Isotretinoin differs from other synthetic retinoids in its modulation of human cellular retinoic acid binding protein (CRABP)

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Abstract
Isotretinoin differs from acitretin and ROI374IO by its striking sebostatic effect in acne after oral, but not topical, administration. The reason for this is not yet understood. Previous studies indicate that cellular retinoic acid binding protein (CRABP) might be implicated in the action of synthetic retinoids. We, therefore, compared the three retinoids for their ability to increase epidermal CRABP levels after systemic and topical treatment. Oral treatment with acitretin and ROI374IO led to a striking increase of epidermal CRABP (from 2.6 .+-. 0.9 to 16.2 .+-. 2.9, P<0.004 and from 2.5 .+-. 1.23 to 21.5 .+-. 3.4 pmol/mg protein, P<0.004, respectively), while isotretinoin failed to induce a comparable rise (3.2 .+-. 1.6 before and 3.7 .+-. 0.7 pmol/mg protein after treatment), although it displayed in all patients a striking sebostatic effect. After topical application, the increase of CRABP was comparable for all three compounds. The interaction of isotretinoin with the epidermis seems to be different from other synthetic retinoids only after systemic treatment, a finding that parallels clinical observations.