Our aim was to determine the tissue distribution of CYP4F8, which occurs in human seminal vesicles and catalyzes 19-hydroxylation of prostaglandin H(1) and H(2) in vitro (J. Bylund, M. Hidestrard, M. Ingelman-Sundberg, E.H. Oliw, J. Biol. Chem. 275 (2000) 21844-21849). Polyclonal antibodies were raised in rabbits against RVEPLG, the C-terminal end of CYP4F8, and purified by affinity chromatography. Screening of 50 human tissues for CYP4F8 immunoreactivity revealed protein expression, inter alia, in seminal vesicles, epidermis, hair follicles, sweat glands, corneal epithelium, proximal renal tubules, and epithelial linings of the gut and urinary tract. The CYP4F8 transcripts were detected by reverse transcription polymerase chain reaction and by Northern blot analysis. There was a prominent induction of CYP4F8 immunoreactivity and mRNA in psoriasis in comparison with unaffected epidermis of the same patients. The cDNA of CYP4F8 from plucked scalp hair roots was identical with the genital cDNA sequence. We conclude that CYP4F8 is present in epithelial linings and up regulated in epidermis of psoriatic lesions.