Effects of renal fuels on uptake of PAH and uric acid by separated renal tubules of the rabbit

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Abstract
A rapid-filtration procedure was used to examine effects of a wide variety of renal fuels on uptake of p-aminohippuric acid (PAH) and uric acid (UA) by separated rabbit renal tubules. PAH and UA uptakes in 15 min over a range of substrate concentrations of 0.01-10.2 mM were determined. All tricarboxylic acid cycle intermediates and pyruvate showed biphasic stimulation of PAH and UA uptake. .alpha.-Ketoglutarate produced a 320 .+-. 54% increase in PAH uptake and a 192 .+-. 60% increase in UA uptake at 0.16 mM, the concentration at which uptake was maximal, while causing 20 .+-. 3 (PAH) and 35 .+-. 7% (UA) inhibition at 10.2 mM. Citrate produced a 373 .+-. 19% increase in PAH uptake and a 246 .+-. 41% increase in UA uptake at 0.64 mM. PAH and UA uptake were also stimulated by acetate, glucose, fructose, phosphoenolpyruvate and L-glutamic acid. A direct relationship between stimulation of PAH and UA transport and stimulation of renal cortical oxidative metabolism was found.