B2.3 MINOXIDIL SULFOTRANSFERASE AND THE HAIR GROWTH RESPONSE

Andrew Messenger

Department of Dermatology, Royal Hallamshire Hospital, Sheffield, UK

The vasorelaxant effect of minoxidil is due to the action of its sulfated metabolite, minoxidil sulfate, as a potassium channel opener. Evidence from in vitro studies suggests that its effect on hair growth is also due to minoxidil sulfate. Minoxidil is sulfated by a group of enzymes known as sulfotransferases, some of which are expressed in the hair follicle. The level of platelet sulfotransferase activity shows wide inter-individual variation, which led the hair research group at the Upjohn Company to question whether differences in minoxidil sulfation could be a factor in determining its variable effect on promoting hair growth.

Fourteen men who had participated in a clinical trial of minoxidil lotion were studied, 6 responders in whom hair counts had increased by more than 50 in a defined scalp area, and 8 non-responders who had less than 10 new hairs. Minoxidil sulfotransferase activities were measured in homogenates of 4mm scalp biopsies and in platelet homogenates from each of the subjects.

The total and thermal labile minoxidil sulfotransferase activities in scalp skin homogenates were significantly higher (p<0.01) in responders than non-responders. Platelet enzyme activities were also higher in responders but lacked statistical significance.

Although the number of subjects in this study was small the results are encouraging. The hypothesis needs to be confirmed by including measurement of minoxidil sulfotransferase activity in future large-scale clinical trials.