VALIDATION OF FREEZE-DRYING TO VISUALIZE PERCUTANEOUS H-3-ESTRADIOL TRANSPORT - THE INFLUENCE OF SKIN HYDRATION ON THE EFFICACY OF THE METHOD

A study was made of the validity of freeze-drying to visualize the dis tribution of H-3-estradiol in human stratum corneum after topical appl ication of a dry dose, a patch or a buffer solution. Each of these don or formulations was applied to human dermatomed skin for 24 h using Fr anz permeation cells. Subsequently, small pieces of skin were subjecte d to cryofixation, freeze-drying, osmium tetroxide vapor fixation, Spu rr resin embedding and electron microscopic autoradiography, Stratum c orneum from dry dose and patch application experiments was well preser ved by freeze-drying, allowing an accurate localization of H-3-estradi ol. In contrast, stratum corneum from buffer solution experiments suff ered from cryofixation artifacts due to excessive hydration of the ski n. The corresponding autoradiographs showed strong redistribution of H -3-estradiol. Thus, the visualization method under investigation has i ts limitations regarding the hydration level of the skin.