STUDIES OF UPTAKE AND RUNOUT OF p-AMINOHIPPURATE AND N-METHYLNICOTINAMIDE IN DOG RENAL SLICES

¹ Department of Pharmacology, State University of New York, Upstate Medical Center, Syracuse, New York

The mechanisms for the uptake and runout of p-aminohippurate (PAR) and N-methylnicotinamide (NMN) in dog renal slices have been shown in previous work to be different. To further characterize the differences in the transport of these two substances, the effects of temperature, pH, ionic composition of medium and inhibitors were determined. PAH runout increased with temperature over the range 0-40°C. PAH uptake increased more rapidly with increasing temperatures but showed a temperature optimum at 25°C. With NMN both runout and uptake were increased with temperature, the uptake being more temperature-sensitive. Varying pH from 6.5 to 82 had little effect on runout of either compound but the rates of uptake of both were increased the higher the pH until a pH optimum was reached with PAH. Removal of calcium or potassium from medium did not affect runout but decreased uptake rates and slice/medium ratios for both. lodoacetate and dinitrophenol inhibited the uptake of PAH and NMN, but iodoacetate had no effect on the runout of NMN. Similarly, Dibenamine, a specific irreversible inhibitor of the uptake of NMN, had no effect on the runout of NMN. These findings have been taken as further evidence that the transport mechanism for runout is different from the uptake process for both of these compounds in dog renal slices.