Micropuncture study of PAH and Diodrast transport in Necturus kidney

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Abstract
Net reabsorption and net secretion of p-aminohippurate (PAH) and iodopyracet (Diodrast) were previously reported in renal clearance studies on the salamander Necturus maculosus. In the present study, micropuncture techniques were used to localize the sites of tubular transport of these organic acids. In Necturus kidneys perfused with oxygenated Ringer solution, net PAH reabosrption was found in the proximal tubule. Such reabsorption was depressed in summer animals. Kidneys of intact Necturi extensively reabsorbed both PAH and Diodrast. Net Diodrast secretion by the proximal tubule was induced by high plasma PAH concentrations. When Diodrast solutions were microinjected into single proximal tubules, Diodrast was completely reabsorbed, provided injected amounts were not excessive. PAH in microinjected solutions inhibited Diodrast reabsorption. The results support the existence of active reabsorptive and secretory pumps for Diodrast in the Necturus kidney proximal tubule. Incidentally, the liver, not the kidneys, appears to be the major route of Diodrast excretion in this species.

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