Morphological and morphometrical study on the dorsal skin of Wistar and WBNIILA-Ht rats in their developing stage.

Abstract

The detailed histology of the dorsal skin of Wistar-derived hypotrichotic WBNIILA-Ht rats (HtRs) was examined in their developing stage (at 3 and 7 weeks of age) using Wistar rats (WRs) as controls. As a result, except for the existence of time-lag in the hair follicular cycle and some quantitative differences, there were no essential qualitative differences between the two strains. The follicular epithelial cell number and the amounts of tonofilaments and trichohyalin granules were less in HtRs than in WRs in the same phase of hair follicular cycle. In addition, the diameter of hair shaft was significantly larger in WRs than in HtRs at 7 weeks of age. The number of proliferating cell nuclear antigen (PCNA)-positive epidermal basal cells decreased in HtRs and increased in WRs from 3 to 7 weeks of age, respectively. Apoptosis was sparsely observed in the sebaceous gland epithelia1 cells, keratinizing portion of hair cuticules and inner root sheath in both strains, but the frequency of apoptosis in the hair follicle was somewhat higher in 7-week-old HtRs. HtRs are considered to be useful experimental animals for dermatotoxicological studies.