In a previous study we have found that acetylcholine, a renal vasodilator, inhibits fractional and absolute reabsorption of sodium in the proximal tubule of the dog. To delineate whether this effect on proximal tubular sodium reabsorption was related to alterations in renal hemodynamics or to a direct tubular action of the drug, free-flow micropuncture studies were performed in the dog in which the tubular fluid to plasma inulin ratio and nephron filtration rate were determined before and during the administration of a structurally different renal vasodilator, bradykinin. This agent increased sodium excretion from 12 to 96 μEq/min and decreased total kidney filtration fraction from 0.35 to 0.25. However, sodium reabsorption in the proximal tubule of the superficial nephrons was unchanged during bradykinin administration.
Jay H. Stein, Rolando C. Congbalay, Dennis L. Karsh, Richard W. Osgood, Thomas F. Ferris