Urate transport in the nephron

This paper summarizes the literature on the sties of urate transport, secretory and reabosrptive, in the nephron. In the animals studied thus far the bulk of urate transport occurs in the proximal tubules. Two patterns of transport have been uncovered. In one, urate is secreted and reabsorbed throughout the convoluted tubule (perhaps the pars recta as well). The direction of net transport depends on the kind of animal studied and in some instances on the experimental conditions. In the second pattern there is a strong secretory process in the pars recta, and net secretion of urate, when it occurs, is attributable to that segment. In some but not all animals it is clear that urate secretion in the proximal tubules occurs by a mechanism separate from that which secretes p-aminohippurate (PAH). One important unresolved question is: How general is the occurrence of separate secretory mechanisms for PAH and urate? Another unresolved question is: What are the magnitudes of the unidirectional fluxes of urate in the segments in which bidirectional transport occurs?