Micropuncture study of uric acid transport in rat kidney.

Free-flow micropuncture studies were perfromed to evaluated uric acid transport in the rat kidney. In all studies (a-minus 14C) uric acid and (methoxy-3H) inulin wereadministered. A simple two-step, column-chromatographic technique was utilized to separate (2-minus 14C) uric acid from its labeled oxidation product in plasma, urine, and tubular fluid. Tubular fluid collections were obtained from the early-and late-proximal tubule under control conditions and during subsequent volume expansion induced with 0.9 per-cent sodium chloride. These studies indicate bidirectional, possible active, uric acidtransport in the proximal tubule undr control conditions, with net reabsorption evident early and net decretion apparent late in this nephron segment. In association with volumeexpansion net uric acid reabsorption and secretion both decreased. No significant nettransport was evident beyond the accessible portion of the late-proximal tubule in either experimental state.