EFFECT OF BARIUM ION ON PARA-AMINOHIPPURATE TRANSPORT IN BASOLATERAL MEMBRANE-VESICLES ISOLATED FROM RAT-KIDNEY CORTEX

  • 1 January 1985
    • journal article
    • research article
    • Vol. 275  (2) , 287-299
Abstract
The cause of the stimulation of p-aminohippurate (PAH) accumulation in rat kidney cortical slices by Ba was studied in an experiment carried out with basolateral membrane vesicles isolated from rat kidney cortex. The effect of Ba on PAH uptake by the membrane vesicles was compared with that of verapamil which also stimulated PAH accumulation in the slices. The enzyme marker for basolateral membrane, (Na++K+)-ATPase, was enriched 15-fold and the brushborder enzyme marker, alkaline phosphatase, was 1.3-fold in the membrane preparation. Contamination in this preparation by lysosomes, mitochondria and cytosol was also low but that by endoplasmic reticulum was slightly high as judged by the enzyme markers. PAH uptake by the membrane vesicles possessed the usual characteristics, i.e. Na-dependence and probenecid-sensitivity. PAH uptake by the membrane vesicles was enhanced by Ba, but not by verapamil. Ba did not affect tetraethylammonium (TEA) uptake by the vesicles, and verapamil strongly inhibited it. Mn stimulated PAH uptake to the same extent as did Ba, but Ca and Sr did not affect the uptake. Ba did not act on Na transport in the membrane vesicles. An anion-sensitively transported lipophilic cation, triphenylmethylphosphonium iodide (TPMP), uptake was depressed by Ba. Ba apparently selectively stimulates PAH uptake in basolateral membrane vesicles. Its stimulatory action may contribute at least partly to an increase in PAH accumulation in rat kidney cortical slices by this ion and may prove useful in an analysis of the mechanism of PAH transport system in renal basolateral membranes.