Renal transit times and distribution volumes of T-1824, creatinine, and water

¹ Department of Medicine, New York University School of Medicine, and Third and Fourth Medical Divisions, Bellevue Hospital, New York City

The multiple indicator-dilution technique has been applied to a study of the vascular and extravascular volumes of the dog kidney in vivo. After probenecid, the venous outflow patterns of hippurate, iodopyracet, and chlorothiazide are nearly identical to those of creatinine. The patterns of fructose and diatrizoate are nearly identical to those of creatinine under control conditions. Creatinine's distribution is flow limited and not diffusion limited, and its accessible volume is the extracellular volume of the kidney. The distribution volume of inulin is smaller owing either to diffusion limitation or to an excluded volume phenomenon. At renal blood flows of 6 ml/sec per 100 g kidney, the vascular volume averages 20.5 ml blood and the interstitial fluid volume 20.0 ml equivalent plasma/100 g kidney. From experiments with labeled water, cell water averages 38.7 g/100 g kidney. The ratio of interstitial fluid to cell water averages 0.56. The distribution volume of sodium falls between that of water and that of creatinine. Some limitations of indicator-dilution experiments are indicated.

Key Words: renal vascular volume • renal interstitial compartment volume • renal cell water • indicator-dilution studies inulin • fructose • diatrizoate • iodopyracet • probenecid • sodium 22 • tritiated water

Submitted on August 31, 1964