Coarse to fine hair conversion induced by zinc in C57/6J mice.

The cytotoxic effects of excessive zinc is well documented but its effect on cytodifferentiation appears relatively unknown. We show here that chronic administration (25 days) of zinc chloride in C57/6J mice (11 to 56 micrograms/g body weight, 5 times per week), which was lower than the in vitro cytotoxic level, caused a loss of long coarse hairs, which were replaced by short fine (vello) hairs. Histological architecture of the skin appeared normal except for the confinement of hair follicles to the dermis without any extension into the hypodermis.