In vitro renal transport of organic ions during exposure to hyperbaric helium

The possibility that hyperbaric helium can modify membrane function in nonneural cells was investigated by measuring the effect of pressure (29.6 atm He + 1.0 atm O2) on transport of the organic anion p-aminohippurate (PAH) and the organic cation tetraethylammonium (TEA) by renal cortex slices. Control slices were exposed to 100% O2 at 1 ATA. A unique incubating and shaking apparatus was built to allow remote control of the incubation conditions in a sealed chamber containing hyperbaric O2. In rat or rabbit renal tissue incubated for 90 min, pressure did not affect the uptake of either substance and was without effect on the total water content and inulin space of rat renal cortex. The kinetic characteristics of the transport systems were investigated by incubating tissue for 15, 30, 45, 60, 75, or 90 min. These experiments were analyzed by fitting a mathematical model to the data and calculating values for parameters representing the active and passive components of the transport processes. Pressure did not affect either of the parameters for PAH or for TEA transport. Thus, if helium elicits its known neural effects through an action on cell membranes, that action is not large enough to be detected by this assay system.