The influx of pyrophosphate ions into calvaria in vitro

Abstract

The flux of³²P-labeled inorganic pyrophosphate (PP_i) into bone was studied in vitro using Ussing chamber techniques and calvaria from newborn rat pups. Because insignificant hydrolysis and backflux of PP_i took place under experimental conditions, it was possible to study the penetration of bone membranes by PP_i unambiguously. At physiological concentrations, the influx was found to be linearly concentration dependent and to follow first order kinetics, apparently a simple diffusion process. In magnitude, the intrinsic constant for influx was found to be approximately one-half that of inorganic phosphate ions under comparable conditions.