[Influence of laurocapram on ultrastructures of mouse skin and sarcoma 180 membrane]

Laurocapram (Lau), 1-dodecyl-hexahydro-2 H-azepin-2-one, (azone) is a new percutaneous penetration enhancer. However, the mechanism of its action for absorption promoter of other agents is still unknown. In this paper the effect of Lau on ultrastructures of skin surface and tumor cell membrane were studies. Lau (2%) suspension was applied to abdominal skin of ICR/JCL, C 57 BL mice or one side of abdominal skin of nude mouse with drug and other side with the vehicle solvent once daily for 2-3 d. The skin was excised at 4 h after the final medication for examination under scanning electron microscope (SEM). The results showed the numerous small infolding lines which divided the skin surface into small areas with vesiculation and peeled the epidermal surface to form a few minor holes. The cuticles of the hair shaft dropped off and became thinner. Numerous desquamated cells around the orifice of the hair were fractured, detached and widened. Sarcoma 180 cells were incubated with Lau 25 micrograms/ml at 37 degrees C for 4 h. The microvilli of some cells dropped off and the size of villi became thinner and shorter. The top of some villi of the cells appeared occasionally thick to make the profile as a bat. The surface of numerous naked cells became rugged and rough and showed many black minor holes in the area of denuded cell membrane or dropped microvilli. More than 100 holes in the exposed surface of the naked cell were seen. It seemed that the Lau drilled holes on the biomembrane and enlarged the orifice of hair follicles and thus enhanced the transdermal absorption.