Distribution of various nickel compounds in rat organs

Human stratum corneum (SC) was prepared by trypsinization of dermatomed cadaver leg skin. The diffusion system included diffusion cells with a spiral line. Aqueous solutions of nickel salts (Ni(NO3)2, NiSO4, NiCl2 and Ni(-OOCCH3)2 at 1% Ni2+ concentration) were used as the donor solution (400 microL/cell). The receptor fluid, pure water, was collected up to 96 h after application of the donor solutions. Nickel concentrations in the donor and receptor fluid, as well as in the SC, were analysed using inductively coupled plasma mass spectrometry (ICP-MS) with a confidence limit of 0.5 ppb. Based on the total recovery of nickel from the experiments, about 98% of the dose remained in the donor solution, whereas 1% or less was retained in SC and less than 1% was found in the receptor fluid. Following an early surge, nickel permeates slowly across SC. The steady-state permeability coefficients of nickel were calculated from the flux data (approximately 5.2-8.5 x 10(-7) cm/h) with no significant difference among the salts. The results concur in principle with earlier studies conducted using the full-thickness human skin in vitro, and suggest that in vivo nickel ions may permeate simultaneously by routes of diffusion such as the shunt pathway, apart from slow transcellular/intercellular diffusion alone.