Zur wirkungsweise der vitamin a-s�ure (tretinoin)

The local treatment of hypertrophic scars and keloids with topical retinoic acid

In a clinical trial twenty-eight intractable cases with scars were treated with daily applications of a 0.05% solution of retinoic acid. The results were evaluated objectively and subjectively. Slight to marked reduction of the size of these scars and decrease of such complaints as itching were noted in the majority of the cases. A favourable result was obtained according to the patients in 79%, and according to the opinion of the medical examiner in 77% of the patients.

Effects of retinoic acid on embryonic chick skin

The influence of vitamin A on differentiating epithelia was examined in explants of skin from 14-day chick embryos exposed to retinoic acid (RA) in low, moderate, and high doses. The changes observed in RA-treated cultures are both dose- and time-dependent and are reversible when explants are transferred to control medium. The periderm sloughs prematurely and horizontal stratification is lost. Keratinization is inhibited and fewer desmosomes and tonofilaments are seen. Surface epidermal cells develop microvilli, bulge upwards, and detach. Golgi elements, rough endoplasmic reticulum, and polyribosomes are unusually prominent. Mucin granules form and gland-like structures develop with intercellular canaliculi characterized by tight junctions, brush borders, and dense secretory contents. On the basis of present evidence there are several possible mechanisms by which RA could alter epidermal differentiation. RA-induced gaps in the basal lamina allow direct contact between epidermal basal cells and fibroblasts and collagen fibers which could result in inappropriate dermal signals reaching the epidermis. In younger embryos the entire epidermis, including the mitotically inactive surface cells, appears to respond to RA, and this could imply an epigenetic modulation of cell phenotype. Finally, after the formation of a stratum corneum in older embryos only the relatively undifferentiated basal layer shows a metaplastic response, indicating that RA could be acting directly on the genome.

Influences of retinoic acid and retinoid on skin metabolism. Investigations of oxygen consumption and enzymatic activities of human skin

All-trans retinoic acid and its derivative retinoid, two new compounds with expanding therapeutic spectrum in dermatology, were investigated in biochemical assays. Both substances provoke an increase in oxygen consumption of rat skin whereas in human skin only retinoid was found active in this respect. In resting yeast cells, both substances failed to exert any significant influence on oxygen consumption.--Pure G-6-PDH was inhibited by retinoic acid and retinoid in concentrations as low as 5 mug/ml. In human skin homogenates, LDH-, GAPDH-, and G-6-PDH-activities were inhibited by retinoic acid whereas GOT-, LAP-, and ALD-activites remained practically unchanged following an incubation with retinoic acid in concentrations between 1 and 100 mug/ml for 60 min.--The data collected in this study were briefly discussed with regard to the use of retinoic acid and its derivatives in psoriasis.

Allergic contact response to vitamin A acid

Three patients treated daily with vitamin A acid cream experienced after one week, seven weeks and 14 weeks respectively sudden redness and itching at the treated sites. Patch testing with the cream (containing 0.05% vitamin A acid) and with vitamin A acid 0.05% in absolute alcohol produced strongly positive reactions in the patients but only slight erythema in some of the controls. Since patch testing with vitamin A acid 0.005% in absolute alcohol elicited no response in controls but positive reactions in the three patients, it is probable that these latter reactions were due to contact allergy. Histologically the test reaction showed intact epidermis and dense dermal infiltration by mononuclear cells, and thus resembled a response of the tuberculin type.