Significant variation in mouse-skin aryl hydrocarbon hydroxylase inducibility as a function of the hair growth cycle

An easy, rapid and improved technique for homogenizing whole skin is described. This technique consists of reducing skin to a powder in liquid N2 by using a metallic mortar, and homogenizing the powder in a Potter-Elvehjem tube. Using this homogenizing method, we have shown that skin AHH activity in C57BL/6K and C3H/Ico mice can be induced by i.p. injected or topically applied methylcholanthrene during a defined period of the hair growth cycle, i.e. between the 8th and 14th days after depilation (Stage 6 of the anagen period). In each experimental model, there is an optimal methylcholanthrene concentration which yields a maximum induction. Topical methylcholanthrene is also responsible for a smaller aryl hydrocarbon hydroxylase (AHH) induction when the chemical is applied the same day that the club hairs are plucked. On the other hand, skin AHH activity is never induced by methylcholanthrene in DBA/2J mice, a genetically non-responsive strain. No clear-cut segregation of skin AHH inducibility levels is found among the offspring from the back-cross between (C57BL/6J X DBA/2J)F1 and non-inducible DBA/2J mice.