Hair Loss > Rogaine / Minoxidil > Hairloss Study Abstract: Minoxidil sulfate is the active metabolite that stimulates hair follicles.
Hairloss Study Abstract: Minoxidil sulfate is the active metabolite that stimulates hair follicles.
Title
Minoxidil sulfate is the active metabolite that stimulates hair follicles.
Author
Buhl AE, Waldon DJ, Baker CA, Johnson GA
Address
Upjohn Company, Kalamazoo, Michigan 49001.
Source
J Invest Dermatol, 95: 5, 1990 Nov, 553-7
Abstract
An important step in understanding minoxidil's mechanism of action on hair follicles was
to determine the drug's active form. We used organ-cultured vibrissa follicles to test
whether it is minoxidil or its sulfated metabolite, minoxidil sulfate, that stimulates
hair growth. Follicles from neonatal mice were cultured with or without drugs and effects
were assessed by measuring incorporation of radiolabeled cysteine in hair shafts of the
treated follicles. Assays of minoxidil sulfotransferase activity indicated that vibrissae
follicles metabolize minoxidil to minoxidil sulfate. Dose-response studies showed that
minoxidil sulfate is 14 times more potent than minoxidil in stimulating cysteine
incorporation in cultured follicles. Three drugs that block production of intrafollicular
minoxidil sulfate were tested for their effects on drug-induced hair growth.
Diethylcarbamazine proved to be a noncompetitive inhibitor of sulfotransferase and
prevented hair growth stimulation by minoxidil but not by minoxidil sulfate. Inhibiting
the formation of intracellular PAPS with chlorate also blocked the action of minoxidil but
not of minoxidil sulfate. Acetaminophen, a potent sulfate scavenger blocked cysteine
incorporation by minoxidil. It also blocked follicular stimulation by minoxidil sulfate
apparently by directly removing the sulfate from the drug. Experiments with U-51,607, a
potent minoxidil analog that also forms a sulfated metabolite, showed that its activity
was inhibited by both chlorate and diethylcarbamazine. These studies show that sulfation
is a critical step for hair-growth effects of minoxidil and that it is the sulfated
metabolite that directly affects hair follicles.