FATTY-ACID OXYGENASE ACTIVITY OF HUMAN HAIR ROOTS

The extent to which fatty acid oxygenases are activated in the normal epidermis is not known. Characterization of the regio- and stereospeci ficity of the monohydroxylated derivatives of arachidonic and linoleic acid produced by human hair roots is needed to define the enzymatic o rigin of these compounds and to define a possible role for fatty acid oxygenases in growth, differentiation, and pathology of human hair. Ha ir roots epilated from normal human volunteers were incubated with rad iolabeled arachidonic acid or linoleic acid and the monohydroxylated d erivatives produced in vitro were characterized. Incubation of hair ro ots with [C-14]arachidonic acid resulted in the production of 15(S)-[C -14]hydroxyeicosatetraenoic acid and 12(S,R)-[C-14]hydroxyeicosatetrae noic acid (mean S/R ratio, 2.5). 13(S)-[C-14]hydroxyoctadecadienoic ac id was the principal product of incubations With [C-14]linoleic acid. No radiolabeled products were derived from incubations with heat-denat ured hair roots. The fatty acid oxygenase activity of anagen hair root s was inhibited by nordihydroguaiaretic acid and was greatest in the h air root bulb. The strict S-stereospecificity and the regiospecificity of the n-6 oxygenase are strong evidence for the presence of a 15-lip oxygenase in human hair roots, similar to that identified in cultured human keratinocytes. The stereospecificity of the 12-HETE produced by human hair roots is not compatible with the sole action of 12-lipoxyge nase.