Permeability of the loop of Henle, vasa recta, and collecting duct to water, urea, and sodium.

MORGAN, TREFOR, AND ROBERT MT. BERLINER. Permeability of the loop of Henle, uasu recta, and collecting duct to water, urea, and sodium. Am. J. Physiol. 215(l): 108-115. 1968.-The permeability of the loops of Henle, collecting ducts, and vasa recta have been studied by free-flow perfusion. When ADH was absent the diffusional permeability coefficient for THO in the descending limb (DL) was I 19 ZII 14 (SE) cm se0 X lo-“, ascending limb (AL) 50 =t 4.5 collecting duct (CD) 45 =t 3.1, and vasa recta (VR) at least 192 & 20. ADH increased the value for collecting ducts to 87 + 7 without changing the other values. The diffusional permeability coefficients for urea were DL 13 =t 3.0; AL 14 =t 2.0; CD 20 + 1.3; and VR 47 + 3.3. ADH increased the permeability of the CD (30 + 2.4) without affecting the other structures. The permeability of the descending limb changed before the hairpin bend. Net water flux was DL 58 + 6.2 nliters cmm2 milliosmoF min-I, AL 4.4 + 1.1; CD (no ADH) 4.2 zk 2.2; CD (ADH) 30 + 2.6. All parts of the nephron were relatively impermeable to mannitol but were permeable to urea. NaCl did not enter the collecting duct or ascending limb but entered the descending limb of Henle’s loop. These observations are consistent with what would be predicted if the driving force of the countercurrent system were a sodium pump in the ascending limb of the loop of Henle, although such a pump was not demonstrated in this preparation.