Cyclic changes in the metabolism of estradiol by rat skin during the hair cycle

Etude de l'action d'un traitement par voie topique sur la synthèse de la kératine pilaire chez le Rat

Synopsis Effect of topical treatment on pilar keratine synthesis in the rat The synthesis of keratin in pre-pubic Wistar rats has been studied under the influence of topic application of a lotion containing vegetable extracts. Changes of keratin synthesis in the rat was judged by the incorporation of a tagged precursor in the rat hair: cystein S-35 administered orally. Two protocols were followed each giving similar results. The first method concerned the regularity of hair growth with one sample taken per animal, and the second required multiple sampling in the same animal. Treatments with daily applications were in the range of 7-21 days. Results were analysed statistically in comparison with untreated zones. The excipient was tested separately in parallel. This rigorous procedure was essential, since the variations between individuals was wide in spite of the rats having been selected from the same litter. Daily application of the lotion showed an increase starting on the seventh day of the synthesis of keratin; the activity of the hair samples was already increased at this time by 90 to 400% (0.05>P>0.01). After 15 days increase reached > 1000% (P<0.05). Increase found for rats treated with the excipient do not reach significance. The hair growth cycle being 21 to 30 days, further continuation of the treatment gave only relatively weak stimulation of the keratin synthesis, the passage into the telogen phase slowing the synthesis of keratin whether it was produced from bulbar pre-keratin or synthesised in the hair itself.

A pharmacological effect of oestrone on human epidermis

Oestrone has been found to depress the incorporation of tritiated thymidine, proline and histidine in human skin in vitro. The significance of this is briefly discussed.

Metabolism of testosterone 4-14C in skin of castrated rats

Testosterone metabolism was studied in the skin and preputial glands of normal and prepuberally castrated male rats during the 2nd hair cycle. In catagen-telogen the 17-beta-OHSDH of dorsal skin was higher in castrated than in control animals; 5-alpha-reductase instead, remained unchanged through out the hair cycle. Also in the preputial glands of castrated rats 17-beta-OHSDH was higher than in normal rats. So was 5-alpha-reductase. A possible direct control of a substrate, like Testosterone, and/or of a hypophyseal tropin, like prolactin, on enzymes that direct the metabolism of steroids in target tissues is conceivable.

Adenyl-cyclase activity in rat-hair-cycle

In the skin of rat, during telogen phase, a high adenyl-cyclase activity coincides with maximal catecholamines content, minimal histamine level and blocking of mitoses in epithelial cells. These events suggest that in telogen the control of mitotic activity in rat hair follicles may operate through a block of G1 cells as already suggested for epidermal cells.