Analysis of electrolyte movement in thin Henle's loops of hamster papilla

Abstract

Saline solutions isolated between oil droplets within the lumen of thin limbs of Henle's loops remained at constant volume, while raffinose solutions underwent a continuous volume increase with time. After equilibrium, composition of the NaCl perfusates with respect to osmolality and Na and Cl concentrations became similar to that of vasa recta plasma. These results were identical for both ascending and descending limbs and suggest that neither segment transports salt actively. Descending limbs and vasa recta were isopotential under all conditions; the ascending limb during antidiuresis is 9 mv negative, the collecting ducts 17 mv negative. Ascending limb negativity was abolished by osmotic diuresis or stopped-flow microperfusion with saline. Measurement of ion concentrations showed that the ascending limb potential of antidiuresis is not a diffusion potential, and that its disappearance during osmotic diuresis is not due to the appearance of a diffusion potential of countersign. We suggest that the ascending limb potential is a streaming potential, but that the collecting duct potential reflects active ion transport.