Quantitative evaluation of urea in stratum corneum of human skin

✍ Scribed by K. Wellner; W. Wohlrab

• Publisher: Springer-Verlag
• Year: 1993
• Tongue: English
• Weight: 233 KB
• Volume: 285
• Category: Article
• ISSN: 0340-3696
• DOI: 10.1007/bf00372018

✦ Synopsis

Urea, as a final product of protein metabolism, is a physiological substance in the human organism. The elimination of urea in humans amounts to 30 g per day; the amount in urine is of the order of 2% and in the blood 250 mg per ml. The urea content of human skin is about 1%.

Urea, as one of the natural moisturizing factors, influences the capacity of the horny layer to bind water and it also has keratoplastic, penetration-promoting, antimicrobial and antipruritic properties. Therefore, the observation that pathological skin alternations are accompanied by alterations in the content of urea is not unexpected. This has been studied and confirmed previously by several investigators using various analytical methods. Schwarz determined urea in aqueous extracts of scrapings from the horny layer of healthy volunteers and of patients with atopic dermatitis or psoriasis using thin layer chromatography followed by detection with Ehrlich's reagent [6] and, in a separate study, using an amino acid analyser [7]. For the investigation of urea content in aged skin Kfigelgen and Schwarz [5] also used an amino acid analyser. The amount of urea in callus was determined by Jacobi [3] using urease [1].

The procedure applying the amino acid analyser permits a determination of urea values only related to the part of amino acids. A disadvantage of all the methods previously described is that, in using scrapings from the horny layer, only the very superficial parts of the stratum corneum are considered.

The analytical method described here allows the quantitative evaluation of urea in absolute values over the whole thickness of the horny layer in a defined area of 2.5 cm 2. The method was selected using the following die critera: