Stimulative effect of Ba2+ on p-aminohippurate transport in rat kidney cortical slices

BaCl2 stimulated significantly p-aminohippurate (PAH) accumulation in rat kidney cortical slices. The accumulation, however, was not stimulated by Sr2+, Mn2+ and Mg2+. Pretreatment of the slices with Ba2+ also increased PAH accumulation in the slices during incubation without BaCl2. Kinetical analyses of PAH accumulation showed that the effect of Ba2+ was to increase Vmax. No evidence for the effect of Ba2+ on PAH efflux from the slices was obtained. Thus, evidence indicating that Ba2+ stimulated PAH influx to the kidney cell was presented. Water distribution and energy metabolism in the slices were not related to the stimulative effect of Ba2+ on PAH accumulation. Ba2+ slightly lowered Na+ concentration in the slices. However, in the presence of ouabain, further addition of Ba2+ recovered PAH accumulation to a control value in spite of poor Na+ gradient as compared with that in control slices. Therefore, it is suggested that stimulation of PAH accumulation by Ba2+ was not due to changes in Na+ gradient. No stimulation of tetraethylammonium (TEA), an organic base, transport system by Ba2+ was observed. These data suggest that Ba2+ specifically stimulates the organic acid transport system in rat kidney cortical slices by increasing PAH influx to the cells.