Diffusion of 133Xe through frog skins, toad bladders, and water boundary layers

We have measured the total permeability coefficients P as a function of stirring frequency ω for 133Xe through frog skins and toad bladders. The permeability coefficients for the frog skins and toad bladders proper are, respectively, P/sub m/ = (3.9 +- 0.8) x 10-4 cm/s and (7.4 +- 4.2) x 10-4 cm/s. ''Unstirred'' water layer thickness delta is determined concurrently, from the frequency dependence of P(ω); the result for frog skin is delta = (0.060 +- 0.016)/√ω(rad/s) cm. The stirring frequency range is from ω = 7.5 rad/s (72 rpm) to 55 rad/s (530 rpm). The results support the conclusions that the principal barrier to Xe diffusion in these epithelia is inter- and intracellular water, and that the diffusion is passive and rapid. The experimental method may be straightforwardly adapted to the measurement of diffusion or counterdiffusion of any gamma-radioactive soluble or partly soluble solute through any flat membrane or through a solvent. We estimate the amount of total body-absorbed radioactivity due to environmental 133Xe to be 50 fCi for an ambient concentration of 2.6 pCi/m3 of air