Myo-inositol hexakisphosphate (InsP 6 ) is an abundant component of plant seeds. In whole grain cereals it ranges from 1.5 to 6.4% and it is mostly associated with calcium and magnesium ions, the so-called phytin. 1,2) Recently it was found that InsP 6 is also present in all mammalian organs, tissues and fluids but at significantly low amounts. Moreover, it was demonstrated that the levels found in biological fluids (blood, urine, interstitial liquid) and mammalian tissues clearly depended on the dietary intake. [3][4][5] Diverse studies performed by Mellanby demonstrated that a high InsP 6 content in some diets, as sodium salt, reduced calcium absorption and induced rickets. 6) Ever since up to now, several studies have attributed "anti-nutritional" properties to phytate. [7][8][9][10][11] Nevertheless, other studies [12][13][14][15][16] have shown that those findings are not quite so clear and simple as mentioned. Moreover, from the 1980s to the present, important physiological functions of InsP 6 have been suggested as its properties as an antioxidant 17,18) and its role in colon cancer prevention. 19,20) The InsP 6 present in urine and biological fluids also exhibited an important role in preventing pathological calcifications as renal calculi [21][22][23] or calcinosis cutis, 24) due to its powerful capacity to act as crystallization inhibitor of calcium salts.Finally, the most recent observations about the properties of InsP 6 are related to its dermatological use. The majority of those applications are referred to their important action on premature aging or as discolouring agent of the skin.25) Also some studies seem to demonstrate a capacity of InsP 6 to inhibit skin cancer. 26,27) In the present paper a first study of the absorption of InsP 6 through the skin is developed.
MATERIALS AND METHODS
Animals, Diets and Experimental DesignTwenty-four female Wistar rats of approximately 225 g from Harlan Iberica s.l. (Barcelona, Spain) were acclimated in the course of 7 d to our animal house. Animals were kept in Plexiglas cages (two animals per cage) at a temperature of 21Ϯ1°C and relative humidity of 60Ϯ5% with a 12-h on-off light cycle. After this period, animals were randomly assigned into four groups of six rats respectivelly. Rats were fed with 4068.02 Reference Diet (HopeFarms BV, Woerden, The Netherlands), a synthetic purified diet (Table 1) in which InsP 6 is undetectable.After a period of 16 d consuming such diet, during which the urinary InsP 6 became undetectable, rats were topically treated once a day with 4 g of a standard cream with a supplement of 0.4, 1.2 and 2.0% of InsP 6 as sodium salt or 2.0% of InsP 6 as calcium magnesium salt (phytin). The surface of treatment was about 50 cm 2 . The application area was located on the back skin of the animal and was previously shaved using an electric shaver (each 4 d). During cream treatment animals were located individually to avoid licking cream. pH of all creams was adjusted to 4-4.5 (see Table 2). Samples of 24-h urine were collected at days 0, 7 ...