Urea is primarily produced in the liver and secreted by the kidneys. Urea is the major end product of protein catabolism in animals. It is the primary vehicle for removal of toxic ammonia from the body. Urea determination is very useful for the medical clinician to assess kidney function of patients. In general, increased urea levels are associated with nephritis, renal ischemia, urinary tract obstruction, and certain extrarenal diseases, e.g., congestive heart failure, liver diseases and diabetes. Decreased levels indicate acute hepatic insufficiency or may result from over-vigorous parenteral fluid therapy. Simple, direct and automation-ready procedures for measuring urea concentration or blood urea nitrogen BUN in biological samples are becoming popular in Research and Drug Discovery. BioAssay Systems' urea assay kit is designed to measure urea directly in biological samples without any pretreatment. The improved Jung method utilizes a chromogenic reagent that forms a colored complex specifically with urea. The intensity of the color, measured at 520nm, is directly proportional to the urea concentration in the sample. The optimized formulation substantially reduces interference by substances in the raw samples.

Simple and high-throughput. The procedure involves addition of a single working reagent and incubation for 20 min. Can be readily automated as a high-throughput assay for thousands of samples per day.

Improved reagent stability and versatility. The optimized formulation has greatly enhanced reagent and signal stability. Cuvet or 96-well plate assay.

Low interference in biological samples. No pretreatments are needed. Assays can be directly performed on raw biological samples i.e., in the presence of lipid and protein.

Drug Discovery/Pharmacology: effects of drugs on urea metabolism.

Environment: urea determination in waste water, soil etc.

Precautions: reagents are for research use only. Normal precautions for laboratory reagents should be exercised while using the reagents. Please refer to Material Safety Data Sheet for detailed information.

Equilibrate reagents to room temperature. Prepare enough working reagent by combining equal volumes of Reagent A and Reagent B, shortly prior to assay. Use working reagent within 20 min after mixing.

Urea concentration (mg/dL) of the sample is calculated as

Conversions: BUN (mg/dL) = [Urea] / 2.14. 1 mg/dL urea equals 167 μM, 0.001% or 10 ppm.

Pipeting devices and accessories (e.g. 5 μL).

Clear bottom 96-well plates (e.g. Corning Costar) and plate reader.

Spectrophotometer and cuvets for measuring OD520nm and OD430nm.

Biological samples were assayed in duplicate using the 96-well protocol. The urea concentration (mg/dL) was 12.5 ± 0.9 for Commercial 2% reduced fat milk (Kirkland), 35.7 ± 0.1 for Invitrogen fetal bovine serum, 22.1 ± 0.9 for human serum, 22.3 ± 0.2 for human plasma, 31.8 ± 1.1 for rat serum, 42.6 ± 0.1 for rat plasma and 1501 ± 52 for a fresh human urine sample, 0.21 ± 0.03 in a human BAL sample, 0.15 to 2.7 mg/dL in cell culture.

1. Ji, H., Bachmanov, A.A. (2007). Differences in postingestive metabolism of glutamate and glycine between C57BL/6ByJ and 129P3/J mice. Physiol Genomics 31(3):475-82.

2. Snykers, S. et al (2007) Chromatin remodeling agent trichostatin A: a key-factor in the hepatic differentiation of human mesenchymal stem cells derived of adult bone marrow. BMC Dev Biol. 7:24.