Transfer of Na transport inhibition in proximal tubules from saline volume-expanded to nonexpanded rats

In dual micropuncture experiments the shrinking drop technique was used to measured volume flux with artificial tubular fluid alternating with harvested tubular fluid during saline volume-expanded (VE) and nonexpanded periods. It is concluded that during VE, a transferable Na transport inhibitor appears in proximal tubular fluid, which together with a changed proximal tubular epithelium, possibly due to physical forces, accounts for proximal tubular Na transport inhibition during VE.