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Notes: Dans le cadre de travaux concernant la barrière cutanée et ses modifications, notre but a été d'évaluer objectivement, in vivo chez l'homme, la réponse pharmacologique obtenue après application topique de deux réactifs vasoactifs: le nicotinate de méthyle (NM) et le nicotinate d'hexyle (NH). Deux méthodes non-invasives ont été comparées, la vélocimétrie laser Doppler, par deux appareils: le Periflux PF2 (Perimed, Suède), et le Laser Flo BPM 403 (TSI, USA), et la chromamétrie (Chromamètre CR 200, Minolta, Japon), à l'aide de quatre paramètres: le temps de latence précédant l'apparition de la réponse, l'intensité maximale de cette réponse, le temps pour atteindre cette intensité et le pourcentage de sujets répondeurs présentant une augmentation du flux sanguin cutané et/ou une rougeur cutanée. La vélocimétrie laser Doppler pose le problème de l'effet solvant et/ou sonde, ce qui rend délicate l'interprétation des résultats. C'est pourquoi nous avons choisi la chromamétrie pour apprécier, à l'aide de vasoactifs appropriés (NM dans l'eau et NH dans divers solvants), l'état de la barrière cutanée et son évolution après agression physique par stripping d'intensité croissante.〈section xml:id="abs1-2"〉〈title type="main"〉SynopsisWithin the framework of our research on the cutaneous barrier functions and their modifications, our objective was to estimate, in vivo in humans, the pharmacological response induced by the topical application of two vasoactive drugs: methyl nicotinate (MN) and hexyl nicotinate (HN). Two noninvasive methods were compared: laser Doppler velocimetry (LDV) (with two different types of equipment: Periflux PF2™ (Perimed, Sweden) and Laser Flo BPM 403™ (TSI, USA) and chromametry (Chromameter CR 200, Minolta, Japan). Four parameters were measured and/or calculated: the lag time before the first response, the highest intensity of the response, the time to reach this intensity and the percentage of sites responding with an increase of blood flow and/or a skin redness. Laser Doppler velocimetry shows a problem with the effect of the solvent and/or probe which makes the interpretation of the results difficult. With the vasoactive drugs, MN in water and HN in various solvents, chromametry was preferred for estimating the cutaneous barrier function and its evolution after physical aggression by progressive stripping of the horny layer.

Notes: This study investigated the effect of different treatments on skin permeability, in vivo in man, by two noninvasive methods: transepidermal water loss (TEWL) determination measured with an evaporimeter, and Laser Doppler velocimetry (LDV) to measure the lag time before the vasodilatation induced by application of methyl and hexyl nicotinates.Different treatments were performed on forearms of volunteers: 1. removal of the stratum corneum by stripping, 2. occlusion and hydration of the stratum corneum, 3. application of three surfactants in aqueous solution (Tween 60, sodium dodecyl sulphate and cetyl trimethylammonium bromide).Increase in TEWL and decrease in lag time before the vasodilating effects of nicotinates measured with LDV after all treatments confirmed the modifications in skin permeability. The variations observed were more or less significant depending on the treatment, the investigative method, and the molecule used for the penetration study. With methyl (hydrophilic) nicotinate, the more TEWL increased, the more lag time decreased. A significant decrease in lag time after hexyl (lipophilic) nicotinate application was observed when there was a very high increase in TEWL. The lipophilic nature of the stratum corneum barrier was confirmed in vivo. Use of these two complementary methods, TEWL and LDV, allows the evaluation in vivo of the effect of different treatments on skin permeability in man.