Osmotically induced changes in electrical resistance of distal tubules of rat kidney

Changes in peritubular oncotic pressure do not alter the electrical resistance of distal convoluted tubules. Transverse specific electrical resistance decreases along the distal convoluted tubule in nondiuretic rats. This drop in resistance can be at least in part accounted for by the relative increae in osmolality of late distal fluid. Osmotic gradients influence the magnitude of intercellular rather than transcellular conductance. Hyposmolality of tubular fluid leads to reduced shunting, whereas increased tubular osmolality has the opposite effect. The osmotic effect forms part of an intraepithelial positive feedback loop for sodium reabsorption in the diluting segment of the renal nephron.