Principle of the Procedure

Creatinine (Cr) is a metabolic product of muscle in the body and is mainly eliminated through glomerular filtration by the kidneys. The creatinine present in blood originates from both exogenous and endogenous sources. Exogenous creatinine is derived from the metabolism of meat-based foods, while endogenous creatinine is produced from the metabolism of muscle tissue within the body.

Blood creatinine is almost entirely filtered by the glomeruli into the primary urine and is not reabsorbed by the renal tubules. The daily production of endogenous creatinine remains nearly constant. When exogenous creatinine intake is strictly controlled, the blood creatinine concentration remains stable. Therefore, determination of blood creatinine concentration can reflect glomerular filtration function.

This kit provides a simple and convenient colorimetric method for the determination of creatinine content in samples. The assay principle is as follows: creatininase catalyzes creatinine to produce creatine; creatinase then catalyzes creatine to generate sarcosine and urea. Sarcosine is oxidized by sarcosine oxidase to produce hydrogen peroxide. In the presence of peroxidase, hydrogen peroxide oxidizes 4-aminoantipyrine coupled with phenol to form a red quinone compound, which exhibits a characteristic absorption peak at 500 nm. Measurement of absorbance at 500 nm allows quantification of creatinine in the sample.