Relative Renal Excretion Patterns of Sodium Ion, Chloride Ion, Urea, Water and Glomerular Substances

Abstract

Excretion patterns of sodium (Na 22) and chloride (Cl 36) ions, water (as deuterium or tritium oxides), and urea (labeled with C14) were determined relative to the excretion patterns of simultaneously injected creatinine following nearly instantaneous injection into one renal artery of the dog followed by sampling of urine from each ureter separately for 30 periods each of 30 seconds duration. From the amount excreted in each period, corrected for recirculation, the amount injected and the time after injection there is obtained a time-fractional excretion relationship called the excretion pattern. The pattern for urea is lower than that of creatinine and slightly displaced; there is excess urea excretion in the later periods. Some of the urea that has entered tubular cells may return to the tubular lumen. For water there is found an excess excretion in the early periods and in the later periods. The later excess may represent water which has followed a pathway similar to that of urea. Patterns of Na and Cl ions are similar to each other but markedly displaced relative to the pattern for creatinine. The appearance time, modal transit time, and mean transit time of these ions are less by approximately 30 seconds than the corresponding transit times of creatinine. Only 25% and generally less of the eventually excreted creatinine is in the urine when 50% of the eventually excreted Na and Cl ions is in the urine. It is concluded that a major fraction of the Na and Cl ions and a substantial fraction of water bypass a portion or portions of the tubular system on passage from the renal artery to the bladder.