Open AccessThe cell kinetics of the epidermis and follicular epithelium of the rat: variations with age and body site
Author(s) -
Morris G. M.,
Hamlet R.,
Hopewell J. W.
Publication year - 1989
Publication title -
cell proliferation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.647
H-Index - 74
eISSN - 1365-2184
pISSN - 0960-7722
DOI - 10.1111/j.1365-2184.1989.tb00207.x
Subject(s) - epidermis (zoology) , epithelium , basal (medicine) , biology , dorsum , dermis , anatomy , cell growth , medicine , endocrinology , biochemistry , genetics , insulin
The skin from rats of differing age was used to quantify variations in the cell kinetics of the epidermis and the follicular epithelium of different body sites. Four parameters were assessed, namely the basal cell density (BCD), the labelling index (LI), the duration of DNA synthesis ( t s ) and the basal cell turnover time ( t T ). The BCDs of the epidermis of the dorsum and the upper surface of the foot were similar in rats of 7, 14 and 52 weeks of age, but there was an indication of a progressive decline with increasing age in the BCD of the epidermis of the ear and tail. There were no age‐related changes in the length of t s in any of the four body regions. The rate of cell proliferation, as indicated by the values of the LI and t T , was relatively rapid in the epidermis of the dorsum, foot and tail of rats aged 7 weeks (LI > 12%; t T < 80 h). In rats aged 14 weeks this rate of proliferation was maintaned in the epidermis of the dorsum. However, in the foot and tail the rate of cell proliferation was decreased (LI < 10%; t T > 85 h). A fall in the rate of proliferation of the epidermis of the dorsum was only seen in 52‐week‐old animals. In these animals the rates of proliferation in the foot and tail were similar to those at the age of 14 weeks. In the epidermis of the ear there was no appreciable change in the rate of cell proliferation with age. The values of the cell kinetic parameters varied in the different body sites. For example, in 52‐week‐old animals values for t T were relatively short in the epidermis of the tail and foot and appreciably longer in the epidermis of the dorsum and ear. Considered overall, values for the cell kinetic parameters of the epidermis were comparable with those for the follicular epithelium. The only major differences between the epidermis and the follicular epithelium were in the upper surface of the foot at 7 weeks of age, and in the tail at 7 and 14 weeks of age, where the LI was higher and the t T shorter in the epidermis than in the follicular epithelium. The relevance of the observed age‐ and body‐site‐related variations in the cell kinetics of the epidermis are discussed in relation to previously described differential changes in the radiosensitivity of the skin in this strain of rat.