THE THEORY OF URINE FORMATION IN WATER DIURESIS WITH IMPLICATIONS FOR ANTIDIURESIS

摘要

We investigate a model of the renal medulla in which active NaCl transport is restricted to thick ascending limb of Henle's loop. The model contains a vas rectum, a loop of Henle, salt, and water. The model generates interstitial osmolality curves consonant with the known functioning of the kidney in water diuresis. Using data from the white rat and the curves gener¬ated by the mode1, one can predict the permeability of the thin limb of Henle's loop to NaCl and the percentage of total renal blood flow entering the inner medulla. In this model interstitial osmolality at the papilla can be about twice plasma osmolality, so that NaCl transport restricted to the outer medulla can contribute significantly to the work required in producing a hypertonic urine. However, the interstitial osmolality monotonically decreases proceeding from the junction of the outer and inner medulla to the papilla and the maximum interstitial osmolality in the outer medulla is greater than the maximum inter¬stitial osmolality in the inner medulla. Thus we infer that a source of active transport located in the inner medulla is needed to explain the high osmolali¬ties observed in hydropenia. A sketch of an alternative model, a "lineal multi¬plication mechanism", for the renal concentrating process is presented in which active transport in the inner medulla is restricted to active salt transport by the collecting duct. The lineal multiplication mechanism makes no use of counter-current multipliers in the inner medulla.