Figure 2. •icro•utor•iogr•ms showing the •istribution topical •pplic•tion o[ •C-l•bcllc• oils. i) iPM, 2) GTO, •) OD, 4) DD, S) HDO •n• A) d hr, B) 24 hr (scc text) 270

PERCUTANEOUS ABSORPTION OF COSMETIC OILS 271 Figure 3. Microautoradiograms showing the distribution of radioactivity in the skin of Angora rabbits after topical application of 14C-IPM. A) intact skin, B) 2 hr, C) 6 hr, D) 24 hr. Note the concentration in the se- baceous glands and epidermis MICROAUTORADIOGRAPHY AND HISTOLOGY WITH ANGORA RABBITS The distributions and skin irritation potentials of •4C-labelled IPM and HDO were examined by microautoradiography and histological method in the skins of Angora rabbits sacrificed at 2, 6 and 24 hr after topical application. IPM. 1. Microautoradiography: after 2 hr, the silver grains were already observed sparsely in the hair follicles and th• t•pidermis, especially centered in the sebaceous glands. Then the grains became con.•entrated during the period of applicat•.on. The dermis adjacent to the sebaceous glands and beneath the epidermis had an increasing distribution of grains with the time course (Figure 3). 2. Histology: histological changes due to IPM were not intense at 2 and 6 hr. The infiltration of polymorphonuclear leucocytes was observed in the hair follicles. and the collagen fibers under the epidermis were seen to become fine. Also, the infiltration of small mononuclear and polymorphonuclear leucocytes into the upper layers of dermis was slightly observed. After 24 hr, the epidermis was thickened to three or four cell layers. The epidermal cells became swollen and round. Vacuolation around nuclei was also observed. The keratohyalin granules disappeared in a wide area so that the stratum comeurn was thinned. The sebaceous glands became larger. In the dermis, the collagen fibers became fine and marked vasodilatation was seen together with partial hemorrhage (Figure 4). HDO. 1. Microautoradiography: after 2 hr, the silver grains were observed in the se- baceous glands and the adjacent dermis. Then the grains over the sebaceous glands and