Evaluation of inositol phosphates in urine after topical administration of myo-inositol hexaphosphate to female Wistar rats

F. Grases, A. Costa-Bauzá, F. Berga, A. Rodríguez, R.M. Gomila, G. Martorell, M.R. Martínez-Cignoni

Previous studies demonstrated a remarkable increase of urinary InsP6 by topical administration. However, the methodology used for InsP6 analysis was not specific. The aim of this paper is to measure urinary inositol phosphates InsPs using more advanced methodologies and to compare the results with those obtained by the non-specific method. We fed 12 female rats with a diet without InsP6 for 16days. Then, we administered a topical InsP6 gel at high doses for 7days (50mgInsP6/day) or at low doses for 28days (20mgInsP6/day). We measured urine levels InsPs using a nonspecific method (based on the ability of InsPs to complex Al3+) and levels of InsP6 by a specific method (using polyacrylamide gel electrophoresis). Identification of different InsPs was performed by MS. At baseline, after dietary deprivation of InsP6, rats only excreted InsP2 in their urine, and there was no detectable InsP6 or other InsPs. Rats given the high dose treatment for 7days had abundant urinary InsP6, but also had other InsPs in their urine; cessation of InsP6 administration led to decreased levels of urinary InsPs. Rats given the low dose treatment for 28days had increasing levels of urinary InsPs over time. The maximum urinary InsP6 was at 21days, after which InsPs excretion decreased. We conclude that the skin can absorb InsP6 from a topical gel, and that InsP6 is excreted in the urine, along with other InsPs (InsP5, InsP4, InsP3, and InsP2).