Electrophoretic variations of tyrosinase in follicular melanocytes during the hair growth cycle in mice

Multiple forms of tyrosinase separable by acrylamide‐gel electrophoresis are demonstrable in extracts of hair bulbs prepared on the fifth (anagen IV) through the thirteenth days (anagen VI) of a hair growth cycle induced in C57BL/6J mice by plucking of quiescent hairs. The enzymic bands visualized by incubation of the gels in L‐DOPA have been designated as T1, T2 and T3. Although T1 has been observed through day 19, the T2 and T3 components disappear by day 15 of the hair growth cycle. Tyrosinase activity is not demonstrable in skin extracts prepared during telogen or on days 1–3 post‐plucking (anagen I–III). The slow development of a single DOPA‐melanin band in such samples has been demonstrated to represent non‐specific oxidation by hemoglobin that migrates at a slightly slower rate than the T3 component. The precise state of tyrosinase within follicular melanocytes prior to day 5 of the hair growth cycle remains to be determined. The functional significance of the multiple forms of tyrosinase also is yet to be established.