The composition of lipids existing in hair, epidermis and dermis of rat was analyzed by thin-layer chromatography and the composition and amount of sterols were determined by gas-liquid chromatography.
The major constituent of the hair lipids was sterol esters and the sterol fraction (21.4mg/100g body wt.) consisted of 26.6% cholesterol and 44.9% lathosterol. On the other hand, in epidermis and dermis, the main component of the lipids was triglyceride. Cholesterol and lathosterol composed 49.7% and 21.6% of the sterol fraction, respectively, and the total amount of sterols was 43.9mg/100g body wt.
In the sterol fraction of the lipids of the other organs, there existed predominantly cholesterol (96.4%) and a small amount of plant sterols (campesterol and β-sitosterol) was observed.
The proportion of sterols existing in the skin including hair was 36.1% of the total sterols in whole body, which was about 28 times larger than that of serum cholesterol pool. Since the wet weight of the skin was 17.4% of whole body, it was concluded that the sterol concentration in the skin was higher than the mean concentration in the other organs.
These results indicated that the skin lipids might play an important role in the lipid metabolism of whole body. Although many investigators have studied the effects of hypolipidemic drugs in rat on the lipid levels in serum and liver and on the excretion of sterols and bile acids into bile or feces, the effect of drugs on the skin lipids must be examined as well.
