Effect of substrates on potassium accumulation by rabbit kidney cortex

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Abstract
Slices of rabbit renal cortex were depleted of potassium by leaching for 30 minutes in 0.15 m sodium chloride solution. The ability of various substrates to promote reaccumulation of potassium was studied by incubating the leached slices with substrate at 37.5 C in a K-rich medium. Of the ten substrates studied, glutamate, glutamine, and α-ketoglutarate supported K uptake best, permitting the tissue during 40 minutes of incubation to attain K concentrations almost equal to the concentrations in fresh tissue. Glucose was comparable to the above three substrates at 40 minutes, but the initial rate of uptake was slower. With fumarate, oxalacetate, malate, and succinate the K uptake was not significantly greater than in experiments where no substrate was employed. Citrate and aspartate supported K uptake better than no substrate, but not as well as glutamate, glutamine, and α-ketoglutarate. When α-ketoglutarate was used as the substrate the addition of magnesium improved the K uptake. The relationship between K uptake and Na extrusion is discussed.