EFFECTS OF ALL-TRANS-RETINOIC ACID AND SODIUM LAURYL SULFATE ON THE PERMEABILITY OF HUMAN SKIN IN-VITRO

Recent in vivo investigations have shown that pretreatment with topica l all-trans retinoic acid (RA) may diminish the skin response to sodiu m lauryl sulphate (SLS), This study evaluated the permeation of SLS th rough human skin after pretreatment with RA, and vice versa, by in vit ro methods, The permeability coefficient of SLS (3.24 +/- 0.21 x 10(3) cm/h) and the 24-h cumulative amount of SLS 3.41 +/- 0.6% of dose app lied) permeating RA-pretreated skin did not differ significantly from those across untreated skin (control) (P > 0.05). In contrast, the per meability coefficient of RA (0.23 +/- 0.05 x 10(3) cm/h) and its 24-h cumulative amount (0.37 +/- 0.05% of dose applied) penetrating SLS-pre treated skin were significantly greater than these permeating untreate d skin (P < 0.05). Thus, an increase in RA penetration was induced by SLS pretreatment; however, pretreating the skin with RA did not inhibi t the percutaneous permeation of SLS. Based on previous in vivo findin gs where RA reduced skin reactions to SLS,(8) one would speculate that RA pretreatment may decrease SLS penetration. However, these penetrat ion data do not necessarily uphold this presumption. Perhaps, other in teractions between the substances and the skin, e,g, at cellular level s, may be responsible for the differing skin responses.