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EC number: 231-944-3 | CAS number: 7779-90-0
Radiocounts of 65Zn:
-Optimal activity was observed at 6 h after each application; reduced at 24 h after application of first or second dose (see table 1).
- High concentration was observed in the cortical and cuticular zones of the hair shaft, optimal in the keratogeous zone
- 65Zn localisation was very low in the epidermis, dermis and in blood vessels of both dermis and hypodermis
- Optimal staining intensity was seen in the cortex of the hair shaft and in the keratogenous matrix of the hair papilla
Table 1. 65Zn Retention on excised skin blocks (cpm X 103)*
Total applied dose of Zn compound
Time after last application
Zinc oxide (Single dose)
Zinc oxide (double dose)
* Results corrected for background and counted simultaneously with an aliquot of the applied sample. Second dose was always applied 24 h after the first application.
ZnO, zinc omadine, zinc sulphate and zinc undecylenate (131mCi/mole of65Zn2+) were used for topical application on shaved skin on the back of rabbits. Each application consisted of 2.5 mg Zn-compound containing 5mCi65Zn2+. Two animals received one application on four skin areas left of the spine, while the four skin areas on the right side received two applications, the second one 24 hours after the first one. The rabbits were killed 6 and 24 hours after the second application. One rabbit served as control animal.
No significant differences were found in the amount and location of 65Zn2+in skin treated with 4 different zinc compounds. High concentrations of 65Zn2+were observed in the cortical and cutical zones of the hair shaft, being the highest in the keratogenous zone. Accumulation of65Zn2+in epidermis was very low but heavy in the subdermal muscle layer. Since no different rates of absorption and concentrations of zinc compounds with different oil/water solubility, pH, and molecular weight were seen, it was suggested that the major mode of65Zn2+uptake in skin is by diffusion through the hair follicles due to the heavy localization of65Zn2+primarily in the hair shaft and hair follicles. According to the investigators this emphasizes that chemical differences in the compounds may not play a very important role in the skin uptake of65Zn2+. No data were given on systemic absorption.
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