[Investigations on the mechanism of the activity of urea upon the epidermis (author's transl)].

As a reaction of the epidermis subsequent upon contact with urea, a thinning is ascertainable 5 days later, for which corresponding enzymological and autoradiographical findings cause to presume the DNA being the working point. Further information about the mechanism of this reaction was obtained first by short time tests, whence by means of 3H thymidine autoradiography not later than the second day after contact with urea a decreased number of cells synthesizing DNA in the stratum basale were to be secured. These findings obtained using the model of the guinea-pig's ear are also ascertainable in the human skin, an unspecified effect, also to be released by other non-electrolytes, having been excluded by controls of glucose replacing urea. The quick invasion of urea into the epidermis, deducible from the short time tests, was proved by 14C traced urea, ascertainable not later than 15 min after its contact with the skin amongst the blood - even if in little activity. Hence, the urea enters into the cutis speedily, releasing there a disturbance in the process of the epidermal proliferation, which conducts in the sequel to an epidermal thinning.