7-8 c.c. of a 10 per cent NaOH solution, which contains 5 

 per cent of Rochelle salt. 2 At the end of five minutes fill to the mark with water 

 and read in the colorimeter just as in the case of creatinine (see page 526). 



Calculation. Calculate the creatinine content of the solution in the same 

 manner as given under Creatinine (page 527) . From the value thus obtained sub- 

 tract the value for the creatinine content of the urine before dehydration. The 

 difference will be the creatine content of the original urine hi terms of creatinine. 



Interpretation. Creatine occurs only in very small amounts in the 

 urine of normal adults, but is found in larger amounts in that of children 

 (10 to 50 mg. per day). Creatine ingestion in adults has little effect 

 on the urinary excretion. In fasting, the amount is markedly increased 

 (it may amount to 100 mg. or more per day). Creatine also appears 

 in the urine after high water ingestion. It is found in many pathological 

 conditions associated with malnutrition and disintegration of muscular 

 tissue, in fever, etc. Very large amounts have been found in cases of 

 carcinoma of the liver. 



2. Folin-Benedict and Myers Method. 3 To 20 c.c. of urine in a 50 c.c. volu- 

 metric flask, add 20 c.c. of normal hydrochloric acid and place the flask in an auto- 

 clave at a temperature of ii7-i2oC. for one-half hour. Add distilled water until 

 the volume of the acid-urine mixture is exactly 50 c.c., close the flask by means of 

 a stopper, and shake it thoroughly. Approximately neutralize 25 c.c. of this mix- 



1 Benedict: Jour. Biol. Chem., 18, 191, 1914. 



2 The Rochelle salt should be present to prevent any formation of turbidity, which 

 otherwise may occur, due to the presence of traces of dissolved lead. 



3 Benedict and Myers: Am. J. Phys., 18, 397, 1907. 



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