Distal tubular sodium and water resorption in man.

It is possible to quantitatively estimate Na and water transport by each segment of the human nephron during maximal water diuresis (MWD) with a newly developed technique. The present study describes a new development whereby Na reabsorption by the ascending limb of Henle's Loop can be measured during a test of maximal antidiuresis (TMA) and compared with that obtained in separate experiments during MWD. In experiments performed on eight subjects, Henle's Loop reabsorption, expressed as equivalent volume of solute-free water generated, was 23.9 +/- 3.7 during MWD, 24.5 +/- 2.3 ml/min/100 ml GFR in TMA, p greater than 0.05; r = 0.68, p less than 0.05. Thus, our new method is reproducible and theoretically correct.